Bacteria

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Name 5 features of bacteria
ubiquitous, persistant, diverse, small and absence on nuclear membrane
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Describe the process of binary fission in 3 steps
1) DNA uncoils and replicates 2) DNA is pulled apart to separate poles 3) growth of new cell wall begins to separate bacterium until fully developed causing complete split
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Give 5 properties of bacterial dna
1) single, circular genome 2) highly supercoiled 3) non allelic (single copy of genes 4) sometimes posses plasmid with non-essential genes 5) all mutations visible
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What does bacterial 'sex' describe? How does it occur? What is it a source of?
Horizontal gene transfer. pilus on donor recognises receptor sites on recipient (then transfers ** plasmid). variation within bacteria.
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Name 3 uses of bacteria
WW treatment, bioremediation (breaking down hazardous substances into less toxic substances), biowarfare (using bacteria to kill other humans in an act of war)
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What is the name of the single bacterial chromosome?
Nucleoid
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What order do the membranes go in? (inwards out)
cytoplasmic, cell wall, capsule
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What are the three functions of cytoplasmic membrane?
1) permeability barrier 2) protein anchor (i.e. site of many proteins involved in transport/chemotaxis) 3) energy conservation (site generation + use of proton motive force)
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What is the size of bacterial genome?
500kbp-9000kbp
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Which would travel furthest on a gel: supercoiled plasmid, nicked circular plasmid, linear DNA
S/C (fastest) , then linear, then nicked (slowest)
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What are plasmids encoding antibiotic resistance referred to as?
Gene cassettes
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What is quorum sensing a regulation of?
Expression of virulence factors
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Inside the cell, ____ binds _____, which triggers ______
autoinducer (AIP), activator, transcription of specific genes
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In the quorum sensing of S.aureus, what is (a) AgrB (b) Agr D (c)AgrC (d) AgrA
(a) the signal peptide transporter (b)AIP precursor protein (c) peptide receptor (a histidine kinase) (d) response regulator
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What does AgrC do upon recognition of AIP
It autophosphorylates itself and transfers phosphoric group to AgrA- which then binds to P3 promoter and induces synthesis of RNA III
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Describe the structure of AIP before and after processing
Starts linear, but becomes cyclic after processing (mechanism involves addition of S by AgrB)
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What is the name of the promoter which promotes agr operon?
P2
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What does the transcription of RNAIII do?
RNA III remains in cytoplasm where it interacts with the RNA molecules that are homologous
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Give an example of an mRNA that it might bind. What does it encode?
h1amRNA, alpha toxin
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Describe the structure of h1amRNA without RNAIII added to it. What does this block?
Hairpin loop formed by 2 complementary sections of RNA coming together. Blocks SD sequence - and hence blocks alpha toxin translation
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What is the SD sequence?
"Shine-Dalgorino" sequence- ribosomal binding site 8bp upstream of start codon
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What does RNAIII do? Therefore?
Binds to region of h1amRNA that prevents it from binding to itself downstream. SD sequence is unblocked- so translation of alpha toxin can occur
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What does alpha toxin do?
Punches holes in our cells
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What is the name of the bioluminescent marine bacteria?
Vibrio fischeri
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Where do they colonise?
Specialised crypt (light organ) of immature bobtail squid
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What is the bioluminescence coded for by?
The lux operon (luxCDABE)
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What does (a) Lux I (b) Lux A and B (c) lux C, D and E code for?
(a) autinducer synthetas (b) alpha and beta subunits of luciferase (c) codes for enzyme that produces substrate for luciferase
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Give two examples of mutualistic relationships of bacteria
nitrogen fixation (bacteria in nodules of roots of legumes), and bioiluminescence (v.fischeri colonise specialised crypt of immature bobtail squid
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What is the latin name for the bobtail squid?
Euprymna scolopes
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Which type of bacteria is quorum sensing most common in?
gram negative
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Give two examples of pathogenic bacteria and what they do
S. aureus- causes sinusitis and food poisoning. E.coli- causes food poisoning
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Name the 4 different strains of pathogenic E.coli, and what they stand for
1) ET(oxinogenic)EC 2) EP(athogenic)EC 3) EI(nvasive)EC 4) EH(aemorrhagic) EC E=entero x=? E=escherichia C=coli
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Describe how ETEC invades cells
Binds loosely to fimbraie, secretes toxins into gut (gains entry without disrupting the cell membrane)
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Describe how EPEC invades cells
Destroys border microvilli (cannot absorb water- causing diarrhoea). attaches via actin-actin binding pedistal
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Describe how EHEC invades cells
Same as EPEC but also liberates shiga toxins
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What do the shiga toxins do?
Taken up by epithelial cells in coated pits and taken to golgi-->cell death
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Describe how EIEC invades cells
escapes from immune system by ingesting phagolysosomes and gains entry to neighbouring cells by and bursting through and digesting membranes
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What does chemotaxis describe?
motile bacteria swimming towards attractants and away from repellants by sensing the change in the concentration of a chemical over time (NOT the absolute concentration)
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How does it differ to quorum sensing?
It involves regulating the activity of existing flagella, rather than transcribing genes encoding flagella
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What direction do most flagella turn?
Anti-clockwise
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in the absence of a signal, what happens?
atleast 1 flagella will turn anti clockwise every few seconds
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What is tumbling?
A random (direction is random) but biased (only tumbles when necessary) process
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What does the hook do?
attaches flagellar filament to protein rings embedded in PM
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What forms the rotor?How fast can it rotates?
The rings 100rps
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What is the stator? Where is it found?
The outer ring of proteins that H+ flows through- it contains proteins responsible for switching direction. It is found tethered to peptidoglycan embedded in the inner membrane
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What are MCPs?
sensory proteins that sense the presence of attractants and repellants
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When do MCPs NOT respond?
When fully methylated
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What are the intermediary signal receptors?
CheW and CheA
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Which is the histidine kinase?
CheA
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What are the response regulators?
CheY and CheB
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What does CheY-p do?
phosphorylates FliM to induce tumbling
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What does CheB-p do?
Demethylates MCPs to make them more responsive
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What does CheZ do?
de-p'ates CheY
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What is CheR and what does it do?
A methyl transferase- adds methyl groups to MCPs to make them less responsive
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What are 4 symptoms of cholera?
Rapid dehydration, acidosis, rice water stools and hypovolemic shock
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Where do cholera use chemotaxis to migrate to?
crypts of the lower intestine
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How does their chemotaxis differ from E.colis?
They use Na motive force, and a single polar flagellum
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How fast can cholera move?
60cell body lengths per second
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When flagella spinning counter-clockwise, what direction does cholera move?
Left
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What are multiple flagella called compared to just one?
Peritrichous flagella and monotrichous flagella
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Other cards in this set

Card 2

Front

Describe the process of binary fission in 3 steps

Back

1) DNA uncoils and replicates 2) DNA is pulled apart to separate poles 3) growth of new cell wall begins to separate bacterium until fully developed causing complete split

Card 3

Front

Give 5 properties of bacterial dna

Back

Preview of the front of card 3

Card 4

Front

What does bacterial 'sex' describe? How does it occur? What is it a source of?

Back

Preview of the front of card 4

Card 5

Front

Name 3 uses of bacteria

Back

Preview of the front of card 5
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