Biol121 Flashcards
What are the main components of the coronavirus virion
Spike, nucleocapsid, membrane , envelope, RNA viral genome
What receptors is associated with sars-cov2?
ACE2 receptors on our cells
Why does SARS-Cov2 cause respiratory problems? What’s the difference between the fluid in moderate and severe cases?
It causes an accumulation of fluid in the alveoli which reduces gas exchange. The fluid is protein rich in severe cases
What did research focus on before 2002 about coronaviruses?
Animal coronaviruses and murine coronavirus ( to do with rats/mice)
What type of RNA is the RNA in a coronavirus?
Single stranded, non-segmented, positive sense genome
Describe the cytokine storm with respect to coronaviruses?
1) coronavirus infects lung cells
2) immune cells such as macrophages, produce cytokines after identifying the virus
3) cytokines attract more cells which produce more cytokines
4) this creates a cycle of inflammation
5) damage can occur via fibrin formation
6) weakened blood vessels lead to fluid seeping into the lungs and this reduces gas exchange. (Decreased SA)
If the group number of a microorganism is higher is it more or less pathogenic ?
More pathogenic
If there are a lot of ACE2 receptors in the colon, what is a likely symptom of this coronavirus?
Diarrhoea
Why can the cytokine storm cause self tissue damage ?
It is not specific like an antibody response
What are the 10 macro elements for bacteria?
C, H, N, O,P,S, K, Ca, Mg, Fe
Why is potassium important for bacteria?
It is essential for some of its enzymes
Why is Mg important for bacteria?
Stabilises ribosomes, membranes and DNA
Why is iron important for bacteria?
Part of enzymes and electron transport proteins
What are some advantages of microbes?
Food materials benefit or are required e.g fermented foods such as yogurt or sauerkraut
What are some problems of microbes?
Microbes grow well in food fit for human consumption
Food spoilage
Food borne disease
Why do we not know the true diversity of a sample by culture?
Not all bacteria from a sample can be cultured
What groups are not eukaryotes?
Bacteria, viruses, certain blue-green algae
What ancient group is an intermediate between bacteria and eukaryotes?
Archaea
What are some characteristics of Archaea?
1) presence of characteristics tRNAs and rRNAs
2) absence of peptidoglycan , often replaced by a largely proteinaceous coat
3) linked lipids built form phytanyl chains (
What domain are all disease causing prokaryotes ?
Bacteria
What is the typical size of a a virus?
0.01-0.2 micrometers
What is the typical size of Bacteria?
0.2-5 micrometers
What is the typical size of Eukaryotes?
5-100 micrometers
What is the size of the Yeast?
5-10 micrometers
What is the typical size of Algae?
10-100 micrometers
What is the typical size of Protists ?
50-1000 micrometers
What are properties of all cells ?
Compartmentalisation and metabolism , growth, evolution
What are properties of some cells?
Motility, differentiation (e.g spores) , communication
What are the functions of the bacterial cell membrane?
Separation of a cell from its environment
Selectively permeable barrier
Site of respiration and photosynthesis
Energy conservation ( proton motive force )
What is the purpose of the cell wall in bacteria?
Protects the cell wall from osmotic lysis and determines and maintains the shape of the bacteria.
What are the 3 types of bacterial cell clusters?
Diplococci (2) , streptococci (chain), clump of cocci
Does a gram-positive cell wall of bacteria have a thick or thin peptidoglycan wall ?
Thick
Gram negative bacterial cell walls have a a thin peptidoglycan wall, and an outer membrane composed of …….
Lipids, proteins, lipopolysaccharides
Describe the mycobacterial/ Archaeal cell walls.
S layer consisting of proteins and glycoprotein
After gram staining what colour do Gram negative appear?
Pink, don’t keep stain
What colour do gram positive bacteria appear after staining?
Purple, they keep their stain
How do antibiotics such as Penicillin affect cause bacteria to die?
Target peptidoglycan in cell wall. Lysozymes break G-M bonds, in the polymer chains linked via peptide bridges. Cell loses water so cannot function
Why doesn’t lysozyme / penicillin kill Archaea?
They lack peptidoglycan and they have a variety of cell walls including a pseudo-peptidoglycan
What is the purpose of the capsule?
Protection from host defences ( phagocytosis)
Protection from harsh environmental conditions (desiccation)
Attachment to surfaces
What is the function of Fimbriae?
Recognition and attachment to surfaces
What is the function of pili?
Similar looking to fimbriaea, required for mating
Polar flagellum
Flagellum at end of cell
Monotrichous
One flagellum
Monotrichous
One flagellum
Amphitrichous
One flagellum at each end of the cell
Lophotrichous
Cluster of flagella at one end or both ends
Peritrichous
Spread over entire surface of cell
Nucleoid
Irregularly shaped region, location of single or 2 chromosomes
Are plasmids independent of the chromosome in terms of growth and reproduction? Do they carry any any genes that provide a selective advantage?
Yes, they can exist and replicate independently of chromosome. Often they have genes that have antibiotic drug resistance.
What are cellular inclusions ?
Granules of organic or inorganic material that are reserved for future use.
Give some examples of cellular inclusions
Glycogen , PHB, poly phosphate granules , sulphur granules
What are gas vesicles used for?
Buoyancy in some aquatic bacteria ?
What are some advantages of endospores?
Highly resistant to heat, drying, radiation, and chemicals very low water content. Contain calcium dipicolinate- binds free water and helps to dehydrate the cell. Special proteins protect DNA
What are the micro elements for bacteria?
Copper, zinc, nickel, vanadium, selenium, etc
What are chemically defined media?
Media where the exact chemical composition is known
What is complex media?
Exact chemical composition is not known, it is made of digests of complex material such as milk protein, beef, soybeans, yeast etc
What is the name given to when 2 bacterial cells begin to divide?
A septum
What is the generation time?
The time needed for a population to double
Describe the phases of a typical growth curve for a bacterial population?
1)Lag phase (interval between inoculation and max division rate)
2)log phase ( exponential growth)
3)stationary phase (bacteria not reproducing but are alive, no nutrients left)
4)death phase
What are culturable bacteria?
Can be grown on media( liquid/solid)
What are viable cells?
Bacteria in a state of very low metabolic activity and do not divide but are alive. They can become culturable after resuscitation.
True or false. Every type of bacteria can be cultured on every type of media?
False
What is a total count, viable count and culturable count?
Counts cells that can form colonies on solid media or increase turbidity in liquid media
What are the advantages of direct microscopic counts for measuring bacterial growth?
Easy and fast
What are the disadvantages of direct microscopic counts for measuring bacterial growth?
Uses special microscope counting slide
Does not differential between live and dead bacteria
When measuring bacterial growth using agar plates what is the assumption?
Each culturable cell will grow and divide to yield one colony
What is cholera?
an acute, diarrheal illness caused by infection of the intestine with the toxigenic bacterium Vibrio cholerae serogroup O1 or O139.
What is the problem with testing water for cholera in countries with unsanitary supplies of water?
A negative test could be that cholera is not present but it also could mean that the cholera bacteria are viable but not culturable- so they are still pathogenic and not safe
What is the indirect method of measuring bacterial growth?
Measuring turbidity
What can be used to measure turbidity?
A spectrophotometer
What is the effect on the total cell count and viable/culturable count with a bacteriostatic agent?
Total and viable/culturable counts stay the same , no inc or dec
What is the effect on the counts for Bacteriocidal agents?
Total cell count stays same. Viable/culturable decreases
What is the effect of the bacteriolytic agents ?
Total, viable and culturable counts all decrease?
In terms of carbon sources what are a) heterotrophs b) autotrophs
Heterotrophs require organic molecules made by other organisms
Autotrophs, their main carbon sources is CO2
In terms of energy sources what are a) phototrophs b) chemotrophs
Phototrophs ) use light as energy sources
Chemotrophs) oxidise organic or inorganic compounds
What factors affect bacterial growth?
Oxygen, Temperature, pH, osmolarity
What are obligate aerobes ?
Bacteria that need O2 for growth
What are obligate anaerobes?
Bacteria that cannot grow in presence of oxygen
What are facultative anaerobes ?
Can grow with and without Oxygen
What are aerotolerant anaerobes?
Do not need oxygen but tolerate it
What are microaerophilic bacteria?
Bacteria that need oxygen but tolerate it only at low concentrations
What are psychrophiles?
Bacteria that grow best below 15 degrees , not above 20 and not below 0
What are mesophiles?
Bacteria that grow between 20-40 degrees , so many of our bacteria are mesophiles
What are thermophiles?
Grow best between 45-80 degrees , live in hot springs and compost heaps etc
What are hyperthermophiles?
Grow best above 80 degrees , live in hot springs
Do most bacteria prefer acidic, neutral or alkaline conditions?
Neutral
What are acidophiles and alkaliphiles?
Acidophiles grow best in acidic habitats. Alkaliphiles grow best in alkaline habitats
With respect to osmolarity what are halophiles?
Bacteria that grow in habitats with high salt concentrations, mild , moderate , extreme
Give a useful enzyme produced by thermophilic bacteria?
Taq polymerase, from Thermus aquaticus used for PCR
Define host
Organism which supports growth of viruses , bacteria and parasites
Define Pathogen
An organism that causes disease, by impairing or interfering with the normal physiological activities of the host
Define pathogenicity
The ability to cause disease
Define virulence
The degree or intensity of pathogenicity ( determined by toxicity and invasiveness)
Define infection
Bacteria persist in host without necessarily causing tissue damage
Define Disease
Damage to the host, parts of the body cannot fulfill their normal functions
What is the Miasma theory based upon?
The idea that disease comes from bad air, get rid of smells get rid of the diseases
What theory did Koch’s lab establish ? How did he come up with this theory?
-Germ theory of disease
- Koch’s postulates
- 1) Microorganisms are isolated from a diseased or dead animal.
2) the microorganisms are grown in pure culture
3) Microorganisms are identified
4) They are inoculated into a healthy lab animal
5) Disease is reproduced in the lab animal
6) The microorganisms are isolated from this animal and grown in pure culture
7) the microorganisms are identified
What is the difference between Opportunistic pathogens and Primary pathogens ? What word describes animal-human transmission?
-Opportunistic pathogens only cause serious disease when host defences are impaired but primary pathogens can cause disease even when there are not any immune defects. -Zoonotic
Give 3 examples of reservoirs
- Animals
- Environment
- Other humans
Are vectors always living?
No, non-living vectors are called Fomites e.g food, water, soil , utensils
What are examples of direct host-to-host transmission?
Airborne : aerosols which is coughing and sneezing )
Body contact such as kissing, touch , sexual intercourse
Define colonisation
What does the pathogen compete with the hosts flora?
-Establishment of a stable population of bacteria in the host
- nutrients and surface attachment sites
To overcome flushing mechanisms bacteria must do what?
Adhere to host cell surfaces or other surfaces e.g catheters
What are the stages of adherence of bacteria ?
-Association ( non-specific forces like charge)
-Adhesion using adhesins and host receptors
- Aggregation can occur to produce a biofilm - may disperse , new infection
-What are some example of bacterial adhesins?
-Give examples of host receptors
-Fimbriae and pili , capsules, flagella, lipoteichoic acids
-Blood group antigens, extracellular matrix proteins such as collagen
Invasins are an example of what ?
Virulence factors
What are the different roles of antibodies ?
- preventing attachment
- help phagocytosis , act as opsonins
-clump microbes
-neutralise toxins - attracts complement system
What are the different roles of antibodies ?
- preventing attachment
- help phagocytosis , act as opsonins
-clump microbes
-neutralise toxins - attracts complement system
What are toxins an example of?
Virulence factors
How can tissue damage occur?
1.Iron acquisition
2. Direct effects of bacterial toxins
3. Indirect effects of bacterial toxins
4. Induction of autoimmune responses
How do bacteria ensure that they have sufficient iron for growth?
Siderophores - bind iron with high affinity
Direct binding of iron transport proteins e.g transferrin
What do exotoxins act on?
Specific targets
What do endotoxins do?
Action is indirect , activates host systems that cause damage
Gram-positive bacteria only make ……toxins
Exotoxins are ……… and Endotoxins are Lipopolysaccharides
Exotoxins
Protein
Which type of toxins are heat stable ?
Endotoxins
Which toxins are more immunogenic ?
Which is more lethal?
-exotoxins
-exotoxins
How can humans be exposed to exotoxins?
- ingestion - e.g food
-colonisation of mucosal surface or tissue followed by toxin production - colonisation of wound followed by toxin production
What can endotoxins do when they activate host systems ?
-fever
-shock
-blood coagulation
-inflammation
Endotoxins are only produced by ……
Gram -ve bacteria
What are the 4 Eukaryote supergroups?
Excavata
SAR
Archaeplastida
Unikonta
What is responsible for organising the organelles?
The Cytoskeleton
What organelles are optional in protist cells?
Chloroplasts and the cell wall
What word sums up the collective group for eukaryotic photosynthetic organisms ?
What organelle is a green plastid?
Algae
Chloroplasts
Wha are photoautotrophic protists?
What are heterotrophic protists?
What are mixotrophic protists?
Photoautotrophic protists photosynthesise
They feed on bacteria, fungi and other (smaller) protists
They can do both
What is the difference in the flagella between projkaryotic and eukaryotic cells?
P- helical
E- 9:2 fibril arrangement
What is the way that we view/count protist cells?
Direct microscopic count
What are the cellular similarities between Protists and bacteria?
Both have cytoplasm, a cytoplasmic membrane and ribosomes
What method of reproduction do Protists use?
What type of division ?
Daughter cells are genetically similar but what differs between them?
Asexual
Mitosis
The number of organelles that they both have
What is the shape of the growth curve for Protists?
Same as for Bacteria
What do Protists produce that have similar adavantages to bacterial endospores?
What are some of these advantages?
-Cysts
- produced under unfavourable conditions, heats resistant, low water content , can survive long periods of time in the environment, antibiotic resistance, , effective dispersal mechanism
Which protists always have a cell wall?
What is it usually made from?
- non-motile photosynthetic protists
- all cysts
- cellulose
Protists without a cell wall need a mechanism to remove the excess water, what is it?
-a contractile vacuole
- involves a series of pore opening and closing depending on water content in vacuole
Protists without a cell wall need a mechanism to remove the excess water, what is it?
-a contractile vacuole
- involves a series of pore opening and closing depending on water content in vacuole
Why do marine species not need a contractile vacuole even though they have no cell wall?
The water potential / salt conc is the same as in the eukaryotic cells. No osmosis occur ( isotonic)
Where is the cut off for temperature and protist growth?
So which can’t grow? Why?
-60 degrees
-hyperthermophiles
- protists are eukaryotic cells, they have many membranes ( around organelles and cytoplasmic ) which can get denatured?
What are the 2 types of protists ( with regard to oxygen) ?
- Obligate aerobes ( need O2)
- Obligate anaerobes ( cannot grow in presence of 02)
In aerobic respiration in protists what is the start reactant?
Where?
Waste product?
O2
Mitochondria
CO2
In Anaerobic respiration what is the reactant?
Where?
Waste / Products?
-Pyruvate
- Hydrogenosomes
- H2, Acetate, CO2
In the endosymbiont theory, what did …….become?
- Alpha- proteobacterium
- Cyanobacteria
What did hydrogenosome evolve from?
- mitochondria
-chloroplasts - mitochondria
What is the evidence for the endosymbiotic theory?
- size of organelle = size of bacterium
- Phylogeny analysis relates their DNA to their bacterial origin?
- Have their own circular DNA and replicate by binary fission?
- contain same ribosomes as bacteria
-they have a double membrane (engulfing mechanism )
Selective digestion or no digestion can lead to ……..
Mixotrophy
Describe organellar mixotrophy ( selective digestion)
- Protist eats algal cells
- no digestion of plastids
- plastids fix CO2
-Plastids do not encode for polymerases - die and need replenishment
- more algal cells eaten
Described cellular mixotrophy in protists?
- Eats algal cells
-No digestion of algae
-Algae fix CO2 - Algae divide in cell
- Protist can live without the algae
What are constitutive mixotrophs ?
- Algae evolve into organelles
- Genetic transfer events
-Protist cannot live without the organelles
( only in flagellates )
Which type of protists carry out a) Organellar b) Cellular and C) Constitutive mixotrophy ?
- ciliates and amoebae
- ciliates and amoebae
- flagellates
How do flagellates move? Ciliates? Amoebae?
- flagella
- Cilia
- Cytoplasmic streaming
Are cilia orderly or random ? What does this help with?
Orderly
Helps with movement
What is the arrangement in motile cilia ?
9+2, dynein motor protein ( 9 pairs around and 2 single in centre )
What is the arrangement ( cross section ) in s non-motile cilium? Where are these in humans ?
9 + 0 ( no dynein motor protein) ?
“ Primary cilium” on all human cells , every cell has at least one attached to it
What method of feeding do ciliate Protozoa use ?
Filter feeding , the cilia direct the prey towards the mouth
Cytostome contains stiffer cilia
Sieve - correct sized prey enter food vacuoles
What are Vorticella ? How do they feed?
Bell shaped ciliate protists
“Mexican wave “ style movement of cilia , forms a vortex at the mouth, creating very large feeding currents
Suctorian ciliates are an exception , they have tentacles which all end in a ………..
They also have extrusomes which secrete ……….
They dissolve prey contents and suck out like a straw , we call this ………. Feeding
What word means many mouths ?
- cytostome
- toxins
- raptorial
- polystomy
How do mixotrophic ciliates acquire their photoautotrophic ability?
- Organellar mixotrophy and cellular mixotrophy
How can ciliates reproduce?
Asexually or sexual reproduction ( micronuclei swap)
What are the 2 stages of anaerobic respiration in the “sulphur ciliates” ? N
- pyruvate to hydrogen , acetate and co2 via hydrogenosomes
- methane produced via methanogenic bacteria
Which is the only type of protist which can feed by photoautotrophy, heterotrophs and mixotrophy ?
Flagellates
How do heterotrophic flagellates feed ?
- raptorial feeding
- filter feeding
There are ……… flagella and hispid flagella (little mini projections)
Naked
How does raptorial feeding with a hispid flagellum work?
Feeding currents due to flagella movement
Prey is drawn towards base of the flagellum
Ingested via cytoplasmic extensions
How does a flagellate with a naked flagellum increase its chance of prey capture?
- collar of tentacles ( microvilli)
-contractile actin
Describe choanoflagellates?
A group with a collar of tentacles , a single naked flagellum , attach to surface by means of a stalk
Dinoflagellates have a 2nd flagellum around where?
The waist
Which protists are most closely related to animals ?
Choanoflagellates
In shelled amoebae what is the shell also called?
What is the cytoplasm called inside the test ?
What is it called outside the test?
The test
Intrashellular cytoplasm
extracellular cytoplasm ( project it to move and or feed?
What are the 3 cell forms of naked amoebae?
Trophozoites - feeding form
Cysts - resting stage
Floating form - stiffened pseudopodia for dispersal
What are the 3 cell forms of naked amoebae?
Trophozoites - feeding form
Cysts - resting stage
Floating form - stiffened pseudopodia for dispersal
Where are testate amoebae found? How do they feed?
Freshwater, marine and terrestrial
Raptorial
Where are foraminiferans amoebae found ? ( the ones that look like metallic snails)
What feeding method?
Marine only
Diffusion
In diffusion feeding the stationary predator captures prey with sticky extrashellular cytoplasm what is teh cytoplasm extensions called?
Axopodia
Radiolarians and Heliozoans are both amoebae that have silica tests and use diffusion feeding what is the only difference ?
Radiolarians live in marine only environments but heliozoans live only in freshwater
What are the 3 groups within the “microbial loop”
- photoautotrophs
- bacteria
- heterotrophic protozoa
Protists have to maintain their cellular C:N:P ratio at
50:10:1
What is the problem with amoebae and macrophages being similar shape?
Bacteria practice evading digestion in amoebae by changing their antigens
What is the problem with amoebae and macrophages being similar shape?
Bacteria practice evading digestion in amoebae by changing their antigens
Why do protist diseases take a long time to treat?
Cysts are intermittently produced by the protists when antibiotics are used to kill the bacteria associated with the disease. ( can take 6 months to clear it)
What disease is caused by dirty contact lenses? What is the reservoir ? How is it transported ?
Keratitis
Water
Dirty contact lenses ( need hydrogen peroxide in teh cleaner for it to be effective)
What is the reservoir for PAM ( brain eating amoeba) ? How is it transmitted ?
- warm water
- warm water , the flagellate swims up the nose
What STD is a protist disease? Aerobic or Anaerobic? What does it infect ? Males or females are asymptomatic?
-Trichomoniais
-Anaerobic
- Infects urethra , vagina , prostate
- males ( lucky)
In the disease Leishmaniasis what is the reservoir and the vector? Is it aerobic or anaerobic ? Cysts or no cysts ?
- dogs
- sand fly
- aerobic
- no cysts
What type of protists form colonies? What colour plastids?
Synura , golden/brown
What type of protists form colonies? What colour plastids?
Synura , golden/brown
How can lab staff ensure that the results of their tests are reliable?
- internal quality assurance samples
-external quality assurance samples
What % of the values found in healthy volunteers are in the reference interval ? SO what % of the normal population will be outside the reference range?
-95%
-5%
What is a false positive ?
A result outside the reference range, but person is healthy and within the 5% excluded in the reference range.
What is a false negative?
- a patient has the disease but gives a “normal” result
What biological factors affect interpretation of biochemical result?
- different reference ranges for females and males
-diet - time of day
- stress/anxiety/ menstrual cycle can affect levels of hormones
- strenuous exercise- release of enzymes interfere with other tests
What is the range of analytes in point of care testing?
- glucose
-protein - cholesterol
- urea and creatinine
-hormones
-hCG
What are some problems often faced with biochemical specimens?
- difficult blood sampling —> haemolysis—— K+ release = pseudohyperlakaemia
-insufficient specimen - min vol required - errors in timing - 24h specimen
- incorrect specimen container
-inappropriate sampling site e.g downstream from an i.v. Drip
Incorrect specimen storage e,.g blood cells become l;easy and leak K+
What are the 3 main groups of fungi?
- zygomycota
- ascomycota
- basidiomycota
Are fungi eukaryotes/ prokaryotes?
What is the cell wall made from?
Is reproduction asexual or sexual?
What are they ( regarding carbon intake)
- eukaryotes
- chitin and polysaccharides
- both
- heterotrophs
What are the 3 types of heterotrophs that fungi can be ?
- saprophyte - derive nutrients from dead remains
- necrophytes - derive nutrients from organisms they have killed
- biotrophs - derive nutrients from living host
Which 2 of the heterotroph subtypes are classed as parasites?
- necrophytes , biotrophs
What are the differences between plants and fungi?
- plants are photoautotrophs but fungi secrete enzymes in order to digest and absorb organic material
What are the differences between plants and fungi?
- plants are photoautotrophs but fungi secrete enzymes in order to digest and absorb organic material
- fungi are usually more filamentous but plants are more box-like
- fungal cell walls are made from chitin and polysaccharides but plants cell walls are made from cellulose
- mitosis occurs in the nucleus in fungi but in other eukaryotes the nuclear envelope breaks down
When was the 5 kingdom classification created?
- 1969
In fungal yeasts:
- is it multi or single cell
-what shape ?
-Asexual or sexual
- can it form a colony ( name?)
-Size?
- single cell/ single nucleus
- oval or spherical
-asexual by producing identical daughter cell - yes ( pseudohyphae)
-3-5 micrometer diameter
In filamentous fungi ( molds) :
- single or multicellular?
- describe the filaments + give scientific word for it
- describe the tip growth of the filaments
-What word describes the mass of hyphae ?
Reproduce via…..
- multi
- long thread, like filaments- hyphae
- polarised tip growth
- mycelium
-spores
Dimorphic fungi can transition between …….. and ……. Under environmental cues such as …….
- yeast and filamentous forms
- temperature and co2
Describe asexual reproduction in a) yeast and b ) filamentous fungi?
A) buds a daughter cell
B) lightweight spores for effective dispersion
Colonise food supply rapidly
Haploid
Formed from aerial extensions from mycelia
Describe sexual reproduction in fungi ?
- union of nuclei to form diploid 2n state
- when nutrients are in poor supply usually
- more hardy , can survive adverse conditions
In sexual reproduction of fungi what is
A) heterothallism
B) homothallism
A) exchange of genetic material , 2 different mating types
B ) homothallism, some fungi can self fertilise and produce sexual spores
What word describes spores that
A) in a sack ( sporangiophore)
B) in a line
C ) fragmenting hyphae
- sporangiospores
- conidiospores
- athroconidia ( arthrospores)
What word describes spores that
A) in a sack ( sporangiophore)
B) in a line
C ) fragmenting hyphae
- sporangiospores
- conidiospores
- athroconidia ( arthrospores)
Describe the generalised overview of sexual reproduction in fungi
- haploid ( n)
- Dikaryon ( n + n )
Formation of a specialised structure - Dikaryon
Fusion of nuclei - diploid 2N
- germination of diploid sexual spore
- meiosis restores the haploid state to form haploid sexual spores
What are the 3 major divisions (phyla) of fungi?
- Zygomycota
- Ascomycota
- Basidomycota
Do zygomycetes have aseptate hyphae?
What is formed in its asexual reproduction ?
What about in its sexual reproduction form?
Yes
Haploid sporangiospores
Haploid zygospores
Describe the hyphae for ascomycetes?
What is formed in a) asexual reproduction and b) sexual?
Most are …………
- septate hyphae
- haploid conidospores
- haploid ascospores ( meiosis followed by mitosis )
- saprophytes
In Basidiomycetes are the hyphae aseptate or septate ?
Asexual or sexual
What type of spores?
What term describes the various types of fruiting body (e.g mushrooms ) ?
Septate
Sexual , asexual is uncommon
Haploid basidiospores
Basidiocarps
Why are basidiomycetes an issue for plants ?
They are saprophytes
What type of fungi are called fungi imperfecti and have an absent sexual reproduction cycle?
- Deuteromycetes
Are patients of true pathogens usually symptomatic or asymptomatic?
How many fungal species roughly are capable of causing systemic infection?
Do they display thermal dimorphism?
-asymptomatic
- 10
-yes
Describe thermal dimorphism
-There is an increase in temperature
-Yeast form (35-40 degrees)
-Reproduction via budding or endospores , parasitic
-Decrease in temperature
-Hyphal form < 30 degrees , reproduction via spores
Saprophytic
How many cases of Histoplasmosis ( common fungal disease) are there every year in the USA?
How many deaths are there?
-500,000
-less than 50 deaths
Describe the events in Histoplasma ( fungal ) infection in most cases and in some cases?
- soil containing bird dropppings in wind
- microconidia are inhaled
-patient develops mild pneumonitis - yeast phase develops and is phagocytosed, and multiplies by intracellular budding.
- In some cases phagocytes enter the blood and cause disseminated disease in a number of organs
What true fungal pathogen is most common in alkaline desert soils of Southwestern US?
< 35 degrees it is in its …….. form ?
At 37 degrees it is in its …….. form
Coccidioidomycosis
Filamentous ( arthrospores)
Spherules ( endospores in sporangia)
Describe the events in Coccidioides infection? ( fungal)
- digging in soil produces aerosol of arthrospores
- inhaled arthrospores establish a lung infection
- arthrospores develop into spherules that produce endospores which are released into the lungs
- compromised people can develop meningitis, osteomyelitis and skin granulomas
What is the difference in level of infection of immunocompromised and immunocompetent patients? The hyphal form of this dimorphic yeast is very…….
Immunocompromised- systemic organ failure
Immunocompetent : non- invasive local infection
Aggressive
What happens in Aspergillosis?
Spore germination in lungs “aspergilloma”
Tissue necrosis due to aggressive invasion using hyphae
Colonises lung / disseminates to brain/heart
What are Dermatophytes ? Give 3 examples
Superficial infections on healthy host
Ringworm and Athletes foot
What is the fungal equivalent of cholesterol? What do Azoles do ? What can Amphotericin B do if it attacks host cells?
-Ergosterol
- interrupt biosynthesis of ergosterol
- Induce liver and kidney failure
What does Fluorocytosine do ?
It’s a fungistatic that inhibits RNA synthesis, doesn’t kill fungus it stops growth instead
Describe pathogens of immature tissue ?
-broad host range
- soil borne pathogens attack roots
- aggressive invasion of root tips with extensive destruction and in water logged soils
Describe neurotrophic pathogens of mature tissue
Excrete toxins and cell wall digesting enzymes
Host cell death
Tissue invasion
Evoke host resistance mechanisms
Describe biotrophic pathogens?
- maintain host viability
- limited tissue invasion
- do not evoke resistance mechanism
- life cycle depends on living host
- arrive as spores on leaves
What ways of entering and infecting plant cells can haustorial biotroph fungi take?
- e.g Puccinia graminis goes via stomatal opening and infects mesophyll cells
E.g Erysiphe graminis infects directly through cuticle , epidermal layer
What is the problem of haustoria ?
They act as a nutrient sink diverting nutrients from growth and grain yield, compromised host and reduced photosynthesis
What is a virus?
A simple, miniscule, infectious, obligate intracellular parasite comprising of genetic material (DNA or RNA) surrounded by a protein coat (capsid) and/or an envelope derived from a host cell membrane
What are the 2 states that a virus can exist in ?
- virion (outside host cell for transmission )
-virus (inside host cell after infecting )
What is the term that describes teh period where there is no viral cell replication?
Eclipse period
What structure determines the shape of the virion ?
Capsomers
Describe the shape of a helical virus ? Polyhedral? Binal?
-capsomers bond together in a spiral fashion
-roughly spherical
-Irregular or complex structures
What are the functions of the capsid?
- protects the nucleic acid from enzyme digestion
-allows virion to penetrate host cell
-allows attachment
Where is the envelope usually acquired from in viruses?
-the host
What is a virophage ?
A virus that infects another virus
What is used by bacteriophages to attach and adhere to a bacterial cell?
-base plate
-tail fibres
What are the 6 stages of replication for a lytic bacteriophage?
-adsorption
-penetration
-replication
-maturation
-release
-reinfection
What happens in the adsorption stage of viral replication of bacteria?
What about penetration?
-attachment to specific receptors
-entry of DNA
What happens in the replication stage of the replication cycle of the lytic bacteriophage?
What happens in the maturation stage ?
Synthesis of viral nucleic acids and protein
Assembly and packaging of new virions
What are the alternative bacteriophages that are not lytic i.e they don’t kill the host? In temperate phages , the genome can integrate into the hosts chromosome what is this called? What does this produce?
-temperate phages or lysogenic phages
-a prophage
-a repressor protein which blocks lytic genes
How do we quantify bacteriophages?
Using molten agar containing bacteria and phages on a nutrient agar plate , the bacteriophages form plaques
What are some of the uses of phages in biomedicine?
- Listeria solution , on unprocessed foods e.g cheese
Meats and fish
-a bacteriophage enzyme (lysine gamma) kills Bacillus anthracis spores
-keep control of bacteria so are useful
Do swimming algae have a cell wall?
No
Which out of ciliates and flagellates has an only a macronucleus?
Flagellates
What are fungi used to control?
-insect pests
-phytopathogenic fungi ( effective in soil)
What are the mechanisms of control for fungi that control phytopathogenic fungi?
-parasitism of the pathogen by the BCA
-Production of antibiotics , BCA poisons the pathogen
-competition for nutrients, water and space
What are fungi called that parasitise other fungi?
Mycoparasites
What does Saccharomyces cerevisiae do in a high sugar environment ?
Ferments glucose into ethanol and carbon dioxide
What is Aspergillus oryzae used for? (Fungi)
Fermentation of soya beans
What fungi species is used in Quorn?
When was it developed? Approved for consumption?
Fusarium graminearum (venenatum)
1950s by Rank Hovis MacDougall
1980
What enzymes are produced commercially by Aspergillus niger?
-glucoamylases - liquid starch to high glucose syrup
-Pectinases - fruit juice
-Glucose oxidase - food preservation , diagnostic tests ( glucose + O2 ——> gluconate + h2O2 then 2nd test for colour change can diagnose glucose in urine)
What fungi is in penicillin ?
Penicillium notatum
What are some of the ways in which viruses wee named before a classification system was introduced in 1966/1971?
-geographical location e.g Ebola or Newcastle disease
-host organism they infect e.g African horse sickness virus, swine flu
-scientist who discovered them e.g Epstein-Barr disease
- specific type of disease e.g hepatitis a
-sites in the body e.g rhinovirus
What are the 2 systems for classifying viruses ?
-ICTV
-Baltimore
What are the 2 systems for classifying viruses ?
-ICTV
-Baltimore
What are the levels of classification by ICTV ?
-species
-genus
-family
-order
-class
-phylum
-kingdom
-realm
What must every virus do regardless of its genome?
Make mRNA that can be read by host ribosomes
What must every mRNa have?
A 5’ cap and a 3’ Poly A tail (adenine) - gene coding for protein is between these ends of the mRNA molecule
How many classes are there in the Baltimore system for viruses?
7
1.dsDNA
2.gapped dsDNA
3.ssDNA
4.dsRNA
5.+ssRNA
6.-ssRNa
7.+ssRNA with DNA intermediate
What are the possible ways that viruses can infect cells?
1)Transformation into tumor cells
1)Lysis (death of cell and release of virus) - most aggressive
3)Persistent infection (slow release + without cell death)
4)Latent infection ( present but no harm, later emerges in lytic infection) (requires a trigger)
What are the 6 stages of a virus life cycle ? And what 3 stages are they split into?
1.attachment
2.uncoating
(Entry)
3.replication
4. Biosynthesis
(Replication)
5.assembly
6. Budding
(Exit)
What are the exceptions that are viruses which do not require receptors to attach to host cells?
-fungal viruses and plants
Are these statements true or false?
-different viruses all bind to different receptors
-viruses of the same family may bind to different receptors
-viruses only bind to one receptor
-false
-true
-false
Are these statements true or false?
-different viruses all bind to different receptors
-viruses of the same family may bind to different receptors
-viruses only bind to one receptor
-false
-true
-false
What are the 3 possible mechanisms for how viruses enter cells ?
-injection of nucleic acid (Polio)
-fusion of envelope with host membrane (measles)
-Endocytosis ( herpes)
What are the 3 possible mechanisms for how viruses enter cells ?
-injection of nucleic acid (Polio)
-fusion of envelope with host membrane (measles)
-Endocytosis ( herpes)
What is synthesised during replication of viruses?
-viral proteins (mRNA so unanimous)
-viral genome (virus-dependent)
What is the typical infection cycle for fungi in insect pest control?
1) spore attachment
2) germination to intersegmental region
3)penetration of cuticle (enzymes e.g proteases and lipases)
4) hyphal invasion beneath cuticle
5) sporulates
6) proliferation in to blood (yeast phase)
7) death (toxins)
8) saprophytic stage- spores
What fungi is often used in pest control? Why is good for economical reasons ?
Verticillium lecanii
It produces spores in liquid fermentors
Why is Acrylaway which is purified from Aspergillus Niger fungal cultures beneficial for eliminating inc cancer risks?
It prevents acrylamide production which is a a carcinogen produced when starchy foods are cooked at high temperatures
What are statins ?
Fungal metabolites that inhibit the biosynthesis of cholesterol and are used to reduce plasma cholesterol levels
Name some older viral diseases
Polio, hepatitis , influenza , warts , common colds, rabies, measles ,mumps , rubella ,leukaemia
What are some examples of re-emerging /old diseases?
West Nile fever, Ebola, aids, SARS-cov-2 , monkeypox , avian flu
What type of virus is Rabies?
Rhabdovirus
-SsRNA-group 5
What are some rabies hosts? Where does the virus enter? Where does it move to?
What does it cause?
Cats,dogs,horses, wolves, bats , bears etc
Peripheral nervous system
Central nervous system
Swelling of brain (encephalitis) - death
What are the 2 forms of Rabies?
Furious and dumb
Furious -
80-90%
Change in behaviour and voice
Paralytic stage
Death
Dumb-
10-20%
Paralytic
Sleepiness
Death in 3 days
When was Monkeypox first exported in humans?
1970, Africa
How can monkeypox be transmitted?
-Animal-human via bites
And scratches from infected animals
bushmeat
-Human-human
Direct skin-skin contact with lesions on skin
Indirect contact with contaminated fomites such as bedding or clothing
What is the initial stage of monkey pox signs ?
Discolouration - not infectious until this point
What vaccine is available to specific people for monkeypox ?
MVA 9 modified vaccinia Ankara
What are viriods?
Features?
Smallest known pathogen
Infectious agents that resemble viruses
Small, circular
No capsid
Resistant to proteases and nucleases
Only infect plants
Don’t encode for proteins
What are obelisks ? Features?
Viriod like elements that are first identified in human oral and stool metatranscriptomic data
circular RNA genome
Rod-like secondary structures
Open reading frames coding for a novel protein superfamily
Distinct phylogenetic group, no structural similarity to known biological agents
What are prions ?
Small proteinaceous infectious particles which resist inactivation and contain no genetic material
Causes folding of proteins which causes illness
Accumulation of misfolded protein scrapie prion protein
What is the mutation pathway that leads to prion disease?
Glycoprotein PrPc usually exists in healthy animals
Interaction between PrPC and PrPSC ( which was generated either spontaneously, from mutant PrPc or inoculation of PrPSC)
Conversion to PrPSC which changes protein folding pattern
Accumulation of aggregated PrPSC
What is scrapie ?
Signs?
Any treatment ?
Degenerative , fatal disease of the CNS of sheep and goats
Ataxia (coordination , movement , speech effects) , recumbency (leaning, resting, reclining )
No
What is BSE?
What are the 3 presentations ?
Which form can be transmitted to humans ?
Bovine spongiform encephalopathy (mad cow disease)
Classical BSE
H-type atypical BSE
L-type atypical BSE
Classical - this causes the human variant Creutzfeldt-Jakob disease
What human diseases are caused by prions?
Kuru - trembling
Fore tribe of Papua New Guinea via funerary cannibalism ( eating family members brain)
CJD- Creutzfeld-Jacob disease
- lose ability to think and move, always fatal
What human diseases are caused by prions?
Kuru - trembling
Fore tribe of Papua New Guinea via funerary cannibalism ( eating family members brain)
CJD- Creutzfeld-Jacob disease
- lose ability to think and move, always fatal
Are the 4 methods of spreading CJD?
Sporadic sCJD
Familial/ inherited fCJD - Rare
Variant CJD (vCJD) - meat from BSE cow
Latrogenic CJD (iCJD) - accidentally spread through medical or surgical treatment
What are 2 examples of solitary amoebas cells?
Chlamydomonas and Mallomonas
