Bacteria from essays

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  • Created by: LUFCMazza
  • Created on: 01-05-20 14:51
Bacteria- G+ bacteria, gram staining, cell wlal, peptidoglycan, teichoic acid, lysozyme sensitivity, outer membrane, porins, flagelli, toxins, pilli, mesosomes?
Gram stain= dark purple, cell wall= single layered, thick PG layer (80%), teichoic acids present, cell wall sensitive to lysozyme, no outer membrane, no porins, flagelli preesnt, produce exotoxins, have pilli, prominent mesosmes
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Gram negative bacteria?
Stain red/pink, bilalyered cell wall, thin PG layer (2-13%), no teichoic acid, less sensitive to lysozyme, outer membrane contains LPS, have porins, have pilli, produce endotoxins, have flagelli, less prominent mesosomes
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Colour after gram staining?
+ dark purple - Red/pink
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Cell wall
+ single layered - bilayered
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Peptidoglycan
+ thick PG layer (80%) - thin PG layer (2-12%)
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Teichoic acid
+ present - absent
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Lysozyme
+ sensitive - less sensitive
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Outer membrane
+ no outer membrane -outer membrane contains LPS
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Porins
+ Absent - Present
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Flagelli?
Both have
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Toxins
+ exotoxins - endotoxins
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Pilli
Both present
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Mesosomes?
+ more prominent, - less prominent
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Gram positive cocci?
Staphylococci, streptococci, enterococci
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Gram positive rods?
Actinomyces, bacillus, closriduim, diptheria, listeria monocytogens
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Gram negative cocci?
Neisseria, Moraxella
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Gram negative rods?
Most others eg. campylobacter, legionella, E.Coli, pseudomonus, proteus and salmonella
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Gram positive bacteira have a continuous cell wall w/high peptidoglycan content- peroperties of the peptidoglycan?
PG bacbkone is highly cross linked with *oligopeptides* and is the target site for B-lactam antibiotics.
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How do B lactam antibiotic work?
inhibit teh transpeptidase enzyme repsonsible for cross-linking. This prevents PG synthesis in new bacterial cells= bacteriostatic effect. Autolytic enzymes in cell wall are alos activated
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Peptidoglycan is also susceptible to...
endogenous lysozyme which cleaves the GB in the glycan backbone of the PG
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Why is the PG layer of G+ bacteira important immunologically?
PG is a PAMP recognised by NLRs of host cells such as macrophages. Thus, the presence of G+ bacteria stimulates release of inflammatory cytokines, activating immune response.
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What emanates from dead cells of streptococci?
the cell wall PG and the complex of C polysaccharide
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G- envelope and wall?
An inner membrane, an outer membrane and a thin layer of peptidoglycan.
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What does the outer memrbaen contain?
A LPS layer
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Functions of outer membrnae?
permeability barrier against compounds such as bile so G- tend to be enteric, production of OMVs and a target for insertion of teh MAC
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OMVs and MAC?
Host antibodies bind to OMVs rather than bacteirum and these act as a decoy mechanism- immune evasion (but bacteria more susceptible to lysis by the MAC).
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This means that...
G- bacteria are more prne to lysis by complement than G+ as MAC mediates bacterial lysis in the terminal effector stage of complement pathway. G+ instead targeted mainly by opsonisation.
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LPS?
THis is an endotoxin complex which produces endotoxic shock. Lipid A is the endotoxic portion of the LPS, it binds to TLR-4 producing inflammatory cytokine production. Inside cells Lipid A binds capsase-4 to induce cell death. Given its significance
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...
in septic shock, Lipid A is targetd by antimicrobial peptides (AMPs)
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Lipid A binds...
capsase-4, incuding cell death
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Core polysaccharide
consists of 5 sugards bound to Lipid A via KDO and outer core sugars
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O-antigen?
Neisseria genus possessa non enteric O antigen
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Are G+ and G- prone to penicillin?
G+ is as penicillin acts on PG layer but G- aren't as PG layer is protected by LPS so beta lactams don't work. Instead, ue KDO-8P synthase inhibitors.
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What drugs can exploit porins?
Drugs such as tetracycline thus target G- solely as porins aren't present in G+.
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What is the main porin of P.Aeruginosa?
OprF
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There are also Type 3 secreiton systems foudn in the cell wal of G- bacteria. What's used?
T3SS inhibitors
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G+ bacteria cell walls have teichoic acids. What are the 2 main types and what do they do?
Wall teichoic acids and lipoteichoic acids- they provide cell shape, grwoth and devision and provide resistance to AMPs. May also bind to TLR2. Very important to S.Aureus in helping adherence to nasal cells.
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Pilli?
Found almost exclusivley on G- bacteria-- mediate attachment of bacteria to receptors on the sruface of host cells. Longer sex pili bind male specific bacteriophages and atach cells to eahc other in connjugation.
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Type IV pili can bind what?
To the cerberal endothelium
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E. Coli has hwat?
A type I pilus implicated in UTIs
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What do capsules do?
high MW polymers which provide molecular mimicry and can express factor H binding protein- factor H is a negative regulator of the alternative complement pathway
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Card 2

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Gram negative bacteria?

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Stain red/pink, bilalyered cell wall, thin PG layer (2-13%), no teichoic acid, less sensitive to lysozyme, outer membrane contains LPS, have porins, have pilli, produce endotoxins, have flagelli, less prominent mesosomes

Card 3

Front

Colour after gram staining?

Back

Preview of the front of card 3

Card 4

Front

Cell wall

Back

Preview of the front of card 4

Card 5

Front

Peptidoglycan

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Preview of the front of card 5
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