post lecture notes Flashcards
who was the god father of microbiology?
Anton van Leeuwenhoek
what were Anton van Leeuwenhoek’s first observations made on?
hand-crafted microscopes using plaques scraped from his teeth
what are animalcules?
what Anton van Leeuwenhoek called the first single celled organism
what are the 3 types of images we see on a microscope?
bright-field
phase contrast
dark-field
how does glow in the dark work?
absorbs 1 wave length, emits another
what’s the process of TEM sampling preparation?
- fixation
- staining
- dehydration
- polymerized
- sectioning
how does cry-term work?
- sample: apply to EM grid
- blot: remove liquid
- plunge freeze: liquid ethane
how does going from 2D to 3D work?
- specimen rotates in the beam
- combine and compute 3D transform
- reconstruct object in 3D
(using electron microscope)
what does microscopy reveal?
the vast realm of organisms invisible to the unaided eye
what do fluorescent microscopes show?
how parts function within a living cell
what do electron microscopes show?
cell’s interior; how all the parts fit together
describe light microscopy
resolves images of individual bacteria by their absorption of light
what is brightfield microscopy?
specimen is a dark object against alight background
describe electron microscopy (EM)
uses beams of electrons to resolve details smaller than light microscope
describe scanning electron microscopy (SEM)
electron beam is scattered from the metal-coated surface of an object, generating an appearance of 3D depth
describe transmission electron microscopy (TEM)
the electron beam travels through the object where the electrons are absorbed by an electron-dense meal stain
what can H. pylori cause?
gastric cancer
true or false:
all H. pylori is bad?
false
what is a facultative anaerobe?
aerobic but can survive in anaerobic conditions
how many cells in the average bowel movement?
10 trillion
How do Cyanobacteria spp. inside rock photosynthesiz?
in quartz, translucent, some light can get through
can archaea’s have viruses?
yes, even more complex than bacteriophages
what are some barriers we have to manage our microbes
skin
mucous membranes
blood brain barrier
what is the immune system?
A complex system of organs, tissues, cells and cell products that work in concert to recognize and neutralize potentially pathogenic threats
what happens when human barriers are breached within the body
the immune system comes into play
what are the 2 arms of the immune system?
innate and adaptive
what does the innate immune system include?
- Physical barriers
- Chemical and cellular responses (come into play if barriers are breached)
true or false:
Contact with an infectious agent guarantees that a person will get sick
false
what does a pathogen need to cause disease?
- Breach host defenses
- Survive innate defense mechanisms
- Begin to multiply
why is the skin a good barrier?
Difficult to penetrate by microbes when intact (keratin)
why is the mucous membrane a good barrier?
- 200-300 m2 in the average human!
- Epithelial cells are tightly connected to support a strong barrier function
- Selectively. permeable to allow absorption of nutrients
why are the lungs a good barrier?
- Have a ‘mucociliatory escalator’
- Microbes larger than ~100μm are trapped by hairs in the nose and by cilia lining the upper airways
- Trigger sneezing, to forcefully remove foreign material, including microbes, from the respiratory tract
what are all physical barriers tightly connected to?
lymphoid tissues
which of the following is least likely to influence susceptibility to infection with a given food-borne disease:
a) infectious dose
b) virulence potential of the pathogen
c) previous appendectomy
d) host genetics
e) recent history of antibiotic use
c) previous appendectomy
how did the complement system get its name?
- Complement is a set of proteins made by the liver
- Named in 1890s because they complement antibodies in the killing of bacteria
where do the complement proteins circulate?
- in blood and enter tissues all over the body
- Circulate as inactive forms and are proteolytically cleaved to make them active
- complement activation
what is the name of the complement components/complexes?
C1-C9
how many soluble and membrane bound protein components of the complement system are there?
~30
what are the 3 complement activation pathways?
- The classical pathway
- The lectin pathway
- The alternative pathway
where do all 3 complement pathways converge?
lytic pathways
what does protein shape determine?
what they can and cannot do
describe the gut concentration gradient of defensins
- Higher in close proximity to the crypts of the epithelium
- Secretion is from the crypts
- Keeps out even the normal microbiota
What sort of cells are found within blood?
- Red blood cells
- White blood cells
- Platelets
which kind of blood cells are part of the immune system?
white blood cells
what do white blood cells include?
- polymorphonuclear leukocytes (PMNs, granulocytes or polys)
- Monocytes & macrophages
- Dendritic cells
- Mast cells
how many blood cells does 1 literals of human blood contain?`
~6 billion
what does Myeloid bone marrow stem cells differentiate into?
phagocyte cells
what does phagocyte mean?
a cell that eats
wha are NETs
Neutrophil Extracellular Trap
what is NETosis?
An unusual form of cell death by the neutrophil
what do neutrophils do when they sense an invader?
- spews a latticework of chromatin and antimicrobial compounds into the vicinity
- Prevents spread of the pathogen
- Allows rapid phagocytosis
what is inappropriate NETosis thought to underlie?
autoimmune disease called systemic lupus erythematosus (lupus)
what do monocytes differentiate into?
macrophages
where do monocytes circulate?
the blood stream
describe movement of monocytes?
- attracted by chemical signals (cytokines) to sites where they are needed
- As they travel through the blood vessels (extravasation) they differentiate into macrophage
true or false:
Monocytes are large structures that can ingest many microbes at one time
true
what do dendrocytes posses?
long protrusions that can squeeze through tight spaces to sample microbes
what do Cytokines, chemokines and interferons act as?
- language of our immune system
- Close-range acting ‘hormone’ system
- particularly effective at signalling ‘danger
what are some cytokines important for?
- anti-inflammatory signals after danger has passed
- Reset the homeostasis
what are Macrophages and dendrocyte also?
antigen presenting cells (APCs)
what do Macrophages and dendrocyte do when they ingest antigens?
process them and display them on their surfaces for T-cells
what is the link between innate and adaptive immune systems?
Macrophages and dendrocyte
what are Peyer’s patches?
Specialist sites within the small intestine
how do macrophages recognize microbial cells?
- Have non-specific receptors on their surfaces
- But they also rely on circulating helper molecules
why are any pathogens encapsulated?
to help them evade the innate immune system
how are pathogens recognized by the immune system?
- Cells of the innate immune system have specialized sets of receptors to recognize invariant and essential microbial factors that are unique to the microbe
- These are referred to as Pattern Recognition Receptors (PRRs)
what do PPRs recognize?
MAMPs -Microbe Associated Molecular Patterns
what are Toll-like receptors?
transmembrane receptors on some immune cells that recognize viral and bacterial products
what are TLRs useful for sensing?
external MAMPs
what do NOD-like receptors do?
- bind MAMPs and Activate cytokine production
- Form a complex called an inflammasome that triggers apoptosis
where are TLRs found?
outside the cell
where are NLDs found?
inside the cell
describe natural killer cells
- Not phagocytic
- A lymphocytic cell, distinct from T cells and B cells
- Large and granular
- Make up ~2% of lymphocytes in the body
- Thought to be a halfway house between innate and acquired immunity
- Don’t attack pathogens themselves, but instead attack host cells that have become overwhelmed by pathogens
true or false:
Most aspects of the innate immune response have a direct connection to the adaptive immune response
true
which branch of the immune system has memory?
adaptive immune system
what are the 2 types of immune memory?
humoral immunity
cell-mediated immunity
describe humoral immunity
- Antibodies directly target microbial invaders (B-cell response)
- Target infections in the body’s fluids (humors)
describe cell-mediated immunity
- teams of T-cells (T-lymphocytes) work together to recognize antigens displayed on infected cells
- Target infections in the body’s cells
true or false:
humoral and cell-mediated immunity are intertwined
true
true or false:
you are born with adaptive immunity
false:
develops as the need arises
what happens if the adaptive immune system is missing?
Usually a lethal mutation… SCID
how long does it take for the adaptive immunity to develop?
over ~3-4 day period following exposure to an invading microbe
what does the immune system recognize?
small pieces of a given antigen, called antigenic determinants or epitopes
what does phagocytosis produce?
many epitopes for the adaptive immune system
what does each B-cell recognize?
one specific epitope
what does the response to an infection involve?
thousands of different B-cells, each of which recognizes a particular epitope
what stimulate B-cells (B-lymphocytes) to differentiate into antibody producing cells?
Antigens (from ‘antibody generators’)
when does humoral response start?
when an antigen triggers the differentiation of B-cells into antibody-producing factorie
when does cell mediated response start?
when certain T-cells become activated by microbial antigens that are presented to them
what do activated T-cells do?
- can directly kill an infected host cell
- Also produce cytokines that initiate a macrophage feeding frenzy at the site of infection
which lives longer: plasma cells or memory B cells?
memory B cells: decades vs. plasma cells 4-5 days
what can the adaptive immune system recognize?
immunogenicity
what is immunogenicity
The effectiveness by which an antigen elicits an immune response
where is an antigen placed?
on a major histocompatibility complex (MHC) protein
true or false:
Binding of antigen to MHC needs to be strongfor T-cell to recognize it properly
true
what do T-cell receptors bind?
antigen and MHC Together with accessory molecule
what do mature T-cells differentiate into?
- T-helper (TH) cells/ CD4+ cells
- Cytotoxic T-cells (TC)/CD8+ cells
what do TH cells do?
- Associate with MHC class II proteins on APCs
- trained to memorize databanks of antigens and to alert B-cells if circulating antigen is detected
- determine which cytokines will allow the immune system to be most useful for the host during infection
what do TC cells do?
- associate with MHC Class I proteins on APCs
- trained to seek and destroy cells presenting noxious antigens on MHCI (indicating they may be infected)
where do B cells mature?
bone marrow
where do T cells mature?
Thymus
what are the 2 types of that TH cells differentiated into?
TH1 and TH2
what is TH1 most active against?
intracellular bacteria and protozoa
what is TH2 most active against?
helminthic infections
why do proteins generally make for the best types of antigens compared to carbohydrates, nucleic acids and lipids?
proteins have a greater differentiation of shape than carbohydrates, nucleic acids or lipids
true or false:
As well as effector T-cells, some TH cells differentiate into memory TH cells
true
what do regulatory T-cells do?
do not promote an immune response but help to restore homeostasis after infection
what is the lack of Treg cells associated with?
chronic inflammation
where do all T-cells pass through to get exposed to self antigens?
thymus
how many T-cells survive the passing through the thymus?
2%
How do we learn to live with the antigens of our own bodies/the foreign antigens of our microbiota?
antigen does is important
why is antigen does important?
- If antigen dose is over a threshold value, then B-and T-cells become over-stimulated
- T-cells become non-functional
- B-cells do not respond to subsequent antigen exposures to make antibodies
what are vaccinations used for?
killed, attenuated or engineered antigen sources to induce an immune response without causing disease
why is immunological specificity important in vaccinations?
An antibody made to one epitope will not bind to another epitope (unless that epitope is very similar)
what is the key to immunological specificity?
Antibodies (immunoglobulins)
what does the typical antibody look like?
antibody: 4 polypeptide chains
•2 large heavy chains
•2 smaller light chains
- Bound together by disulfide bonds
what is anergy?
absence of the normal immune response to a particular antigen or allergen
what are the 5 heavy chain types?
α, μ, γ, δ, ε
what are the 2 light chain types?
κ, λ
what does α =?
IgA
what does μ =?
IgM
what does γ =?
IgG
what does δ =?
IgD
what does ε =?
IgE
what is an isotope?
define the various heavy chains of a species
what is an allotype?
differences in the constant region shared by some but not all members of a species
what is an idiotype?
differences in the hypervariable region within an individual
describe IgG
- Simplest, smallest and most abundant antibody in blood and tissue fluids
- A monomer, with 4 classes (IgG1-4)
- Each class varies in aa sequence and interchain cross-linking
what are the jobs of IgG?
- Binds and opsonizes microbes (allowing phagocytes to grab them more easily)
- Binds and neutralizes viruses
- Activates the classical complement pathway
describe IgA
- Major secreted antibody of mucosal surfaces
- Most commonly found as a dimer, linked by disulfide bonds to the J (joining)-chain protein
- Secretory piece is wrapped around both molecules during secretion
- “secretory IgA” is found in tears, breast milk and on mucosal surface
describe IgM
- Can be found as monomers on the surface of B-cells
- But is most commonly found as a pentamer held together by J-protein
- First antibody isotype detected during the course of an infection
describe IgD
- Present in trace amounts in the blood
- Exists in monomeric form on surface of B-cells
- Plays a role in B-cell activation
- Function not well understood
•Does not bind complement
•May play a role in allergy as well as activation of the immune response to respiratory pathogen
describe IgE
- Present in trace amounts in the blood
- Found more prominently on the surfaces of mast cells and basophils
- These cells are loaded with inflammatory mediators (held in granules)
- When 2 mast cells or basophils are cross-linked by antigen via IgE, mast cells degranulate and act to quickly amplify the immune response
- Unfortunate side-effect in some people: anaphylaxis
what are the types of vaccines?
- Live attenuated
- Inactivated
- Subunit
- Toxoid
- Conjugate
why does some vaccines such as tetanus not benefit from heard immunity?
not passed foreperson to person, only from source
true or false:
Normally, B cells that escape from the negative selection process cannot be activated because they require a cognate THcell
true
why is it important to treat stream throat?
- makes a protein called ‘M protein’
- Parts of this protein very similar to a cardiac protein
- The cardiac-like epitope may be encountered by an ‘escaped’ self-reacting B cell
- The cognate T cell may recognize flanking non-self proteins and activate the B cell
- The B cell responds –makes plasma cells that secrete antibodies to the cardiac protein
- Damage to host cardiac tissue occurs
- Rheumatic fever –can lead to scarring of heart valve
what is the influenza virus?
a negative strand RNA virus
what are the 3 types of influenza?
- influenza A
- influenza B
- influenza C
describe influenza A
- one of the most common life-threatening viruses of the western world
~ 10% of the population of US and Canada are infected every year
~36000 deaths annually in the USA - Pregnant women and the elderly are most susceptible
describe influenza B
- Narrower host range than influenza A
- Can cause serious disease but mutates much more slowly
describe influenza C
- Narrower host range than influenza A
- Can cause serious disease but does not spread as easily
what are the main influenza pandemics from history?
- 1918: “Spanish ‘flu”
•Infected 20% of the world’s population, originated from a bird-infecting strain - 1958: “Asian ‘flu”
- 1968: “Hong Kong ‘flu”
- 2009: fear that new H1N1 variant would cause the next pandemic
•“swine ‘flu”
•Turned out to be extremely infectious, but caused relatively mild disease
what is the newest fear involving influenza?
- H7N9 –causes very serious disease in a high proportion of infected people
- However, as of yet, is not transmissible person-person (only bird-person)
- Big fear –virus will mutate and become transmissible
- A future strain may have the seriousness of H7N9 and the transmissibility of H1N1, and that would be very bad indeed
describe the virion structure
- No geometrical capsid
- Instead a shell of matrix proteins (M1) that surround the 8 RNA chromosome fragments
- Matrix is surrounded by a membrane envelope
- Derived from the host cell during budding
- Viral envelope proteins hemagglutinin(HA) and neuraminidase (NA) stud the surface of the virus
how many negative sense RNA segments does the virion genome have?
8:
- Each is coated with nucleocapsid proteins (NPs)
- Each encodes 1 protein
- 2 segments undergo splicing to encode 2 further proteins
why does Each segment is packaged with an RNA-dependent RNA polymerase complex?
- During viral assembly in an infected cell, segments are packaged precisely
•They link to each other in order as they arrange themselves
•Each segment lines up like a bundle of sticks
•Tiny molecular extensions seem to connect these sticks
how many virions can each host cell produce?
10,000
what does the H part in influenza stand for?
hemagglutinin
how many HA subtypes are there for influenza?
18
what does the hemagglutinin form with an N-terminal fusion peptide?
a trimer complex
describe what the H bit of influenza does
1) HA C-terminal domain recognizes and binds to host cell sialic acid receptor
2) Triggers uptake of virion by endocytosis
3) Endocytic vesicle acidifies and produces a conformational change that exposes the N-terminal fusion peptide
4) Fusion of host and viral membranes can now take place
5) Triggers release of the genome cargo into the host cytosol
what is the natural reservoir for influenza A virus?
birds
what determines if other animals are susceptible for influenza A virus?
- the presence of a host cellular protease to cleave the hemagglutinin (HA) and initiate infection
- nature of the cell-surface glycoproteins on host cells that bind the HA and allow endocytosis
describe H7N9
- The major contributor to this strain’s emergence is thought to be the mixing in close proximity of very large numbers of wild and domestic birds in food markets in China
- does not easily spread from person to person, but it causes very high mortality in humans
- approximately 1 out of 3 persons infected will die
what is the pathway of the influenza virus once infected?
1) Viral segments travel to nucleus and enter nuclear pores
2) Attached viral RNA polymerase synthesizes (+) strand RNA (used as mRNA or as templates for generating progeny (-)RNA)
3) mRNA travels to cytoplasm for translation to viral proteins –these are processed by the ER/Golgi & sent to the host cell membrane
what does the N bit of influenza do?
- Envelope proteins and viral genome packages travel to cell membrane for packaging into new virions
- Within the cell membrane, envelope proteins assemble around the genome and matrix proteins
- Virion then buds out of the host cell
- Neuraminidase cuts the virion loose from host glycoproteins to release it to the extracellular space
how many neuraminidase ‘N’ variant are there?
11
what is drifting regarding influenza?
- The ability of influenza virus (A and B) to mutate and change slightly
- Usually because of RNA replication errors in HA and NA genes
what is shifting regarding influenza?
- A big change in the structure of the ‘flu virus
- Can be caused by jumping of the virus into a new species
- Can be caused by reassortment of the genes from 2 different viruses mixing in a single host (usually a pig)
what is a retrovirus?
- a major class of RNA viruses
- Reverse the normal order of synthesis to copy their RNA into a ds-DNA
- Integrated into the host genome
what group is HIV in?
- lentivirus group of retroviruses
- Cause infections that progress over many years (‘lenti’= slow)
- Most famous is Acquired ImmunoDeficiency Syndrome (AIDS)
who discovered HIV?
French virologist Luc Montagnier and American virologist Robert Gallo
how long does it take to produce enough flu vaccine?
~6 months`
what did HIV evolve from?
viruses infecting African monkeys
when was the first case of AIDs in the USA reported?
1981
how many people are newly infected with HIV every year?
1.7 million
how many people globally were living with HIV by the end of 2018?
37.9 million
why is there no cure for AIDs yet?
- Retroviruses have a high mutation rate because of the high error rate of the reverse transcriptase enzyme
- Even within a single patient, the virus evolves into many different ‘quasispecies
- The replication of HIV is very complex
- Large number of regulator proteins that allow the virus to hide effectively within host cells
Structure and genome of HIV
- envelope comes from host cell membrane
- electron dense core
- Unlike influenza, each RNA strand contains a complete ‘map’ of HIV genes
- The 2 RNA genomes can have different mutations arising from distinct replication events, thus the HIV genome can be considered to be ‘diploid’
what does gag code for?
capsid, matrix protein
what does pol code for?
reverse transcriptase, integrase, protease
what does env code for?
envelope protein
what is the primary receptor for HIV?
CD4 surface protein on T-lymphocytes
what is the HIV viral binding partner?
- Envelope spike protein –gp120 –
- (SU and TM regions)
- SU binds, TM unfolds, extends fusion protein into host membrane
- Host and viral membranes fuse
what must retroviruses do in order to generate progeny virions?
integrate their genomes into the host cell genome
describe the replicative cycle
- RNA genome needs to serve as a template for DNA complement
- Then RNA template needs to be replaced with DNA to give ds DNA for integration
- Reverse transcriptase accomplishes all of this
true or false:
HIV has an exceptionally large number of accessory proteins
true
what do the large number of accessory proteins in HIV given?
the level of virus production and the duration of the quiescent phase
when does AIDS develop?
when CD4+ T-cell counts are <300 per mm3
what is the main symptom of AIDS?
susceptibility to infections that are unusual in the healthy population
what might some potential anti-HIV drugs do?
- Block attachment to host cell
- Prevent fusion of viral and host membranes
- Inhibit reverse transcriptase
- Inhibit integrase
- Inhibit HIV protease
true or false:
HIV can survive outside the human body for long
false
what is Shiga toxin?
- Originally comes from a bacteriophage
- One of the most potent bacterial toxins known
- Acts to inhibit protein synthesis within target cells
- A ribotoxin
- Kidney cells are particularly sensitive to intoxication•2 subunits to this exotoxin: A and B (AB5)
why does E.coliO157:H not cause disease in cattle?
receptor toxin is absent
how does retrograding trafficking work?
- Stxbinds to Gb3 receptors on host cells
- Next is taken up by the host cell into an endosome
- Next is trafficked to the Golgi
- Then to the ER, where the active part of the toxin is separated from the binding part
- The active subunit enters the cytosol and injures ribosomes, so that protein synthesis is halted
describe V. cholerae
- proteobacteria member, related to E.coli
- Flagellated, highly motile bacterial cell (1 polar flagella), very short generation time
- Lives in salt and fresh water, concentrates in shellfish and plankton
- Over 150 identified serotypes based on O-antigen
which 2 strands of V. cholerae are toxigenic?
O1 and O139
how many world pandemics involving cholera have there been?
7
what are the symptoms of cholera?
- begin out of the blue with sudden onset of explosive, watery diarrhea
- Painful abdominal cramping soon starts
- Diarrhea continues
~ 20 litres of fluid may be lost per day
•Rice-water stools
•Te e m i n g w i t h b a c t e r I a - Without fluid/electrolyte replacement, death soon occurs
- With treatment, disease is self-limiting
what is cholera toxin?
- A-B type toxin, AB5similar to Stx
•1 A subunit (active)
•5 B subunits (binding) - ADP-ribosylating toxin
- Subunits are assembled in the periplasm and secreted via pseudopilins into the extracellular space
- Mechanism analagous to a piston
- Whole CTX (5xB subunits plus 1xA subunit) is secrete
describe e. coli
- Gram negative, facultative anaerobe
- Most strains are motile using flagella
what phylum are e. Colin?
Proteobacteria
what family are E. coli in?
Enterobacteriacea
how many antigenic types of E. coli are there?
over 700
what is EHEC?
- Primarily a disease of the developed world
- not a common infection, but very serious and sometimes fatal
- Extremely low infectious dose
- Zoonotic, mainly carried asymptomatically in ruminants (esp. cattle)
- Can contaminate water supplies and vegetable crops
- Virulence determinants: pedestal formation, and production of Shiga toxin
what is a type 3 secretion systems?
- Molecular syringe
- Related to flagellar apparatus
- For secretion of protein effectors directly into the host cell (as well as into the extracellular milieu
- Used by several important pathogens including Salmonella enterica, Shigella, Yersinia
what is secretion?
a highly organized complex of many proteins
what is the T3SS or EHEC used for?
inject a very peculiar ‘effector’ into host cells (Translocated Intimin Receptor)
what are effectors?
the mediators for communication between host and bacterium
what is the e Gs alpha subunit (Gαs) protein involved in?
in hydrolyzing GTP to GDP + Pi
what does the A1 subunit fragment catalyze?
ADP-ribosylation of the Gs alpha subunit (Gαs)
what does longer activation than normal of (Gαs) lead to?
- increased adenylate cyclase activity
•Which leads to an increased intracellular concentration of cAMP
•Which over-activates protein kinase A
•Which phosphorylates the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel proteins
•Which leads to ATP-driven efflux of chloride ions from the cell to the intestinal lumen
what does accessory cholera toxin do?
fluid accumulation
what does Zonnula occludens toxins do?
disturbed tight junction integrity
what is the vaccine for cholera?
- Dukoral is the best-known
- Both killed, whole V. cholerae cells as well as recombinant CTX-B subunit
- Given with a bicarbonate buffer
- Stimulates both antibacterial and antitoxin antibodies
how many subunits does the AB toxin have and what are they?
2 subunits –one for binding/internalization, one for toxic activity
what famous AB toxins are there?
- Bacillus anthracis toxins
- Corynebacterium diphtheriae toxin
- Some Clostridium perfringens toxins
- Tetanus toxin
- Botulinum toxin
what used to be a major risk of death before vaccines and antibiotics?
tooth decay
what is sterilization?
The process by which all living cells, spores and viruses are destroyed on an object
what is disinfection
the killing or removal of disease-producing organisms from inanimate surfaces
what is antisepsis?
Removing pathogens from the surface of living
what is sanitation
Reduction of the microbial population to safe levels
how is efficiency of an antimicrobial measured?
decimal reduction time (D-value)
- length of time it takes and agent of condition to kill 90% of the population
what is the efficiency of an antimicrobial influenced by?
initial population size, concentration of antimicrobial agent, duration of exposure
what are the physical agents that kill microbes?
- high temperature and pressure
- pasteurization
- cold temperatures
- filtration
- irradiation
what kind of heat is a more effective killing agent: dry or moist?
moist
what does an autoclave do?
combines moist heat (steam) with high pressure to effectively kill even endospores
who originally devised pasteurization?
Louis Pasteur
what is pasteurization?
Involves heating a food to a specific temperature for a short time to kill Coxiellaburnetii
true or false:
most pathogens grow poorly at temperatures <4-8C
true
which food pathogen can grow in cold temperatures?
Listeria monocytogenes
what do you do is your solution is sensitive to heat?
flitration
what is irradiation?
Bombardment of food with high energy electromagnetic radiation
what do commercial disinfectants do?
Cause damage to proteins, lipids and DNA
tru or false:
copper ions are antimicrobial
true
what binds to disinfectants, slowing penetration into the biofilm?
Extracellular matrix proteins and polysaccharides
what is an antibiotic?
A compound that kills or inhibits the growth of microorganisms
who helped with the discovery of antibiotics?
- Duchesne, 1896
- Fleming, 1928
- Florey, Chain ~194
true or false:
antibiotics are mainly natural products
true
what are the main properties of antibiotics?
- Selective toxicity
- Broad vs. Narrow spectrum
what is bactericidal antibiotics?
Kills the target bacteria
what is bacteriostatic antibiotics?
inhibits growth, immune system clears the infection
what is minimum inhibitory concentration?
the lowest concentration of the antibiotic that will prevent the growth of the organism
what are the classical targets of antibiotics?
- Cell wall synthesis
- Peptidoglycan
- Cell membrane
- Nucleic acid synthesis
- DNA synthesis
- RNA synthesis
- Protein synthesis
- Metabolism
for the most part, what is penicillin more affective against: gram negative or gram positive?
gram positive
what does gyrase do?
Gyrase functions to relieve the strain on the DNA as it is being unwound by helicase during replication
what is resistance?
The ability of microorganisms to resist the effects of antimicrobial agents (one or more) that they were originally sensitive to
why does resistance happen?
Antibiotics have been overused and misuse
what is intrinsic resistance?
resistance of a bacterium to an antibiotic that is conferred by the normal physical attributes of the cell
how can resistance occur?
DNA mutations
•Acquiring new genes through horizontal gene transfer
•Conjugation, transformation and transduction
what are the 4 mechanisms of antibiotic resistance?
- alter the target
- destroy the antibiotic
- modify the antibiotic
- pump antibiotics out of the cell
how does altering the target work?
modifying the target so it no longer binds to or is recognized by the antibiotic
what is biocontrol?
A method of introducing an agent organism into a new ecosystem to naturally prey on and suppress target “pest” organisms
what is an agent?
The newly introduced species -Predator
what is a target?
The defined “pest,” whose population is suppressed by the agent -Prey
true or false:
biocontrol eradicates a target species
false:
decreases, does not eradicate
what is myxoma virus and how does it work?
- Enveloped virions
•Brick-shaped with a bio-concave core
•Non-segmented, linear ds DNA genome
•During lifecycle produces proteins that interfere with host immune system
what is myxomatosis?
- Lumps (myxomata) and puffiness appear around the head and genital area
- Progresses to acute conjunctivitis
- Loss of appetite, fever, listlessness
- Death within 14 days, usually less than 48hr
true or false:
The more specific the agent, the more controlled the intervention and fewer unintended consequences arise
true
what are the 3 kinds of biological control?
- Classical biological control
- Conservation biological control
- Augmentation biological control
what is classical biological control?
- Control of pests introduced from another region through importing specialized enemies of the pest from their native range
- Aim: to establish a sustained population of the new enemies
what is conservation biological control?
- Manipulation of the environment to favor natural enemies of the pest
what is argumentation biological control?
- number of biological control agents is supplemented
- Commonly used when biocontrol agent cannot adapt and survive long-term in the new environment
what is inoculation?
introduction of a small number of individuals of the biological control agent
what is inundation?
introduction of vast numbers of individuals
true or false:
Most pollutants can be broken down or detoxified by microbes under ideal conditions
true
how do you get gut dysbiosis?
reduced microbiota diversity + poor lifestyle choices + poor diet
what are probiotics?
live organisms that, when administered in adequate amounts, confer health benefits on the host
what are prebiotics?
- ‘Food’ for your gut microbes
•Typically non-digestible fibre compounds
true or false:
fermented foods are full of probiotics
false
what are the 3 main reasons fermentation is carried out?
- Preservation
- improvement of digestibility
- Addition of nutrients and flavours
