Microbial Diversity and Pathogenesis Flashcards
How do microbes avoid soluble immunity factors?
- Avoid complement fixation
- Destroy Ab
- Avoid eliciting/detection by Ab
How is Toxoplasmosis diagnosed?
- Serology (ELISA for anti-toxiplasma serum antibodies) - blood test
- PCR
- Histology (detection of tissue cysts) or gross pathology (retina)
Define
Merozoites
a small amoeboid sporozoan trophozoite (as of a malaria parasite) produced by schizogony that is capable of initiating a new sexual or asexual cycle of development
True or False:
Normal flora can become pathogenic
True
These are termed opportunistic pathogens
Definition
lacking a cell nucleus
Anucleate cells
True or False:
Toxoplasma infect phagocytes by being phagocytosed
False
The invade the phagocytes
Definition
an infection caused by pathogens (bacteria, viruses, fungi, or protozoa) that take advantage of an opportunity not normally available, such as a host with a weakened immune system, an altered microbiota (such as a disrupted gut microbiota), or breached integumentary barriers
Opportunistic pathogens
Define
Phage therapy
the therapeutic use of bacteriophages to treat pathogenic bacterial infections
Definition
symbiosis which is beneficial to both organisms involved
Mutualism
What are human mycoses caused by?
True fungal pathogens and opportunistic pathogens
What are the differences between prokaryotes and eukaryotes?
What causes Giardiasis?
- G. intestinalis*
- G. lamblia*
Definition
the cells and tissues of a host that support growth of a particular virus or bacterium
Tissue tropism
Define
E. coli
a bacterium commonly found in the intestines of humans and other animals, some strains of which can cause severe food poisoning
Definition
DNA sequences that can move around the genome, changing their number of copies or simply changing their location, often affecting the activity of nearby genes
Mobile genetic element
Define
Anucleate cells
lacking a cell nucleus
Define
16S rRNA
the component of the 30S small subunit of a prokaryotic ribosome that binds to the Shine-Dalgarno sequence
What is the normal flora of the lower respiratory tract?
It does not usually have microbiota
Definition
molecules shared by groups of related microbes that are essential for the survival of those organisms and are not found associated with mammalian cells
PAMPs
What is the bulk of the cell wall comprised of in Acid-fast bacteria?
Unique types of lipids such as mycolic acid
Definition
starting from the beginning
De novo
The relationship between the normal flora and the host is:
Select one:
a. mutualistic and parasitic
b. symbiotic
c. paratism and commensalism
d. commensalism and mutalism
The relationship between the normal flora and the host is:
Select one:
a. mutualistic and parasitic
b. symbiotic
c. paratism and commensalism
d. commensalism and mutalism
What does viral protain VP16 do in class 1 viruses?
Stimulates cellular reverse transcriptase to transcribe IE genes
How do viruses lyse cells?
Viroporins - hydrophobic proteins, interact with and disrupt membranes
Picornaviruses - VP2
Which section of the IgA molecule does IgA protease cleave?
The hinge region
Definition
recovering from an illness or medical treatment
Convalescent
Define
Resident flora
The microorganisms that usually occupy a particular body site
Definition
a compound present in the walls of Gram-positive bacteria. It is a polymer of ribitol or glycerol phosphate
Teichoic acid
Define
Adhesins –
cell-surface components or appendages of bacteria that facilitate adhesion or adherence to other cells or to surfaces, usually the host they are infecting or living in
What is unique to Mycoplamataceae bacteria?
They completely lack a cell wall
Definition
any of a group of spore-producing organisms feeding on organic matter, including moulds, yeast, mushrooms, and toadstools
Fungi
Definition
a common bacterium that lives on the skin or in the nose and in most situations it is harmless. However, if it enters the body through a cut in the skin, it can cause a range of mild to severe infections, which may cause death in some cases. Also known as S. aureus
Golden staph
Define
Invasins
Any of a class of proteins associated with the penetration of bacteria into mammalian cells
Definition
a carbohydrate-enriched coating that covers the outside of many eukaryotic cells and prokaryotic cells, particularly bacteria
Glycocalyx
Describe spherical viruses
Icosahedral ordered symmetry
Formed by repeating units of protein
A regular polyhedron with 20 triangular faces
Define
Operon
a unit made up of linked genes which is thought to regulate other genes responsible for protein synthesis
Definition
an organism consisting of a cell or cells in which the genetic material is DNA in the form of chromosomes contained within a distinct nucleus. They include all living organisms other than the eubacteria and archaea
Eukaryotes
Definition
a supergroup of protists that are defined by an asymmetrical appearance with a feeding groove that is “excavated” from one side; it includes various types of organisms which are parasitic, photosynthetic and heterotrophic predators
Excavata
Define
A-B toxins –
two-component protein complexes secreted by a number of pathogenic bacteria. They can be classified as Type III toxins because they interfere with internal cell function
What stimulates transcription of early genes in class 1 viruses?
IE gene proteins
What makes up most of the cell wall of a Gram-positive bacteria?
Peptidoglycan
Definition
a major constituent of the cell wall of gram-positive bacteria
Lipoteichoic acid
What is the step-wise gene expression of viruses?
Immediate early
Early
Late (Assembly and egress)
Definition
the capsid of a virus with the enclosed nucleic acid
Nucleocapsid
What is the ideal media to grow bacteria from the respiratory tract?
Horse blood agar
Definition
a microscopic parasite that causes the diarrheal illness known as giardiasis
Giardia
True or False:
Candida albicans can form biofilms
True
How is Toxoplasmosis transmitted?
Ingestion of raw/undercooked cyst-infected meat
Contaminated drinking water
Ingestion of raw/undercooked vegetables
Ingestion of cat feces
Describe the pathogenesis of Giardiasis
- Cysts undergo developmental change in duodenum and form trophozoites
- Trophozoites attach to duodenal epithelial cells via a sucking disk
- Feed on mucosal secretions and grow and multiply, interfering with intestinal absorption
Define
Transcytosis
a type of transcellular transport in which various macromolecules are transported across the interior of a cell
Definition
a blood protein produced in response to and counteracting a specific antigen. They combine chemically with substances which the body recognizes as alien, such as bacteria, viruses, and foreign substances in the blood
Antibodies (Ab) –
Bacterial siderophores:
Select one:
a. Act as receptors for nitrogen-binding host proteins
b. Are high molecular weight membrane proteins
c. Allow the normal flora to out-compete pathogens
d. Are used to chelate iron in the environment
Bacterial siderophores:
Select one:
a. Act as receptors for nitrogen-binding host proteins
b. Are high molecular weight membrane proteins
c. Allow the normal flora to out-compete pathogens
d. Are used to chelate iron in the environment
Eukaryotes
Select one:
a. Carry out all it’s functions through the cytoplasmic membrane
b. Have a membrane delimited nucleus
c. are only bacteria
d. mycolic acid on the cell wall
Eukaryotes
Select one:
a. Carry out all it’s functions through the cytoplasmic membrane
b. Have a membrane delimited nucleus
c. are only bacteria
d. mycolic acid on the cell wall
Definition
a protein released by animal cells, usually in response to the entry of a virus, which has the property of inhibiting virus replication.
Interferon
True or False:
The vast majority of DNA sequences in human blood are viral
True
Definition
a type of transmission that occurs when bacteria or viruses travel on dust particles or on small respiratory droplets that may become aerosolized when people sneeze, cough, laugh, or exhale
Airborne transmission
Definition
a differential stain used to identify acid-fast organisms such as members of the genus Mycobacterium
Acid-fast stain
Definition
infection with candida, especially as causing oral or vaginal thrush
Candidiasis
Adhesion is mediated by which structures?
- Pili/fibriae
- Afibrial adhesins
- Bacterial capsules
Definition
the most common bacterial cytotoxic proteins and are required for virulence in a large number of important pathogens that generally disrupt host cell membranes, but they can have additional effects independent of pore formation
Pore-forming toxins
How can Toxoplasmosis be prevented?
- Wear gloves when gardening, carefull cleaning of cat litter trays especially if you are pregnant (or thinking about it)
- Wash hads properly
- Cook all meat thoroughly
- Wash (and peel) your veggies (selected countries)
- Clean surfaces and kitchen utensils to prevent cross-contamination
Define
Transient flora
Microbes inhabiting a body surface or cavity for a brief period of time, usually as a result of their promotion and selection by antibiotic therapy, chemotherapy, hospitalization, illness, or surgery
Definition
a thin but robust layer of mucilage adhering to a solid surface and containing a community of bacteria and other microorganisms
Biofilms
Definition
infections that have been caught in a hospital and are potentially caused by organisms that are resistant to antibiotics
Noscomial infections
Define
Asymptomatic carrier
a person or other organism that has become infected with a pathogen, but that displays no signs or symptoms
What are the three main vectors for horizontal gene transfer?
Plasmids
Bacteriophages
Transposons
Definition
a gene that protects a cell from one step on the path to cancer
Tumour-supressor gene
What is the name of a parasitic organism that lives within the host?
Endoparasite
Define
Bacteriocins
a protein produced by bacteria of one strain and active against those of a closely related strain
What happens in cerebral malaria?
The infected RBCs obstruct the blood vessels in the brain
Define
Gram positive
bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their cell wall.
Define
De novo
starting from the beginning
Definition
the transmission of pathogens through vehicles such as water, food, and air
Vehicle transmission
Definition
the type of ribosome found in bacteria and archaea that are comprised of a small 30S subunit and large 50S subunit
70S ribosome
Define
Antibodies (Ab) –
a blood protein produced in response to and counteracting a specific antigen. They combine chemically with substances which the body recognizes as alien, such as bacteria, viruses, and foreign substances in the blood
What are the three protein exotoxins?
Membrane-disrupting toxins
A-B toxins
Superantigens
What is considered the 5th Koch’s postulate?
Effective therapeutic or preventative measure(s) should eliminate disease
How is cryptosporidium prevented?
- Exclude people with Cryptosporidium infection from childcare, preschool, school and work until there has been no diarrhea for 24 hours
- People who have diarrhea should not use swimming pools or spas for 14 days after the symptoms have stopped
- Pasterurisation and boiling as control measures
- Wash hands
Define
Virulence factor
Factor(s) required by the microorganism that enable it to cause disease
How can bacteria inhibit the phagolysosome?
- Block fusion to lysosomes
- Lyse phagosomal membrane
- Block/be resistant to acidification
- Block assemblt of NADPH oxidase
Define
Incubatory
the period between exposure to an infection and the appearance of the first symptoms
True or False:
Fungi can produce spores through both sexual or asexual life cycles
True
Define
Toxoplasmosis
a disease caused by toxoplasmas, transmitted chiefly through undercooked meat, soil, or in cat faeces. Symptoms of infection generally pass unremarked in adults, but can be dangerous to unborn children.
Definition
A chain of easily disrupted fungal cells that is intermediate between a chain of budding cells and a true hypha, marked by constrictions rather than septa at the junctions
Elogate pseudohyphae
What are the two major parts of the LPS later?
Lipid A
O-specific polysaccharide side chain (O antigen)
Cryptosporidium oocysts are resistant to what and susceptible to what?
Resistant to chlorination but are killed by conventional cooking or boiling
Define
Trophozoites
a growing stage in the life cycle of some sporozoan parasites, when they are absorbing nutrients from the host
What are the common nematode parasites that infect humans?
Roundworms
Hookworms
Pin or threadworms
Which areas do bacteria colonise that have poor access for antibodies?
Inside cells
Epidermis
CNS
Gall bladder
Cysts
What do endospores contain?
DNA, ribosomes and large amounts of dipicolinic acid in the core (aids dormancy)
Define
Macrophages
a large phagocytic cell found in stationary form in the tissues or as a mobile white blood cell, especially at sites of infection
Most fungal pathogens of humans are opportunistic, which means that:
Select one:
a. They infect a host at first contact
b. They need to switch morphology
c. They mostly infect immunosuppressed subjects
d. They require a specific infection route
Most fungal pathogens of humans are opportunistic, which means that:
Select one:
a. They infect a host at first contact
b. They need to switch morphology
c. They mostly infect immunosuppressed subjects
d. They require a specific infection route
How is Cryptosporidium transmitted?
From animal reservoirs in contaminated food or water (manu birds and mammal shed oocysts in feces)
Definition
a type of transcellular transport in which various macromolecules are transported across the interior of a cell
Transcytosis
Definition
an organism that makes ATP by aerobic respiration if oxygen is present, but is capable of switching to fermentation or anaerobic respiration if oxygen is absent
Faculative anaerobes
Define
Archaea
microorganisms which are similar to bacteria in size and simplicity of structure but radically different in molecular organization. They are now believed to constitute an ancient group which is intermediate between the bacteria and eukaryotes
Definition
any unicellular fungus that reproduces vegetatively by budding or fission, including forms such as candida that can cause disease
Yeast
The Plaque Assay:
Select one:
a. A) Is based on the fact that infection is latent in the majority of infected cells, leading to the formation of plaques of dead cells only by the non-latent viruses.
b. A) Is based on the fact that each virion initially infects a single cell, and its progeny infects neighbouring cells, leading to the formation of a plaque of dead cells.
c. Provides a measure of the efficiency of viral replication
d. Provides a measure of the size of the viral genome.
The Plaque Assay:
Select one:
a. A) Is based on the fact that infection is latent in the majority of infected cells, leading to the formation of plaques of dead cells only by the non-latent viruses.
b. A) Is based on the fact that each virion initially infects a single cell, and its progeny infects neighbouring cells, leading to the formation of a plaque of dead cells.
c. Provides a measure of the efficiency of viral replication
d. Provides a measure of the size of the viral genome.
Define
S. epidermidis
a gram-positive, coagulase-negative cocci that is a part of our skins normal flora
Where are Toxoplasma cysts activated?
In the gut
How is Malaria transmitted?
Malaria parasites are transmitted from one person to another by the female Anopheles mosquito. The males do not transmit the disease as the feed only on plant juices
What is the eclipse period?
Stage where no new viruses are present in host cells
Define
Pathogenicity
the property of causing disease
How can bacteria avoid being recognised or inhibit internalisation?
- Avoiding opsonisation
- Forming capsules (hides PAMPs)
- Forming biofilms
Definition
an organism that lives in or on an organism of another species (its host) and benefits by deriving nutrients at the other’s expense
Parasites
What cells do Toxoplasma infect?
Invasion of multiple cells types including moncytes, macrophages, dendritic cells
True or False:
Viruses are only able to grow within a cell
False
Viruses do not grow, but they can only assemble within cells
What is the life cycle of a roundworm
Definition
a unit made up of linked genes which is thought to regulate other genes responsible for protein synthesis
Operon
Definition
collection of nucleic acids, both RNA and DNA, that make up the viral community associated with a particular ecosystem or holobiont
Virome
True or False
Disease causing toxins may be found in the cell wall of a bacteria
False
Disease causing toxins may be found in the outer membrane of a bacteria
Definition
the genetic material of a bacteriophage, incorporated into the genome of a bacterium and able to produce phages if specifically activated
Prophage
Define
Bacteriophages
a virus which parasitizes a bacterium by infecting it and reproducing inside it
Definition
distinct class of genomic islands acquired by microorganisms through horizontal gene transfer. They are found in both animal and plant pathogen
Pathogenicity island
Definition
a staining technique for the preliminary identification of bacteria, in which a violet dye is applied, followed by a decolorizing agent and then a red dye. The cell walls of certain bacteria (denoted Gram-positive ) retain the first dye and appear violet, while those that lose it (denoted Gram-negative ) appear red
Gram stain
What are A-B toxins and what do they do?
Binary toxins with a catalytic ‘warhead’ (A) and a targeting component (B). It causes post-translational modifications of polypeptides
E. coli is not present in all humans
Select one:
True
False
E. coli is not present in all humans
Select one:
True
False
Definition
Any of many parasitic protozoans, of the class Sporozoa, that reproduce alternately sexually and asexually via spores; they are responsible for diseases such as malaria
Sporozones
Definition
bacteria that cannot live outside the host cell
Obligate intracellular pathogens
How do bacteria avoid eliciting or detection by antibodies?
- Remain inside host cells
- Host mimicry
- Coat with host proteins
- Colonise sites with poor access for antibodies
- Keep ahead of the immune system
Which enzymes needed by viruses to convert their nucleic acid into mRNA must be encoded by the virus itself?
RNA-dependent RNA polymerase
RNA-dependent reverse transcriptase
How do you treat Candidiasis?
- There is no satisfactory treatment currently
- Antifungals used for cutaneous lesions and systemic candidiasis
Define
Lytic cycle
one of the two cycles of viral reproduction that results in the destruction of the infected cell and its membrane
What makes up the bacterial cytoplasm?
Cytosol
Nucleoid - chromosome
Ribosomes
Inclusion bodies (e.g. endospores)
Cytoskeletal components
Definition
small masses of lymphatic tissue found throughout the ileum region of the small intestine
Peyer’s Patch
Define
Naked virus
A virus lacking the viral envelope
Define
Cytopathic
structural changes in host cells that are caused by viral invasion
What are the symptoms of Cryptosporidiosis?
Diarrhea
Stomach pain
Nausea
Fever
Fatigue
Define
Acid-fast bacteria
bacteria with a cell wall rich in special acids, called mycolic acids
When are virulence genes expressed?
When the bacteria sense a specific niche or in response to population density
How many types of viruses are considered in the Baltimore Classification Scheme?
7
Why do antibiotics that target ribosomes not effect human cells?
The antibiotics act on the 70S ribosomes unit but has no effect on the 80S units found in human cells
How are healthy individuals treated for Toxoplasmosis?
- Usually no treatment necessary, symptoms abate within weeks to months
- But… infection leads to chronic infection (may need later treatment)
- Most cases go undiagnosed and remain clinically unapparent
Definition
the severity or harmfulness of a disease or poison
Virulence
Define
Infection
a proliferation of a harmful strain of bacteria on or inside the body
Define
Plasmid
a genetic structure in a cell that can replicate independently of the chromosomes, typically a small circular DNA strand in the cytoplasm of a bacterium or protozoan
Define
Prophage
the genetic material of a bacteriophage, incorporated into the genome of a bacterium and able to produce phages if specifically activated
True or False:
(-) ssRNA viruses, but not (+) ssRNA viruses must deliver RNA-dependent RNA polymerase protein with genome
True
Define
Excavata
a supergroup of protists that are defined by an asymmetrical appearance with a feeding groove that is “excavated” from one side; it includes various types of organisms which are parasitic, photosynthetic and heterotrophic predators
Koch’s postulates are four criteria that are used to determine whether a disease is caused by a particular microorganism. Which of the following is not a postulate?
Select one:
a. The pathogen must be found in all cases of disease
b. The pathogens must be cultured outside the host in the laboratory
c. The pathogen must cause disease in a healthy animal
d. The pathogen must be tested in humans to determine whether it causes disease
e. The pathogen should be re-isolated from the test animal
Koch’s postulates are four criteria that are used to determine whether a disease is caused by a particular microorganism. Which of the following is not a postulate?
Select one:
a. The pathogen must be found in all cases of disease
b. The pathogens must be cultured outside the host in the laboratory
c. The pathogen must cause disease in a healthy animal
d. The pathogen must be tested in humans to determine whether it causes disease
e. The pathogen should be re-isolated from the test animal
Definition
an association between two organisms in which one benefits and the other derives neither benefit nor harm
Commensalism
True or False:
It is not possible to become infected with Giardia through contact with blood
True
Cysts form in gut
Define
Lipopolysaccharide (LPS) layer
the major component of the outer membrane of Gram-negative bacteria
Staphylococcus epidermidis is present in all human beings
Select one:
True
False
Staphylococcus epidermidis is present in all human beings
Select one:
True
False
Where does the Plasmodium develop in the mosquito?
The Plasmodium develops in the gut of the mosquito and is passed on in the saliva of an infected infect
Define
Pilin
a class of fibrous proteins that are found in pilus structures in bacteria
Approximately __% of pathogens known to affect humans are zoonotic
Approximately 70% of pathogens known to affect humans are zoonotic
Definition
the infection specificity of certain pathogens to particular hosts and host tissues
Host tropism
Why is Toxoplasmosis particularly dangerous for pregnant women?
Parasites (tachyzoites) can cross the placenta to the foetus
What percentage of microbes are pathogenic?
Less than 5%
Definition
a gram-positive, coagulase-negative cocci that is a part of our skins normal flora
S. epidermidis
Definition
a parasitic flatworm; a tapeworm.
Cestodes
Definition
a toxin that cause host cells to lyse by forming pores in plasma membrane
Membrane-distrupting toxins
Define
Microorganisms
a microscopic organism, especially a bacterium, virus, or fungus.
Define
Periplasmic space
a concentrated gel-like matrix in the space between the inner cytoplasmic membrane and the bacterial outer membrane called the periplasmic space in gram-negative bacteria
Definition
a relict, nonphotosynthetic plastid found in most protozoan parasites belonging to the phylum Apicomplexa
Apicoplast
Draw the Baltimore Classification Scheme diagram
Definition
the complete, infective form of a virus outside a host cell, with a core of RNA and a capsid
Virions
What is a biofilm?
a group of organisms living in a hydrated polymeric matrix
Define
Fungi
any of a group of spore-producing organisms feeding on organic matter, including moulds, yeast, mushrooms, and toadstools
Define
O antigen
an antigen that occurs in the body of a gram-negative bacterial cell
What is the name of an organism that can grow in the presence or absence of oxygen?
Faculative anaerobe
What happens when Plasmodium sporozotes infect humans?
Sporozotes are carried by the blood to the liver where they form cyst-like structures containing thousands of merozoites. After 9-16 days they return to the blood and penetrate the red blood cells, where they multiply again, progressively breaking down the RBCs
How do naked viruses egress?
Lysis
True or False:
The normal flora is well developed in the womb
False
The fetus is sterile in the womb
Definition
a virus which parasitizes a bacterium by infecting it and reproducing inside it
Bacteriophages
Define
Commensalism
an association between two organisms in which one benefits and the other derives neither benefit nor harm
Where are the coat proteins of enveloped and naked viruses found?
Bound to receptors of the capsid of naked viruses and the glycoproteins of enveloped
Definition
a Gram-positive, round-shaped bacterium that is a member of the Firmicutes, and it is a usual member of the microbiota of the body, frequently found in the upper respiratory tract and on the skin
S. aureus
Definition
an abnormal form of a normally harmless protein found in the brain that is responsible a variety of fatal neurodegenerative diseases
Prions
Definition
a person or other organism that has become infected with a pathogen, but that displays no signs or symptoms
Asymptomatic carrier
Definition
the period between exposure to an infection and the appearance of the first symptoms
Incubatory
What features fo archaea share with Eukarya?
- DNA replication, transcription and translation seems more like that of Eukarya
- Archaea DNA has histones
- Many enzymes involved in DNA replication are similar to those found in Eukarya
An Asymptomatic carrier is one:
Select one:
a. who harbours the pathogen but does not show any symptoms of the disease
b. who is free of the pathogen
c. who is infected by the pathogen and is in the process of being sick with the disease
d. whose has the antibodies against the disease causing agent
An Asymptomatic carrier is one:
Select one:
a. who harbours the pathogen but does not show any symptoms of the disease
b. who is free of the pathogen
c. who is infected by the pathogen and is in the process of being sick with the disease
d. whose has the antibodies against the disease causing agent
Why do we study viruses?
- Viruses infect all living things
- We eat and breathe billions of virions regularly
- We carry viral genomes as part of our own genetic material
- Viruses drive Global Cycles
What are the four basic shapes of bacteria?
Cocci
Bacilli
Spirochaete
Comma’s
How can Toxoplasmosis alter host behaviour?
Possibly linked to a parasite encoded tyrosine hydroxylase that mimics dopamine and therefore modifies behaviour
Where are extracellular parasites found?
Blood, intestines or genito-urinary system?
Definition
a protein structure found at the base of a eukaryotic undulipodium (cilium or flagellum)
Basal body
Definition
The microorganisms that usually occupy a particular body site
Resident flora
Define
Tissue tropism
the cells and tissues of a host that support growth of a particular virus or bacterium
Define
Exotoxins
a toxin released by a living bacterial cell into its surroundings
Define
Basal body
a protein structure found at the base of a eukaryotic undulipodium (cilium or flagellum)
Attachment or adhesion is mediated by:
1 – capsule
2 – cell wall
3 – cytoplasmic membrane
4 – invasins
5 – fimbriae
6 – ribosomes
Select one:
a. 1 & 6
b. 2 & 4
c. 3 & 5
d. 1 & 5
Attachment or adhesion is mediated by:
1 – capsule
2 – cell wall
3 – cytoplasmic membrane
4 – invasins
5 – fimbriae
6 – ribosomes
Select one:
a. 1 & 6
b. 2 & 4
c. 3 & 5
d. 1 & 5
Definition
a large phylum of parasitic alveolates. Most of them possess a unique form of organelle that comprises a type of plastid called an apicoplast, and an apical complex structure
Apicomplexa
Define
Glycocalyx
a carbohydrate-enriched coating that covers the outside of many eukaryotic cells and prokaryotic cells, particularly bacteria
What is the lifecycle of a hookworm?
Define
Virulence
the severity or harmfulness of a disease or poison
How do enveloped viruses egress?
Budding
Define
Dipicolinic acid
a chemical compound which composes 5% to 15% of the dry weight of bacterial spores. It is implicated as responsible for the heat resistance of the endospore.
Define
Parasitism
relationship between two species of plants or animals in which one benefits at the expense of the other, sometimes without killing the host organism
True or False:
There are no vaccines available for any parasites
True
Define
Yeast
any unicellular fungus that reproduces vegetatively by budding or fission, including forms such as candida that can cause disease
What are the three types of symbiotic bacteria-human relationships?
Mutualism
Commensalism
Parasitism
In what ways do bacteria avoid complement fixation?
Having a capsule - prevents fixation
Secreting complement degrading molecules
Bind antibody by Fc receptor (upside down)
Define
30S ribosome
the smaller subunit of the 70S ribosome found in prokaryotes. It is a complex of the 16S ribosomal RNA (rRNA) and 19 proteins
The resident flora of a person will not cause disease in humans
Select one:
True
False
The resident flora of a person will not cause disease in humans
Select one:
True
False
What are the Molecular Koch’s postulates?
- The virulence gene is always found in strains within a particular virulence phenotype
- The gene should be expressed in the host
- Mutation (inactivation) of that particular gene abolishes the virulence phenotype
- Reintroduction of the gene reconstitutes the virulence phenotype
Definition
Any of a class of proteins associated with the penetration of bacteria into mammalian cells
Invasins
Definition
infection of the intestine with a flagellate protozoan, Giardia, which causes diarrhoea and other symptoms
Giadiasis
Definition
An agent that destroys or causes the expulsion of parasitic intestinal worms.
Anthelminthics
Define
Reverse transcriptase
an enzyme which catalyses the formation of DNA from an RNA template in reverse transcription.
Definition
An enzyme that catalyzes the splitting of a phospholipid molecule by the addition of water
Phospholipases
Define
Acute carrier
an infected individual who is not obviously diseases. Can be incubatory or convalescent
Define
Acid-fast stain
a differential stain used to identify acid-fast organisms such as members of the genus Mycobacterium
What are the two most common bacteria present in all humans?
- Staphylococcus epidermidis*
- Escherichia coli*
Definition
the removal of moisture from something
Dessication
Prions are proteins that cause microbial diseases
Select one:
True
False
Prions are proteins that cause microbial diseases
Select one:
True
False
Define
Comma’s
any curved-rod shaped bacterium
Define
Nematode
a worm of the large phylum Nematoda, such as a roundworm or threadworm
Define
Zoonoses
a disease which can be transmitted to humans from animals
Define
Candida albicans
an opportunistic pathogenic yeast that is a common member of the human gut flora. It can also survive outside the human body. It is detected in the gastrointestinal tract and mouth in 40–60% of healthy adults
Define
Apicoplast
a relict, nonphotosynthetic plastid found in most protozoan parasites belonging to the phylum Apicomplexa
Definition
any of a group of RNA viruses which insert a DNA copy of their genome into the host cell in order to replicate, e.g. HIV.
Retrovirus
Define
Interferon
a protein released by animal cells, usually in response to the entry of a virus, which has the property of inhibiting virus replication.
What happens when Toxoplasma faces pressure from the immune system?
They form slow-replicating bradyzoites
True or False:
E. coli is an example of a bacteria that engages in mutualism with humans
True
Define
Convalescent
recovering from an illness or medical treatment
What are the symtoms of Toxoplasmosis in immunocompromised or pregnant individuals?
- Severe and serious pathological consequences
- Immunocompromised individuals
- Severe Toxoplasmosis involving gut, eye, heart, brain and other organ damage
- Pregnant women
- Foetus abnormalities
- Can develop from acute infection or reactivation of cysts after infection earlier in life
Which of the following questions regarding bacterial invasion is true?
Select one:
a. Can involve the injection of bacterial effector proteins into the host cell by a type 3 secretion system
b. The zipper mechanism is mediated in an “inside-out” manner following bacterial binding to host cell surface molecules
c. Is dependent on spontaneous formation of membrane protrusions
d. A specific interaction with the host cell is not required
Which of the following questions regarding bacterial invasion is true?
Select one:
a. Can involve the injection of bacterial effector proteins into the host cell by a type 3 secretion system
b. The zipper mechanism is mediated in an “inside-out” manner following bacterial binding to host cell surface molecules
c. Is dependent on spontaneous formation of membrane protrusions
d. A specific interaction with the host cell is not required
Definition
referring to an RNA strand that can serve directly as messenger RNA and be transcribed into DNA
Positive sense
Where in the body are Candida normally found?
They normally reside in the intestinal tract and can be found on mucous membranes and skin withou causing infection
Definition
a lipid component of an endotoxin held responsible for the toxicity of gram-negative bacteria. It is the innermost of the three regions of the lipopolysaccharide (LPS), also called endotoxin molecule, and its hydrophobic nature allows it to anchor the LPS to the outer membrane
Lipid A
Definition
bacteria with a cell wall rich in special acids, called mycolic acids
Acid-fast bacteria
Define
Drenching
forcibly administer a drug in liquid form orally to (an animal)
Definition
the cause, set of causes, or manner of causation of a disease or condition
Aetiology
Definition
a rod-shaped bacterium
Bacilli
What are the enzymes that are used by viruses to convert there nucleic acid into mRNA? What do these enzymes do?
RNA-dependent reverse transcriptase: Converts RNA into DNA
RNA-dependent-RNA polymerase: Replicates RNA from RNA template
DNA-dependent polymerase: Replicates DNA from DNA template
What is the name of a parasitic organism that lives on the surface of its host?
Ectoparasite
Definition
a chemical compound which composes 5% to 15% of the dry weight of bacterial spores. It is implicated as responsible for the heat resistance of the endospore.
Dipicolinic acid
Define
Pathogenicity island
distinct class of genomic islands acquired by microorganisms through horizontal gene transfer. They are found in both animal and plant pathogen
Define
Pore-forming toxins
the most common bacterial cytotoxic proteins and are required for virulence in a large number of important pathogens that generally disrupt host cell membranes, but they can have additional effects independent of pore formation
Define
Prions
an abnormal form of a normally harmless protein found in the brain that is responsible a variety of fatal neurodegenerative diseases
What secondary cell polymers are found in the cell wall of a Gram-positive bacteria?
Teichoic acid
Lipoteichoic acid
Which are usually more environmentally stable: Enveloped or naked viruses?
Naked viruses
Definition
bacteria that do not retain the crystal violet stain used in the gram-staining method of bacterial differentiation
Gram negative
Definition
a protein present in milk and other secretions, with bactericidal and iron-binding properties
Lactoferrin
Gram-negative bacteria have a complex outer membrane. What does it contain?
Proteins
Lipoproteins
Phopholipids
Lipopolysaccharides
Non-transducing retrovirus can cause cancer by:
Select one:
a. Integration into the genome near to a tumour suppressor gene, enhancing its expression
b. Integration within a proto-oncogene, silencing its expression
c. Sequestration of a tumour suppressor protein by viral early gene E7
d. Integration into the genome near to an oncogene, enhancing its expression
Non-transducing retrovirus can cause cancer by:
Select one:
a. Integration into the genome near to a tumour suppressor gene, enhancing its expression
b. Integration within a proto-oncogene, silencing its expression
c. Sequestration of a tumour suppressor protein by viral early gene E7
d. Integration into the genome near to an oncogene, enhancing its expression
Define
Opportunistic pathogens
an infection caused by pathogens (bacteria, viruses, fungi, or protozoa) that take advantage of an opportunity not normally available, such as a host with a weakened immune system, an altered microbiota (such as a disrupted gut microbiota), or breached integumentary barriers
Definition
four criteria designed to establish a causative relationship between a microbe and a disease
Koch’s postulates
What is the most common type of plant pathogen?
Fungi
What specialised organelles do Apicomplexa have?
Apicoplast
Apical complex
Define
Flagellum
a slender threadlike structure, especially a microscopic appendage that enables many protozoa, bacteria, spermatozoa, etc. to swim
What are the typical layers of a virus?
- Nucleic acid (DNA or RNA)
- Protein shell/capsid
- (Other layers ‘matrix’)
- (Envelope with glycoprotein)
Define
Positive sense
referring to an RNA strand that can serve directly as messenger RNA and be transcribed into DNA
Antibody-dependent enhancement (ADE)
occurs when non-neutralizing antiviral proteins facilitate virus entry into host cells, leading to increased infectivity in the cells
Definition
A virus lacking the viral envelope
Naked virus
Definition
a class of fibrous proteins that are found in pilus structures in bacteria
Pilin
Bacteria that completely lack a peptidoglycan layer will have what result in a Gram stain?
Stains Gram negative
Definition
a resistant asexual spore that develops inside some bacteria cells
Endospores
What is the function of the cell wall of a bacteria?
- Maintains shape of the bacterium
- Provides strong structural support
- Preventing bursting or collapsing due to osmotic pressure
- Attachment site
- Can contribute to pathogenicity
- Can protect the cell from toxic substances
- Site of action of some antibiotics
Activation of the right operon (lytic genes) causes what in viruses?
Expression of lysis genes for replication, lysis and assembly
Repression of left operon promotor
What are the two types of membrane-disrupting toxins?
Phospholipases
Pore-forming toxins
Definition
a worm of the large phylum Nematoda, such as a roundworm or threadworm
Nematode
Definition
the therapeutic use of bacteriophages to treat pathogenic bacterial infections
Phage therapy
Define
Lactoferrin
a protein present in milk and other secretions, with bactericidal and iron-binding properties
How can you get a giardia infection?
- Swallowing Giardia picked up fro msurfaces that contain faeces from an infected person or animal
- Drinking water or using ice made from water sources where Giardia may live
- Swallowing water while swimming or playing in water where Giardia could be present
- Eating uncooked food that contains Giardia organisms
- Having contact with someone who is ill with giardiasis
- Travelling to countries where giardiasis is endemic
Definition
forcibly administer a drug in liquid form orally to (an animal)
Drenching
Definition
a large phagocytic cell found in stationary form in the tissues or as a mobile white blood cell, especially at sites of infection
Macrophages
Definition
Microbes inhabiting a body surface or cavity for a brief period of time, usually as a result of their promotion and selection by antibiotic therapy, chemotherapy, hospitalization, illness, or surgery
Transient flora
What are the major impediments for the multiplication and dissemination of bacteria?
Immune system
Normal flora
Availability of nutrients
What shaped bacteria are most likely to produce endospores?
Bacilli
Define
Teichoic acid
a compound present in the walls of Gram-positive bacteria. It is a polymer of ribitol or glycerol phosphate
True or False:
Most parasites are eukaryotic
True
Define
Pili
a hair-like appendage found on the surface of many bacteria and archaea
Definition
an antigen that occurs in the body of a gram-negative bacterial cell
O antigen
Define
Nucleoid
an irregularly shaped region within the cell of a prokaryote that contains all or most of the genetic material, called genophore
True or False:
Viruses are considered obligate intracellular parasites
True
Where are intracellular parasites found?
In a wide variety of cells (RBCs, macrophages, epithelial cells, brain, muscle etc.)
Define
Germination
the process in which a spore begins to grow vegetative cells, and sporeling hyphae
Definition
chemotrophs that are heterotrophic organisms. They are not capable of fixing carbon to form their own organic compounds
Chemoheterotrophs –
What is the primary host of Toxoplasma?
Wild and domestic cats
Definition
a strain of Methicillin-resistant bacteria.
MRSA
Definition
a bacterium commonly found in the intestines of humans and other animals, some strains of which can cause severe food poisoning
E. coli
What are the four Koch’s postulates?
- The microbe must be present in every case of the disease (and absent from healthy hosts)
- The microbe must be isolated from the diseased hosts and grown in pure culture
- The disease must (should) be reprodiced when a pure culture is introduced into a healthy (susceptible) host
- The microbe must be revoerable from an experimentally-infected host
Define
IgA
an antibody that plays a crucial role in the immune function of mucous membranes
Which mechanism is this?
Zipper mechanism
Definition
a microscopic organism, especially a bacterium, virus, or fungus.
Microorganisms
What are the 3 main structural forms of a virus?
Spherical
Helical
Complex
Describe helical viruses
Rod shaped coat
Multiple repeating copies of protein coated onto the genome
Hollow tube, like a spiral staircase
Define
Ectoparasite
parasitic organism that lives on the surface of its host
Define
S. aureus
a Gram-positive, round-shaped bacterium that is a member of the Firmicutes, and it is a usual member of the microbiota of the body, frequently found in the upper respiratory tract and on the skin
Define
Endospores
a resistant asexual spore that develops inside some bacteria cells
Define
Anthelminthics
An agent that destroys or causes the expulsion of parasitic intestinal worms.
Definition
any spherical or roughly spherical bacterium
Cocci
Define
70S ribosome
the type of ribosome found in bacteria and archaea that are comprised of a small 30S subunit and large 50S subunit
Definition
nuclear or cytoplasmic aggregates of stable substances, usually proteins. They typically represent sites of viral multiplication in a bacterium or a eukaryotic cell and usually consist of viral capsid proteins
Inclusion bodies
Definition
A normal gene which, when altered by mutation, becomes an oncogene that can contribute to cancer
Protooncogenes
Define
Sex pilus
structure that allow for the transfer of DNA between bacteria, in the process of bacterial conjugation
When does Candida cause symptoms?
Overgrowth of these organisms
Define
Peyer’s Patch
small masses of lymphatic tissue found throughout the ileum region of the small intestine
Define
Prokaryotes
a microscopic single-celled organism which has neither a distinct nucleus with a membrane nor other specialized organelles, including the bacteria and cyanobacteria
How does a virus switch from lysogenic to lytic?
SOS pathway
Produces protease (recA) following DNA damage which degrades repressor of lytic pathway
Lytic pathway activates and predominates
How do extracellular protic parasites evade the immune system?
Avoiding recognisition of their plasma membrane
- Antigenic variation of surface antigens
- Polymorphisms in dominant surface antigens
- Degrading complement
Which mechanism is this?
Trigger mechanism
Define
Dessication
the removal of moisture from something
What are the two phases of a virus life cycle?
Virion phase
Infected cell phase
Definition
microorganisms which are similar to bacteria in size and simplicity of structure but radically different in molecular organization. They are now believed to constitute an ancient group which is intermediate between the bacteria and eukaryotes
Archaea
Define
Baltimore Classification Scheme
a virus classification system that groups viruses into families, depending on their type of genome (DNA, RNA, single-stranded (ss), double-stranded (ds), etc..) and their method of replication
What bacteria produce superantigens?
Staph aureus
Strep pyogenes
Define
Obligate intracellular pathogens
bacteria that cannot live outside the host cell
What is the growth limiting nutirent for bacteria?
Iron
Definition
the component of the 30S small subunit of a prokaryotic ribosome that binds to the Shine-Dalgarno sequence
16S rRNA
Define
MRSA
a strain of Methicillin-resistant bacteria.
Definition
an opportunistic pathogenic yeast that is a common member of the human gut flora. It can also survive outside the human body. It is detected in the gastrointestinal tract and mouth in 40–60% of healthy adults
Candida albicans
Define
Cocci
any spherical or roughly spherical bacterium
Define
Transposons
a chromosomal segment that can undergo transposition, especially a segment of bacterial DNA that can be translocated as a whole between chromosomal, phage, and plasmid DNA in the absence of a complementary sequence in the host DNA
The cell wall of Gram positive bacteria is thicker than that of Gram negative bacteria
Select one:
True
False
The cell wall of Gram positive bacteria is thicker than that of Gram negative bacteria
Select one:
True
False
Define
True hyphae
a long, branching filamentous structure of a fungus, oomycete, or actinobacterium
What features fo archaea share with bacteria?
- Anucleate cells
- Cell envelope
- Generally possess single circular chromosome
- Vary shape and size
Define
IgA protease
a highly specific 106kDa enzyme that cleaves amino acid sequences of certain proteins. The natural substrate of it is immunoglobulin A, hence its name
What is the largest roundworm parasitising the human intestine?
Ascaris lumbricoides
Define
Giadiasis
infection of the intestine with a flagellate protozoan, Giardia, which causes diarrhoea and other symptoms
Define
Faculative anaerobes
an organism that makes ATP by aerobic respiration if oxygen is present, but is capable of switching to fermentation or anaerobic respiration if oxygen is absent
Define
Viruses
an infective agent that typically consists of a nucleic acid molecule in a protein coat, is too small to be seen by light microscopy, and is able to multiply only within the living cells of a host
Define
Capsid
the protein shell of a virus
Definition
a microscopic single-celled organism which has neither a distinct nucleus with a membrane nor other specialized organelles, including the bacteria and cyanobacteria
Prokaryotes
Define
PAMPs
molecules shared by groups of related microbes that are essential for the survival of those organisms and are not found associated with mammalian cells
Mycobacterium tuberculosis is different to Gram positive and Gram negative bacteria in that it has:
Select one:
a. LPS
b. mycolic acid
c. peptidoglycan
d. cell membrane
Mycobacterium tuberculosis is different to Gram positive and Gram negative bacteria in that it has:
Select one:
a. LPS
b. mycolic acid
c. peptidoglycan
d. cell membrane
Definition
a flexible spirally twisted bacterium, especially one that causes syphilis
Spirochaete
What are the characteristics of the genus Staphylococcus?
- Gram positive cocci
- Form irregular clusters
- Non-motile
- Faculative anaerobes
- Catalase positive
Definition
the property of causing disease
Pathogenicity
How is (-) ssRNA converted into mRNA?
Needs to be converted into mRNA by RNA-dependent RNA polymerase
Define
Provirus
the genetic material of a virus as incorporated into, and able to replicate with, the genome of a host cell
Mariaus Demariaeii is a bacteria thought to cause an emerging hospital acquired infection frequently manifesting as necrotising fasciitis. It has been found that this bacterium frequently loses pathogenicity in culture. This is a limitation associated with which of Koch’s postulates?
Select one:
a. Postulate 2
b. Postulate 1
c. Postulate 3
d. Postulate 4
Mariaus Demariaeii is a bacteria thought to cause an emerging hospital acquired infection frequently manifesting as necrotising fasciitis. It has been found that this bacterium frequently loses pathogenicity in culture. This is a limitation associated with which of Koch’s postulates?
Select one:
a. Postulate 2
b. Postulate 1
c. Postulate 3
d. Postulate 4
Define
Apical complex
A group of cytoskeletal structures and associated membrane-bounded organelles found at the anterior end of adult obligate intracellular protozoan parasites in the phylum Apicomplexa
The peptidoglycan layer of Gram-negative bacteria is much thinner than Gram-positive bactera. What properties does this give Gram-negative bacteria?
Relatively greater flexibility
but sensitive to lysis
Define
Contact transmission
a type of infection transmission that involves direct or indirect interaction between organisms
Definition
a toxin released by a living bacterial cell into its surroundings
Exotoxins
Definition
the smaller subunit of the 70S ribosome found in prokaryotes. It is a complex of the 16S ribosomal RNA (rRNA) and 19 proteins
30S ribosome
Define
Vehicle transmission
the transmission of pathogens through vehicles such as water, food, and air
Define
Nucleocapsid
the capsid of a virus with the enclosed nucleic acid
Definition
the regulation of gene expression in response to fluctuations in cell-population density
Quorum sensing
True or False:
There are virtually no known Archaea pathogens of humans
True
Define
Giardia
a microscopic parasite that causes the diarrheal illness known as giardiasis
What are the two types of bacterial toxins?
Exotoxins
Endotoxins
Define
Enveloped virus
A virus that has an outer wrapping or envelope
True or False:
Bacteria that completely lack peptidoglycan are insensitive to penicillin
True
Definition
a small amoeboid sporozoan trophozoite (as of a malaria parasite) produced by schizogony that is capable of initiating a new sexual or asexual cycle of development
Merozoites
Define
Lipoteichoic acid
a major constituent of the cell wall of gram-positive bacteria
What are the limitations of Koch’s postulates?
- No host factors are taken into account (i.e. carrier states or opportunistic pathogens)
- Emphasis on ability to culture the organism
- Organisms can lose virulence/pathogenicity during laboratory cultre
- Disease may nor require the organism to infect the host (i.e. toxins)
- Requires a suitable/susceptible animal model
What are some examples of protozoan diseases?
Toxoplasmosis
Cryptosporidiosis
Giardiasis
Malaria
Define
Helminths
a parasitic worm; a fluke, tapeworm, or nematode
Define
Aetiology
the cause, set of causes, or manner of causation of a disease or condition
How can viruses cause cancer?
Activation of cellular oncogenes
Expression of their oncogenes
Inactivation of tumor supressors
Define
Myocolic acid
long fatty acids found in the cell walls of the Mycolata taxon, a group of bacteria that includes Mycobacterium tuberculosis, the causative agent of the disease tuberculosis
Definition
relationship between two species of plants or animals in which one benefits at the expense of the other, sometimes without killing the host organism
Parasitism
Which one of these is not present in prokaryotes
Select one:
a. cell wall
b. spore
c. cell membrane
d. nucleus
Which one of these is not present in prokaryotes
Select one:
a. cell wall
b. spore
c. cell membrane
d. nucleus
Define
Colonisation –
the presence of bacteria on a body surface (like on the skin, mouth, intestines or airway) without causing disease in the person
Definition
a virus classification system that groups viruses into families, depending on their type of genome (DNA, RNA, single-stranded (ss), double-stranded (ds), etc..) and their method of replication
Baltimore Classification Scheme
Definition
a very large structure of many bacteria. It is a polysaccharide layer that lies outside the cell envelope, and is thus deemed part of the outer envelope of a bacterial cell
Capsule
_____________: the sum of the number of healthy years of life lost due to ill health, disability and premature death
Disability Adjusted Life Years (DALYs): the sum of the number of healthy years of life lost due to ill health, disability and premature death
What part of the bacteria cell wall is unique to bacteria?
Pepidoglycan layer
How do bacteria evade phagocytes?
- Avoid being recognised or inhibit internalisation
- Kill the phagocyte/induce apoptosis (antiphagocyte toxins)
- Inhibition of phagolysosome (survive phagocytosis)
What are the two stages of Giardia lamblia?
Resistant cyst stage
Vegetative trophozoite stage
Definition
an infective agent that typically consists of a nucleic acid molecule in a protein coat, is too small to be seen by light microscopy, and is able to multiply only within the living cells of a host
Viruses
What is the Selective media to identify S. aureus?
Mannitol salt agar
Definition
parasitic organism that lives on the surface of its host
Ectoparasite
Define
Capsule
a very large structure of many bacteria. It is a polysaccharide layer that lies outside the cell envelope, and is thus deemed part of the outer envelope of a bacterial cell
What are the mechanisms of disease of viruses?
- Cell death (cytopathic)
- Immunipathology (overaggressive response)
- Immunosuppression
- Oncogenesis
How are pregnany/immunocompromised individuals treated for Toxoplasmosis?
Antibiotics
Definition
A virus that has an outer wrapping or envelope
Enveloped virus
Define
Complement –
a part of the immune system that enhances the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inflammation, and attack the pathogen’s cell membrane
Define
Histones
any of a group of basic proteins found in chromatin
Define
Eclipse period
the time between infection by (or induction of) a bacteriophage, or other virus, and the appearance of mature virus within the cell; an interval of time during which viral infectivity cannot be recovered
Define
Mutualism
symbiosis which is beneficial to both organisms involved
Definition
a growing stage in the life cycle of some sporozoan parasites, when they are absorbing nutrients from the host
Trophozoites
Define
Sporozones
Any of many parasitic protozoans, of the class Sporozoa, that reproduce alternately sexually and asexually via spores; they are responsible for diseases such as malaria
Define
Membrane-distrupting toxins
a toxin that cause host cells to lyse by forming pores in plasma membrane
How do Plasmodium reproduce?
Sexual reproduction: in anopheles mosquito
Asexual reproduction: in human (called sporozoans) in which sporozones multiply to produce merezoites, these, in turn, become trophozoites
Define
Superantigens
a class of antigens that result in excessive activation of the immune system. Specifically it causes non-specific activation of T-cells resulting in polyclonal T cell activation and massive cytokine release
Definition
a long, branching filamentous structure of a fungus, oomycete, or actinobacterium
True hyphae
Define
Mobile genetic element
DNA sequences that can move around the genome, changing their number of copies or simply changing their location, often affecting the activity of nearby genes
How do bacteria outcompete host cells for iron?
- Secreting very high affinity iron-chelators (siderophores) and have siderophore receptors to capture them
- Expressing high-affinity iron-binding membrane proteins
- Expressing receptors for iron capture proteins (e.g. lactoferrin, transferron) used by host
- Express toxins to release host Fe
Define
Endotoxins
a toxin present inside a bacterial cell that is released when it disintegrates
True or False:
Fimbriae are larger than pili
False
Pili are larger than fimbriae
Define
Retrovirus
any of a group of RNA viruses which insert a DNA copy of their genome into the host cell in order to replicate, e.g. HIV.
Define
Lysogenic
a bacterial cell which can produce and transfer the ability to produce a phage
Definition
structure that allow for the transfer of DNA between bacteria, in the process of bacterial conjugation
Sex pilus
What are the symptoms of Giardia infections?
Diarrhea
Gas
Greasy stool
Stomach cramps
Nausea
Dehydration
What surrounding the peptidoglycan layer is unique to Gram-negative bacteria?
Periplasmic space
What is the function and importance of the LPS layer?
- Contributes to the structural integrity of the outer membrane and forms a permeability barrier for certain chemicals
- Increases the negative charge of the cell membrane and helps stabilise overall memebrane structure
- Essential for bacterial survival - so possible therapeutic target
- Collectively highly immunogenic… but ‘molecular mimicry’ and rapid antigenic variation provided by the glycan O
- The lipid A portion is a major, potent endotoxin
Define
Gram negative
bacteria that do not retain the crystal violet stain used in the gram-staining method of bacterial differentiation
Definition
a disease caused by toxoplasmas, transmitted chiefly through undercooked meat, soil, or in cat faeces. Symptoms of infection generally pass unremarked in adults, but can be dangerous to unborn children.
Toxoplasmosis
Define
Chemoheterotrophs –
chemotrophs that are heterotrophic organisms. They are not capable of fixing carbon to form their own organic compounds
Definition
a genetic structure in a cell that can replicate independently of the chromosomes, typically a small circular DNA strand in the cytoplasm of a bacterium or protozoan
Plasmid
Define
Lysis
the disintegration of a cell by rupture of the cell wall or membrane.
Which part of the cell do most viruses replicate?
Nucleus
How do intracellular protists evade the immune system?
By hiding inside a cell
Definition
long fatty acids found in the cell walls of the Mycolata taxon, a group of bacteria that includes Mycobacterium tuberculosis, the causative agent of the disease tuberculosis
Myocolic acid
Capsules play an essential role in bacterial pathogenesis because they:
Select one or more:
a. Are involved in bacterial motility
b. Are involved in the transfer of genetic material
c. Prevent phagocytosis
d. Allow evasion of antigen-specific antibody responses
e. Cause sepsis
f. Prevent osmotic lysis
g. Are involved in adhesion
Capsules play an essential role in bacterial pathogenesis because they:
Select one or more:
a. Are involved in bacterial motility
b. Are involved in the transfer of genetic material
c. Prevent phagocytosis
d. Allow evasion of antigen-specific antibody responses
e. Cause sepsis
f. Prevent osmotic lysis
g. Are involved in adhesion
Definition
a subunit of the capsid, an outer covering of protein that protects the genetic material of a virus
Capsomeres
Which one of the following describes the three structural types of a viral capsid?
Select one:
a. Helical, complex or icosahedral.
b. Spherical, icosahedral or complex
c. Helical, dodecahedral or complex
d. Complex, helical or cubic.
Which one of the following describes the three structural types of a viral capsid?
Select one:
a. Helical, complex or icosahedral.
b. Spherical, icosahedral or complex
c. Helical, dodecahedral or complex
d. Complex, helical or cubic.
What are the symtoms of Toxoplasmosis in healthy individuals?
- Acute systemic inflammatory response (mostly clinically unapparent)
- Most common ‘flu-like’, swollen lymph glands, muscle/bone aches and pains
- Infrequent, severe GI involvement associated with parasite infection
- Symptoms often resolve quickly but result in a chronic infection with formation of tissue cysts; may or may not be symptomatic depending on the location of the cysts
Definition
a class of antigens that result in excessive activation of the immune system. Specifically it causes non-specific activation of T-cells resulting in polyclonal T cell activation and massive cytokine release
Superantigens
The Baltimore Scheme classifies viruses based on what?
- Nature of genome nucleic acid
- Mechanisms to generate mRNA (and replicated the genome)
- How they make more genome
What causes Cryptosporidiosis?
Cryptosporidium infection
What happens during the intestinal phase of roundworm?
The intestinal phase causes malnourishment, intestinal blockage. It will move around the body in response to chemotherapy or fever. Typically occurs 6 - 8 weeks after initial exposure
Definition
an irregularly shaped region within the cell of a prokaryote that contains all or most of the genetic material, called genophore
Nucleoid
Definition
a person or other organism that has been infected with a pathogen for a long time who may or may not be symptomatic
Chronic carrier
True or False:
Viruses all evolved from a single common ancestor
False
Define
Quorum sensing
the regulation of gene expression in response to fluctuations in cell-population density
Definition
Factor(s) required by the microorganism that enable it to cause disease
Virulence factor
Definition
a parasitic coccidian protozoan found in the intestinal tract of many vertebrates, where it sometimes causes disease.
Cryptosporidium
Which structure confers host specificity?
Tip of the pilus
Definition
the process in which a spore begins to grow vegetative cells, and sporeling hyphae
Germination
‘Blueberry muffin’ skin is typical of which condition?
Congenital toxoplasmosis
Which of the following AB toxin(s) are associated with alterations in muscle function?
Select one or more:
a. Botulinum toxin
b. Tetanus toxin
c. Diphtheria toxin
d. Cholera toxin
Which of the following AB toxin(s) are associated with alterations in muscle function?
Select one or more:
a. Botulinum toxin
b. Tetanus toxin
c. Diphtheria toxin
d. Cholera toxin
Definition
a disease caused by any fungus that invades the tissues, causing superficial, subcutaneous, or systemic disease
Human mycoses
What do virulence factors mediate?
- Colonisation of de novo niches in the body
- Adhesion (ligands for host cell-expressed proteins)
- Invasion
- Immune evasion mechanisms (e.g. bacterial capsules)
- Tissue damage (toxins)
Definition
a type of infection transmission that involves direct or indirect interaction between organisms
Contact transmission
Describe complex viruses
Large viruses; mixture of shapes, no consistent symmetry
Define
Lipid A
a lipid component of an endotoxin held responsible for the toxicity of gram-negative bacteria. It is the innermost of the three regions of the lipopolysaccharide (LPS), also called endotoxin molecule, and its hydrophobic nature allows it to anchor the LPS to the outer membrane
Define
Tumour-supressor gene
a gene that protects a cell from one step on the path to cancer
Which one of these features is present in a Gram negative bacterium but absent in a Gram positive bacterium?
Select one:
a. Peptidoglycan layer
b. Periplasmic space
c. cytoplasmic membrane
d. LPS layer
Which one of these features is present in a Gram negative bacterium but absent in a Gram positive bacterium?
Select one:
a. Peptidoglycan layer
b. Periplasmic space
c. cytoplasmic membrane
d. LPS layer
What is the difference between the CG content of pathogenicity islands compared to host DNA?
There is less C+G in pathogenicity islands
Definition
the presence of bacteria on a body surface (like on the skin, mouth, intestines or airway) without causing disease in the person
Colonisation –
Define
Virome
collection of nucleic acids, both RNA and DNA, that make up the viral community associated with a particular ecosystem or holobiont
Viruses cannot grow outside their host cells.
Select one:
True
False
Viruses cannot grow outside their host cells.
Select one:
True
False
Definition
an enzyme which catalyses the formation of DNA from an RNA template in reverse transcription.
Reverse transcriptase
Definition
a substance forming the cell walls of many bacteria, consisting of glycosaminoglycan chains interlinked with short peptides
Peptidoglycan
Definition
a strain of Staphylococcus aureus that is resistant to the antibiotic called vancomycin
VRSA
Definition
cell-surface components or appendages of bacteria that facilitate adhesion or adherence to other cells or to surfaces, usually the host they are infecting or living in
Adhesins –
Define
Host tropism
the infection specificity of certain pathogens to particular hosts and host tissues
How does latent infection occur?
VP16 and HCF in cytoplasm of neurons (instead of nucleus)
Causes IE genes to be repressed
Latency associated transcript (LAT) expressed
LAT promotes heterochromatic formation
Genome associates with heterochromatin
Commensal bacteria could become a pathogen through acquisition of virulence factors by?
Select one:
a. Infection with a lytic bacteriophage
b. Excision of a pathogenicity island
c. Quorum sensing to adapt to life in a biofilm
d. Integration of a transposon
Commensal bacteria could become a pathogen through acquisition of virulence factors by?
Select one:
a. Infection with a lytic bacteriophage
b. Excision of a pathogenicity island
c. Quorum sensing to adapt to life in a biofilm
d. Integration of a transposon
Where do Cryptosporidium undergo their sexual cycle?
In the vertebrate host (no insect vector)
How is (+) ssRNA converted into mRNA?
They are equivalent so can be directly translated by the cell
Define
Budding
a form of viral shedding by which enveloped viruses acquire their external envelope from the host cell membrane, which bulges outwards and encloses the virion
What are the four main modes of pathogen transmission?
Airborne
Contact
Vehicle
Vector borne
Define
Colicins
a bacteriocin produced by a coliform bacterium
Define
Inclusion bodies
nuclear or cytoplasmic aggregates of stable substances, usually proteins. They typically represent sites of viral multiplication in a bacterium or a eukaryotic cell and usually consist of viral capsid proteins
What causes Malaria?
Plasmodium infection
Define
Gram stain
a staining technique for the preliminary identification of bacteria, in which a violet dye is applied, followed by a decolorizing agent and then a red dye. The cell walls of certain bacteria (denoted Gram-positive ) retain the first dye and appear violet, while those that lose it (denoted Gram-negative ) appear red
Definition
the disintegration of a cell by rupture of the cell wall or membrane.
Lysis
Definition
any of a group of basic proteins found in chromatin
Histones
Definition
one of the two cycles of viral reproduction that results in the destruction of the infected cell and its membrane
Lytic cycle
Definition
a bacteriocin produced by a coliform bacterium
Colicins
How do bacteria mimic host cells to avoid antibodies?
Make capsules with sugars mimicking host surface glycoproteins
In class 1 viruses, where does the reverse transcriptase for early genes come from?
The viral genome
Definition
a slender threadlike structure, especially a microscopic appendage that enables many protozoa, bacteria, spermatozoa, etc. to swim
Flagellum
A Gram stain was carried out it was observed that bacteria appeared purple in colour and appeared as cocci in clusters. Given this information which one of the genus would this bacteria most likely belong to:
Select one:
a. Bacillus
b. Streptococcus
c. Escherichia
d. Staphylococcus
A Gram stain was carried out it was observed that bacteria appeared purple in colour and appeared as cocci in clusters. Given this information which one of the genus would this bacteria most likely belong to:
Select one:
a. Bacillus
b. Streptococcus
c. Escherichia
d. Staphylococcus
Definition
the time between infection by (or induction of) a bacteriophage, or other virus, and the appearance of mature virus within the cell; an interval of time during which viral infectivity cannot be recovered
Eclipse period
Antibodies may neutralise bacteria by:
Select one:
a. Lysing them with the assistance of complement
b. Preventing them from secreting toxin molecules
c. Preventing their attachment to cell surfaces
d. Causing them to agglutinate.
Antibodies may neutralise bacteria by:
Select one:
a. Lysing them with the assistance of complement
b. Preventing them from secreting toxin molecules
c. Preventing their attachment to cell surfaces
d. Causing them to agglutinate.
Define
Bacilli
a rod-shaped bacterium
What are the four steps in bacteria causing disease?
- Exposure
- Adherance
- Penetration/invasion
- Colonisation and growth
Define
Parasites
an organism that lives in or on an organism of another species (its host) and benefits by deriving nutrients at the other’s expense
Describe the life cycle of Giardia
What are the two types of food born disease?
True infection (slow response)
Intoxication (immediate response)
What is a viron called that isn’t surrounded by a membrane? What is it called when it is?
Nucleocapsid = Naked Virus
Nucleocapsid + membrane = Enveloped Virus
Define
Apicomplexa
a large phylum of parasitic alveolates. Most of them possess a unique form of organelle that comprises a type of plastid called an apicoplast, and an apical complex structure
Define
Koch’s postulates
four criteria designed to establish a causative relationship between a microbe and a disease
Define
Endoparasite
parasitic organism that lives within the host
Define
Eukaryotes
an organism consisting of a cell or cells in which the genetic material is DNA in the form of chromosomes contained within a distinct nucleus. They include all living organisms other than the eubacteria and archaea
Definition
a proliferation of a harmful strain of bacteria on or inside the body
Infection
Definition
a chromosomal segment that can undergo transposition, especially a segment of bacterial DNA that can be translocated as a whole between chromosomal, phage, and plasmid DNA in the absence of a complementary sequence in the host DNA
Transposons
Define
Phospholipases
An enzyme that catalyzes the splitting of a phospholipid molecule by the addition of water
What are the 5 basic steps of viral cell infection?
- Attachment: Enter host organism, ‘recognise’ specific target cell/tissue: attach to correct host cell
- Penetration/uncoating: Uncoating/release/exposure of genome payload: access to cellular components
- Gene expression/replication: Synthesis of virion components (Protein and nucleic acid)
- Assembly of virions: Self-assembly of structural subunits (genome and protein); packaging of nucleic acid, maturation
- Release of virions (budding, lysis etc.)
Why is the presence of D-amino acids in the peptidoglycan layer importent to bacteria survival?
D-amino acids protect against degradation by most peptidases since peptidases only recognise L-isomers of AA residues
Define
Peptidoglycan
a substance forming the cell walls of many bacteria, consisting of glycosaminoglycan chains interlinked with short peptides
Definition
occurs when non-neutralizing antiviral proteins facilitate virus entry into host cells, leading to increased infectivity in the cells
Antibody-dependent enhancement (ADE)
Viruses are very useful to which areas of modern science?
Oncolytic virotherapy
Phage therapy
Reverse transcriptase
Viral gene therapy
Lentivirus transduction
Definition
an antibody that plays a crucial role in the immune function of mucous membranes
IgA
Definition
the major component of the outer membrane of Gram-negative bacteria
Lipopolysaccharide (LPS) layer
Which endotoxin often leads to septic shock? How?
LPS which contains Lipid A (which is highly toxic to all animals) stimulates release of IL-1 and TNF which is detected by Toll-like receptor 4 and initiates an innate inflammatory signalling cascade
What happens during the lung phase of roundworm?
A. lumbricoides is known as Ascaris pneumontis. In the lung it causes hemorrhage, inflammation, bacterial infection. It also causes allergy in areas with seasonal transmission. Typically occurs at 6-14 days after initial exposure
Definition
any curved-rod shaped bacterium
Comma’s
True or False:
Humans are very vulnerable to fungi
False
Humans are relatively resistant
Definition
two-component protein complexes secreted by a number of pathogenic bacteria. They can be classified as Type III toxins because they interfere with internal cell function
A-B toxins –
Define
Cryptosporidium
a parasitic coccidian protozoan found in the intestinal tract of many vertebrates, where it sometimes causes disease.
Definition
a part of the immune system that enhances the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inflammation, and attack the pathogen’s cell membrane
Complement –
Definition
A group of cytoskeletal structures and associated membrane-bounded organelles found at the anterior end of adult obligate intracellular protozoan parasites in the phylum Apicomplexa
Apical complex
Definition
a form of viral shedding by which enveloped viruses acquire their external envelope from the host cell membrane, which bulges outwards and encloses the virion
Budding
Definition
a protein produced by bacteria of one strain and active against those of a closely related strain
Bacteriocins
What are the advantages and disadvantages of parasitism to the parasite?
- Provision of nutrients (often essential) +
- Protection from environment, host immune system etc. +
- Host controls and regulates parasite growth and development (host immune system) -
Define
Bacteria
a member of a large group of unicellular microorganisms which have cell walls but lack organelles and an organized nucleus, including some which can cause disease
Definition
parasitic organism that lives within the host
Endoparasite
How do microbes avoid phagocytes?
Avoid recognition, internalisation, destruction or phagocytosis
Define
Biofilms
a thin but robust layer of mucilage adhering to a solid surface and containing a community of bacteria and other microorganisms
Definition
a disease which can be transmitted to humans from animals
Zoonoses
Activation of the left operon (lysogenic genes) causes what in viruses?
Expression of lysogeny genes including integrase
Repression of right operon promotor
Define
Human mycoses
a disease caused by any fungus that invades the tissues, causing superficial, subcutaneous, or systemic disease
Definition
a bacterial cell which can produce and transfer the ability to produce a phage
Lysogenic
Definition
a member of a large group of unicellular microorganisms which have cell walls but lack organelles and an organized nucleus, including some which can cause disease
Bacteria
What two mechanisms mediate bacterial invasion?
Zipper mechanism
Trigger mechanism
Definition
a highly specific 106kDa enzyme that cleaves amino acid sequences of certain proteins. The natural substrate of it is immunoglobulin A, hence its name
IgA protease
Definition
the genetic material of a virus as incorporated into, and able to replicate with, the genome of a host cell
Provirus
Define
Airborne transmission
a type of transmission that occurs when bacteria or viruses travel on dust particles or on small respiratory droplets that may become aerosolized when people sneeze, cough, laugh, or exhale
How are virulence factors acquired?
Through mobile genetic elements
What do superantigens do?
Cause T-cell activation without the antigen present. It does this by cross-linking MHC class II molecules on antigen-presenting cells and T-cell receptors on CD4+ T cells
True or False:
In bacterial germination, one spore gives rise to one cell
True
What feature of acid-fast bacteria makes it impenetrable to most organic molecules including antibiotics?
The thick waxy nature of the lipids in the cell wall
What is the function of bacterial capsules?
Physical barrier that protects the bacteria cell:
- Protect against desiccation
- Prevents bacteriophages from attachment and infection
- Protects against phagocytosis
How can the genetic material of viruses vary?
Some viruses have DNA; can be:
- Double-stranded (ds)
- Gapped
- Single-stranded (ss)
- Linear, circular
Other viruses have RNA; can be:
- Single-stranded (ss)
- Double-stranded (ds)
- Can be in positive (+) or negative (-) sense
- Can be a single piece (non-segmented)
- Can be mutliple pieces (segmented)
Definition
the protein shell of a virus
Capsid
Definition
a toxin present inside a bacterial cell that is released when it disintegrates
Endotoxins
Define
VRSA
a strain of Staphylococcus aureus that is resistant to the antibiotic called vancomycin
Define
Noscomial infections
infections that have been caught in a hospital and are potentially caused by organisms that are resistant to antibiotics
What does the life-cycle of Cryptosporidium include?
A single oocyst and a trophozoite stage
Define
Capsomeres
a subunit of the capsid, an outer covering of protein that protects the genetic material of a virus
Define
Cestodes
a parasitic flatworm; a tapeworm.
What is the lifecycle of a tapeworm?
Definition
a hair-like appendage found on the surface of many bacteria and archaea
Pili
Define
Elogate pseudohyphae
A chain of easily disrupted fungal cells that is intermediate between a chain of budding cells and a true hypha, marked by constrictions rather than septa at the junctions
What is the difference between resident flora and transient flora?
Resident flora is always present but transient flora is not
How do membrane-disrupting toxins work?
Lyse host cells by disrupting the integrity of their plasma membrane
What surrounds all viruses?
Capsid
What is the difference between transducing and non-transducing retroviruses?
Transducing:
- Inset within a protooncogene
- Transcribed together
- Carry a dominant oncogene
Non-transducing:
- Inserts near a protooncogene
- The provirus promotor activates a cellular oncogene in cis
Definition
an infected individual who is not obviously diseases. Can be incubatory or convalescent
Acute carrier
Define
Virions
the complete, infective form of a virus outside a host cell, with a core of RNA and a capsid
Define
Spirochaete
a flexible spirally twisted bacterium, especially one that causes syphilis
Which protein stimulates cellular DNA-dependent RNA polemerase to transcribe IE genes?
Viral protein VP16
What is the most common pathogenic Candida?
Candida albicans
Excavata have ______ plastids and _________ mitochondria
Excavata have no plastids and highly reduced mitochondria
Definition
a parasitic worm; a fluke, tapeworm, or nematode
Helminths
Definition
structural changes in host cells that are caused by viral invasion
Cytopathic
True or False:
Cryptosporidium have both an apicoplast and apical complex
False
They don’t have a apicoplast
Definition
a concentrated gel-like matrix in the space between the inner cytoplasmic membrane and the bacterial outer membrane called the periplasmic space in gram-negative bacteria
Periplasmic space
Define
Chronic carrier
a person or other organism that has been infected with a pathogen for a long time who may or may not be symptomatic
Define
Candidiasis
infection with candida, especially as causing oral or vaginal thrush
Define
Plasmodia
a parasitic protozoan of a genus which includes those causing malaria.
Define
Golden staph
a common bacterium that lives on the skin or in the nose and in most situations it is harmless. However, if it enters the body through a cut in the skin, it can cause a range of mild to severe infections, which may cause death in some cases. Also known as S. aureus
Define
Protooncogenes
A normal gene which, when altered by mutation, becomes an oncogene that can contribute to cancer
Definition
bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their cell wall.
Gram positive
Definition
a parasitic protozoan of a genus which includes those causing malaria.
Plasmodia
What are the different modes of transmission for protozoan parasites?
Insect/tick vectors
Ingestion of infective stage
Venereal transmission (STDs)
How strong is the adhesion formed by pili/fibriae and adhesins?
Afibrial adhesins: Strong
Pili/fimbriae: Loose
What is the most widespread and dangerous species of Plasmodium?
Plasmodium falciparum
Can lead to cerebral malaria
