molecular microbiology Flashcards
1
Q
how did microbes change the world
A
earth was anoxic, 2.5 bil years ago prototrophic cyanobacteria started producing O2
2
Q
what are bacteriophage
A
viruses that infect bacteria
3
Q
how does the tree of life base classification
A
sequences of small subunit rRNA
why:
present in all cells
highly conserved sequences (through evolution remained pretty much the same)
a large enough gene length for phylogenetic analysis
4
Q
drawbacks of tree of life classification basis
A
not all microbes are culturable
primers used may not amplify divergent sequence (predetermined primer isnt gonna complementary to codons so isnt applified)
unexpected results can sometimes be disguarded as artifacts
5
Q
whats so different about the alt tree of life
A
metagenomic approach (sequence all dna in environment to onstruct draft genome)
sequence of 16 ribosomal proteins based
based on more information
eukaryotes and archaea closely branched together
prokaryotic lineage isolated
6
Q
what do bacterial genomes contain
A
chromosomes: single circular chromosome
and mobile elements:
bacteriophage
transposon (elements of genomes able to move throughout the genome )
plasmid
7
Q
why does the genome change over time
A
mutation and lateral gene transfer
8
Q
how does lateral (horizontal) gene transfer work
A
3 mechanisms : transformation - take on genetic information from environment), transduction (from bacteriophages) and conjugation (contact transfer)
enables bacteria to aquire and delete parts of their chromosomal DNA
9
Q
how does transduction work
A
occurs if bacterial DNA is integrated into the capsid forming a transducing partical. A transduced cells has to integrate the DNA into its own genome for replication unless it contains an origin for replication
10
Q
how does transformation work
A
mechanism used by gram negative bacteria, gram positive bacteria and archea
Environmental DNA binds to DNA binding proteins
uptaken as single stranded DNA
Taken up into the DNA of bacteria via homologous recombination using RecA proteins to join to DNA
11
Q
what does competent mean?
A
any bacteria able to undergo transformation
A cell can be forced to be competant
12
Q
inform me about plasmid
A
by definition they contains nonessential genes if it gains a core gene it stops being a plasmid and becomes a chromid
cannot integrate into a chromosome
13
Q
some features required in expression plasmids
A
origin of replication
multipul cloning site to insert genes
a promoter upstream of the multiple cloning site
a selectable marker such as antibiotic resistance gene
14
Q
uses of plasmids
A
recombinant expression to create medicines such as insulin as higher yields
15
Q
how are plasmids used in recombinant expression
A
transform competant host cells with plasmid
use selectable marker to screen for colonies with the plasmid
culture cells under conditions that lead to induction of overexpression
confirm presence of protein of interest (eg by SDS PAGE)
16
Q
what is the relationship between genome size and protein number
A
positive correlation
genes are organised into operons
17
Q
whats different about transcription in bacteria
A
its coupled with translation because theres no nucleus it occurs as translation occurs
this is energetically expensive so important to regulate and activate the right genes at the correct time
18
Q
3 stages of bacterial transcription
A
initiation, elongation and termination
19
Q
what is the transcription unit
A
a seuence of DNA transcribed into a single strand of mRNA starting at the promoter followed y the coding sequence and ending at the terminator
RNA may be polygenic if more then one gene is in an operon
20
Q
why are operons useful
A
they code for multipul genes of similar function together to form 1 polycistonic mRNA which are controlled as a single transcription unit
21
Q
features of Bacterial RNA polymerase
A
multisub unit enzyme
contains a groove wheres DNA is accomadated
groove is positively charged
2 forms core and holoenzyme
22
Q
whats the difference between the core bacterial RNA polymerase and the holoenzyme
A
they are exactly the same with the exception of a sigma factor in holoenzyme
23
Q
how holoenzyme works
A
sigma factor enables the holoenzyme to bind specifically at promoter sites.
sigma factor subunit is key in transcriptional regulation.
allows for specisivity allowing to regulate gene expression
24
Q
RNA transcription initiation
A
- Holoenzyme binds DNA.
Closed binary complex forms - DNA melting;
Open binary complex forms - RNA synthesis begins, forming ternary complex;
Abortive Initiation - Promoter clearance;
start of elongation;
σ may be released
25
what is a consensus sequence
A ‘consensus sequence’ is constructed by aligning all known examples and defining which is the most predominant/conserved base at each position.
26
lactose catabolism
this occurs in the Lac operon
in absense of glucose bacteria hydrolyse lactose
27
cis acting sequence
a sequence of DNA that does not create products that can diffuse through the cell
28
transinducing factor
DNA which encodes diffusable products
29
transcription factors
Proteins which interact with RNA pol to initiate transcription act as activators to turn on gene expression
30
positive regulation of Lac operon
CRP is an activator protein that binds to a target
sequence adjacent to the promoter.
A dimer of CRP is activated by a single molecule
of cAMP.
CRP introduces a 90º bend into DNA at its binding site.
31
Key features of an expression vector:
Origin of replication: For plasmid replication
Multiple cloning site: region to insert gene of
interest
Selection marker: Ampicillin resistance gene
Promoter: T7 promoter – (T7 RNA pol binds
T7 promoter)
LacI repressor gene- LacI protein represses
transcription until desired point
32
What is a virus
nucleic acid surrounded by a protective protein coat
its replication is host cell dependent
have intracellular and extracellular phases
33
how does viral transmission work
relies on
infecting a host
replicating in a host
infecting the next host
repeating the steps again
34
what is a viron and its structure
viron = intact viral particle
-nucleic acid surrounded by protective protein capsid as a base
highly repetitive capsid form
vary widely in shape and chemical composition
attachment is mediated by viral receptors
some are surrounded by a membrane = enveloped virus
35
nucleic acid directionality
DNA and RNA have directionality
conventionally mRNA is positive sense and the complimentary strand is negative sense
the directionality dictates the machinery required to replicate the viral genome
is an RNA is the right directionality it can directly function as mRNA
as a result transcription in viruses can be the conversion of negative sense RNA to positive sense RNA
36
viral genome replication
there are many different methods dependent on the nature of the viron
RNA dependent RNA Polymerase - the RNA virus must either encode this gene or carry RdRP in their virons
Reverse transcriptase: must be encoded by retroviruses to produce DNA intermediate
encode three categories of proteins:
-structural proteins needed for progeny viral protein
-immunomodulatory proteins to interfer with host immune defence
-enzymes for genome replication
37
what is the virus hypothesis
viruses predated cells and supported the rise of cellular life
A lot of viral genomes incode for genetic sequence lack any cell derived origin
alternatively all known viruses need a cellular host to replicate
38
What is the reduction hypothesis
the idea that viruses used to be cells and are the reduced form of parasitic organisms
this is supported by the discovery of giant viruses
39
what is the escape hypothesis
viruses were once part of the genetic material of host cells but escaped and evolved by taking genes through horezontal gene transfer
though this is fails to explain structures completely unique to viruses
40
what is genome mosaicism
many phage genomes contain regions with distinct evolutionary origins
41
why is it difficult to map viral phylogeny
no universally conserved genes
few genes and rapid evolution
polyphylogenic - no clear ancestor
42
approaches to understand viral diversity
1. cuturing and microscopy - quantitive analysis of physical aspects of the virus
2. metagenomics - identify biological patterns between viral communities, expanded view on viral sequences
3. single virus genomics - looks into the microdiversity and genetic heterogenity (genetic differences)
All of these techniques should be used in combination when possible as there are limitations to all
43
how are microbes cultured on solid media
Everything prepared under sterile conditions
growth media - mix of reagents to provide nutrition and physiochemical conditions that is mixed with a gelling agent (such as agar) solidifying it in a petri dish.
inoculated onto surface and allowed to replicate
44
how are microbes cultured on liquid culture
growth media - mixture of reagents providing nutrition and suitable physiochemical conditions
different medias are suitable for different micobial species
aerobic organism require vigurous agitation and therefore require to be stored in a shaken flask
45
how to sample microbes more closely resembling there natural environment
winogradsky column - allows for controlled experimental set ups sampling from natural environments allowing for many different types of microbe to grow
46
ways of measuring microbes
mass - known volume culture used allowed to grow then dried and reweighed
cell count - can be done via haemocytometer (manual: accurate but time consuming),
flow cytometry(automated using lasers, counts and characterises individual cells detailed info including size and complexity),
viable numbers (counting colony-forming units providing information on colony morphology)
proxies - turbidity (cloudiness measurements quick and easy but cant differenciate alive and dead cells)
ATP measurement (ATP bioluminescence assays light up when detect ATP in living cell does not distinguish between microbial species)
Molecular methods (PCR and qPCR used to quantify specifci DNA or RNA markers
47
why does stationary phase occur
reaches limits of the plate more bacteria cant grow as theres no more space and microbes die and are replaced but still continue to live as unlimited nutrients
48
how do bacteria grow
aquire nutrients from its environment and build new biomass from this.
increase in biomass leads to increase in ionic strength and more uptake of water by osmosis
49
what prevents bacteria cells from growing indeffinately
cell wall cant expand under pressure so as the cytoplasm increases turgor pressure builds leads to the cell wall producing more peptidoglycan units to grow the wall.
This addition of units forms a septum in an attempt to not compromise the structural integrity of the cell which leads to binary fission
50
how does binary fission work in most bacteria
controlled by a cytoplasmic protein called FtsZ which forms a circular polymeric ring in the mid line of the plasma membrane.
This ring contracts with the formation of the septum in the cell wall. the coordination of the contration and septum formation leads to the splitting og the cytoplasm in 2
DNA replication is initiated a origin site of genome, which contains multiple binding sites for replication inhibitor Dna A.
As cell volume increases DnaA molecules increase proportionally. When the volume of DnaA is sufficient DNA replication occurs creating a new origin site.
The 2 origin sites a drawn towards opposite poles of the cell leading to segregation of the DNA into the two daughter cells
51
how is a bacteria capable of replicating quicker than the time taken for DNA to replicate
multiple replication forks
52
common features of viral replication
virus recognise and attach to specifci receptor on host cells
The RNA or DNA is uncoated from protein and released from virus particle
The virus uses the host to make viral nucleic acid and capsid and assembled in the cell
the new viruses are released into the environment (often accompanied by host cell lysis)
53
Why do many microbes uses nitrogen as a source of biomass
generally many living things can quite simply convert fixed nitrogen from one form to another
It can also be used in sparse oxygen conditions respiratorily
supports the nitrogen cycle proving nitrogen to low nitrogen areas.
54
How do microbes work around nitrogens general unreactivity
use a cofactor containing iron sulfur and molybdenum for nitrogen fixation purposes which accompanies the nitrogenase enzyme.
55
what are the specific parts of nitogenase that make it good for nitrogen fixation
NifHDK proteins form the central unit, their assembally requires production of FeMoCo cofactors and electron transfering iron-sulfur clusters (including the P-cluster)
issue as O2 actually competes for binding at the N2 site which is really bad as prevents nitrogen fixation so theres a protein complex which takes 3 different forms
: klebsiella has gene expression control so nitrogenase only made in nitrogen starvation and limited oxygen,
Anabaena photosynthetic nitrogen fixer to spacially segregrate nitrogen fixation from site of photosynthesis
Rhizobium forms symbiotic relation with plant roots to protect nitrogenase from oxygen toxicity.
56
regulation of nitrogen gene expression
RNA polymerase consists of core tetramer alpha 2 beta beta and an additional protein called sigma factor 54 sometimes called sigma N . Sigma N is encoded for by gene rpoN. Forms interaction with NifA.
The availability of NifA to bind to nif promoter regions controls nitrogen fixation
NifLA: NifA and NifL dimerise to prevent binding to DNA, under reducing conditions disociation allows NifA to bind
NtrCB: sensor-regulator NtrBC controls nifLA. NtrB senses nitrogen availability, at low concs acts as kinase phosphorylating NtrC. That binds to the promoter of nifLA
57
Why is iron problamatic in iron rich environments
iron exists as Fe3+ is oxygen rich conditions which is insoluble which limits its ability to make cells
under very rich o2 conditions the iron reacts and in instances such as the fenton reaction this can form hydroxyl radicals which can damage DNA and cells
58
what are the stategies that bacteria use to get iron
siderophores: small chelate agents specific to Fe3+ bind with high affinity
Haemolysin: range set of substances that disrupt red blood cells causing them to release haem by forming pores in the cell membrane
59
how do microbes store iron
storage systems of ferritin and bacterioferritin
each are multimeric proteins which form a spherical shape and store up to a couple thousand ferric iron
60
how is iron regulated
direct means
Fur is a repressor gene that responds to iron starvation.
in the presence of iron FUR dimerises this enhances its affinity to DNA. This binding prevents RNA pol binding inhibiting transcription
61
What part of a viral genome tends to evolve the quickest
the spike proteins, affects its infectivity, transmissibility or facilitates immune escape (helps prevent antibody recognisition
62
importance of COVID spike protein
binds to receptor ACE2 for entry to cells mediates the virus-cell fusion process
varient D614G is one of concern as it has higher efficiency in entry (tends to infect younger patients)
had 23 mutations 8 of which in spike proteins
stalk inaccessible to antibodies as 90% glycan coverage
63
role of Hemagglutinin in influenza
receptor recognition on host cell, specifically sialic acid found on eurythrocytes and upper level respiratory tract cell
binds to mucins in mucus on the journey to epithelial cells
64
what is the role of neuraminidase in influenza
important - facilitates release of new virons by preventing reattachment to dying host cells which is why it
cleaves sialic acid groups from host cell glycoproteins (respiritory tract mucins)
facilitates cell exit
stops them from reattaching from the cell they have just left.
65
what is antigenic drift & shift
drift : gradual small changes (mutations) in genes of a virus resulting in changes in the surface protein of the virus. can lead to an epidemic -> more common because RNA genome doesnt possess a proofreading mechanism to remove mutations
shift : an abrupt major change in virus resulting in a new virus that may lead to a pandemic
can happen as a result of recombination forming a subtype
66
how can diseases jump species
species with similar receptor binding mechanisms can have diseases jump between them as a result of a series of mutations that aligns the mutation more closely to the other species receptor.
67
what is the lifecycle of T. brucei
digenetic - passes between 2 hosts
it is extracellular because of its surface proteins and a high level of antigenic variation
the parasite moves with flagellum tip in a corkscrew motion - allows movement to different parts of the host harbours multiple virulence factors
68
what is unique about t.brucei 's protein coats
has varient surface glycoprotein coat - the coat varies depending on the host it is in enables extracellular survival to combat immune recognition
VSG genes are expressed by metacyclic (insect salivary gland phase) and bloodstream (mammalian stage)
only one is VSG gene at once (theres aproximately 2500) which switches every 100 cellular divisions
the carbohydrates make the plasma membrane largely inaccessible N-linked glycans further reduce this
69
what are the 4 methods to produce new VSG genes and switch them
gene conversion - swap to another genomic location
segmental gene conversion - chimeric VSG produced from multiple recombinant events
telomeric exchange - uses the 70bp repeats to swap VSGs from 2 different ESs
ES switch - active one goes silent, previously silent ES becomes transcriptionally active
70
how do t. cruzi immune evade via molecular mimicry
trans-sialidases, mucins and mucins-associated surface proteins MASPs are the largest and most heterogeneous gene families.
the sheer number of surface antigen variants overwhelm the immune system capacity to raise specific antibodies against t.cruzi
the cell appears to be self to the human host immune system
71
techniques for studying bacterial cell surfaces
electron microscopes
freeze-fractured cells being imaged
characterisation of genes in biosynthesis of cell surface components
isolation and biochemical characterization of individual morphologic components of the cell
72
compare gram positive and gram negative cell surfaces
gram negative: cytoplasmic membrane medium sized
thin peptidoglycan in a periplasm and an outer layer with proteins running through LPS
gram positive: big cytoplasmic membrane with proteins throughout and large thick peptidoglycan layer teichoic acids and lipoteichoic acids.
73
what is the function of cytoplasmic membrane in prokaryotes
permeability barrier: prevents leakage znd gateway for transport of nutrients into and waste out of cells
protein anchor: site of protein that participate in transport, bioenergetics and chemotoxins
energy conservation: site of generation and dissipation of the proton motive force
74
what do transporter proteins do
allow cells to find solutes from the environment and allow them to be accumulated in the cell at a higher rate then just diffusion across the membrane
three categories:
simple transporter - transmembrane transport protein
group translocation - series of proteins chemical modification of substance
ABC transporter - a substrate-binding protein, a transmembrane transporter and an ATP hydrolysing protein
75
what strengthens the peptidoglycan layer
carbohydrate backbone : strengthens the x axis
cross linked peptides: strengthens the y axis
76
structure and function of teichoic acid
repeating unit of glycerol phophate or ribitol phosphate and carbohydrates linked by phosphodiester
regulation of ion homeostasis: metal ion sequestration - WTA biosynthesis is upregulated in metal limited conditions
-> lack of WTA leads to improper cell division
A nice target for antibiotics
77
What effects do lipopolysaccharide and lipoolgiosaccharide have
they are key factors of pathogenicity in gram negative
LOS involved in adhereance and invasion of host cells
LPS provides integrity to the cell and is part of the mechanism for bacteria to interact with other surfaces
they have rather large O antigens
the use of these glycoproteins elicits a inflammatory reaction from the immune system.
78
what are O- antigens helpsful for
they are great for classifying lineage of strains that cause disease
79
How is LPS assembled and transported across the periplasm
O-antigen subunits are translocated across inner membrane by wzx
polymerised by wzy
chain length determined by wzz
core lipid A translocated across IM by MsbA
Core lipid A molecules and O-antigen are ligated by WaaL
LPS molecules are transported across perimplasm LptA
LptD and E flip the LPS across the outermembrane
80
what is the function of the surface polysaccharides
attachment of the microorganisms to solid surfaces - forming thick biofilm
prevent dehydration
pathogenic bacteria enter body by specific bind specificity to surface components of host tissue
virulence factors
81
how does flagella dependent motility work
the colonisation and pathogenesis of many bacteria. flagella cost the bacterium in terms of growth rate
aggregate as a bundle to propel the cell in a forward direction
flagella proteins are glycosylated for the formation in bacterial pathogens
82
what are the environmetal factors to regulate flagellar biosynthesis
butyrate, mucin, bile salts, epinephrine/norepinephrine, mechanical cues, temperature, pH, osmolarity, DNA, ammonium concentration
83
how the pili functions and structure
protein based comprised of many repeating subunits produced by all gram negative bacteria and many gram positive bacteria contain this too
facilitates genetic exchange between cells in conjugation
enabling the adhesion of pathogen to specific host tissues before invasion
twitching motility along solid surfaces
84
what are fimbraie and there functions
protein structures that extend from the surface of a cell
enable cell adherence to surfaces
enable pathogen to form pellicles (thin sheet of cells on a liquid surface ) or biofilms (solid surface_
85
what is an extremophile
an organism that thrives in extreme conditions
obligate extremophiles must have conditions
facultative extremophiles can tolerate conditions
86
extremophiles temperatures for different types of organisms
fish - 40 degrees
plants - 48 degrees
eukaryotes - 60 degrees
hyperthermophiles - max growth over 80 degrees
most hyperthermophilic organisms are archaea
87
how to microbes break down pollutants
many microbes produce extracellular enzymes, they can allso produce free radicals that randomly break bonds in the compound.
These smaller fragments that break off can be taken up into the cell (called the smash and grab approach)
88
how microbes manage water insoluble compounds
surfactants such as : glycolipids, phospholipids, lipoproteins can be produced by the microbes
these are amphi[athic molecules
they migrate to the boarder og the oil with the hydrophobic tail pointing to the oil
these reduce interfacial tension allowing for more mixing and form micelle
this increases SA for attachment and pseudo-solubilses the oil
89
how to microbes detoxify pollutants
series of chemical reactions to deactivate including hydrolysis, hydroxylation, demethylation and methylation
90
what is recalcitrance
the ability fo a substance to remain in a particular environment in an unchanged form
91
conditions affecting biodegradation
microbial populations, metabolism, structure, toxicity, temperature, pH, surface area
92
what are biofilms
a thin layer that forms on top of some wet surfaces consisting of bacteria and other very small organisms
its estimated that 80% of bacteria and archael cells live in biofilms
93
why do microbes form biofilms
protection from harsh environments
reduces the need to 'swim' (allows them to stay near life)
facilitating cell-cell interaction
surfaces concentrate nutrients
94
what is a biofilm comprised of
adherent cells which are embedded in structure
slimy extracellular matric that is comprised of extracellular polymeric substances (EPS)
componants of EPS
- extracellular polysaccharides
-proteins
-lipids
-DNA
95
examples of where biofilms can be founds
on rocks in streams
industrially: trickle filters
medically: plaque on teeth, or on medical implants
96
steps of biofilm formation
association with the surface
- through week vand der waals and hydrophobic effects. Attach via single pole then longitudinal axis for irreversible attachment
robust adhesion- cells anchor more permanently using adhesion structures like pili, leads to surface induced gene activation
aggregation of cell into microcolonies - cells grown more complex and multicellular. characterised by different pillar like structures that are interspersed woth fluid filled channels. Small messenger molecules used for communication
growth and maturation - develop 3d structure cells driven by cellular crowding, chemical gradients and nutrient competition. This leads to the creation of subpopulations
dispersal - cells leave the biofilm structure and return to planktonic mode
97
limitations of the biofilm formation model
based on biofilms formed in flow cells and carried out on P.aeruginosa
-> not representative of all microbes and not a based in life environment which may effect behaviour
wide variety of biofilm structures obverved in real world systems
doesnt consider that the real world is open and therefore there is a continuous influx of new colonizers
98
why are biofilms important
they cyclic nutrients in aquatic ecosystems
cause the corrosion of submerged structures
play a crucial role in plant microbe interactions
wastewater treatment
they can colonise the drinking water distribution system prtotecting against pathogenic bacteria + maintaining standards
cause medical devise infections
99
ways to control and manage biofilms
surface modification
antibicrobial agents
physical disruption
UV light disinfection techniques
nutrient limitation
quorum sensing inhibition
100
what is quorum sensing
the regulation of gene expression in response to fluctuations in cell population density
bacteria produce and release chemical signal molecules called autoinducers that increase in conc as a gauge of cell density.
detection of minimum threshhold simulatory concentration leads to alteration in gene concentration
101
why do bacteria do quorum sensing
as a way of dictating its own population size
allows bacteria to hold back on doing costly processes for the greater good of the population until there's enough of one to warrant it
102
how does quorum sensing work in v.fischeri
LuxI produces an autoinducer molecules and releases it
As population grows so does conc of autoinducer
When the autoinducer reaches threshold concentration, it binds to receptor protein LuxR
the luxR autoinducer complex activates expression of Lux genes that are responsible for bioluminescence
103
What is the great plate count anomoly
only ~1% of microbial cells can be captured from the environment and grown using conventional culture based methods
104
what are the reasons for unculturability
some microbes grow too slowly
are too fastidious (specific narrow conditional requirements), a reliance on particular conditions (the conditions culturing is done under being ineffective), microbes reliance on other microbes prevents growth, syntropy (microorganisms from different strains/species are mutually dependent) and toxic build up
105
what are the key features of a suitable molecule for building phylogenies
universally distributed
similar or identical function
enough similarity to isolate or amplify from multiple sources
enough difference to distinguish sequences from one another
As a result 16S rRNA meets these requirements
106
what is the function of the gut microbiome
required for biosynthetic processes such as vitamin K, folic acid and some steroid hormone metabolism
fermentation of sugars to short chain fatty acid
buffers the body against pathogens
107
What affects the gut microbiome
random factors such as historical health events (vaginal to caesarean birth)
diet and antibiotic treatment can lead to rapid changes in microbial composition
disease can be correlated (such as IBS)
Environment (more so than genetics) are determinants of the gut compositior
108
concepts to explain infectious pathogenesis
1. the microorganisms must be found in abundance in all organisms suffering but not in healthy organisms
2. the microorganism must be isolated from a diseased organism and grown in pure culture
3. the cultured microorganism should cause disease when introduced to a healthy organism
4. microorganism must be re-isolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent
109
pathogenesis and its relationship to evolution
pathogenesis has evolved lots of times. there isn't a specific evolutionary group of pathogens
when this pathogenesis is carried by a highly specific virulence factor, they are highly prone to horizontal gene transfer adn therefore pathogen potential can spread.
pathogenesis has to serve evolutionary benefit for it to be passed on by the microbe. This is seen by how cholera causes diarrhoea to pass on the disease further.
Accidental pathogen is where a pathogen infects but cant infect future hosts it has no mechanisms
110
what is pathogenesis
pathogenesis is the qualitative capacity of an agent to cause disease, whereas virulence is the power of an organism to elicit disease severity.
111
how do we identify virulence factors
genomic approaches
can compare pathogenic and
non pathogenic computationally
explore regions that are
horizontally acquired (aquited
DNA tends to have more G + C
content
Experimental approaches
-gene expression under different
conditions that simulate disease
vs controls
-genetic methods - we can make
gene knockouts where all genes
are randomly targeted to be
disrupted. From this we can
explore the relative ability of a
given strain to survive and cause
disease in an experimental
disease model
Biochemical approaches
identify the cause of virulence
and characterise how this works
using mechanistic biology. This
helps to identify potential new
therapeutic interventions
112
examples of virulences factors
iron acquisition
exotoxins - gene products directly
cause host damage
adhesins - sticking to the surface is
important for colonisation
trafficking and subversion - subverts the cell by injecting a protein componant that affects intracellular signalling. some go further by invading the cell themself
actin re-modelling - some bacteria can interfer with cellular processes that control the cytoskeleton leading to the reorganisation of actin structures in cells
surviving stress - pathogens have a higher capacity to control ROS (reactive oxidation species) stress
113
what componant make up the cell envelope typically
outer membrane, peptidoglycan, inner (plasma) membrane, pili fimbrae
the only common feature between all is a plasma membrane
