Structure Flashcards
What prevents bursting due to turgor
Cell wall
Which bact don’t have a cell wall
Mollicutes
Usually IC so in rel isotonic enviro
G-ve
Outer lipid mem cont LPS, Peptidoglycan layer, inner
Mem
Less rigidity
More impervious
G+ve
Thicker peptidoglycan layer cont anionic polymer eg teichoic acid, inner mem
Physically stronger
More permeable
Peptidoglycan layer comp and assembly
Chains of alternating NAM and NAG residues, regularly xlinked via peptide bridges to form rigid permeable mesh
Assembly by PBP enz (activity blocked by beta lactam antibios)
LPS fx
Hydrophobic barrier,
Resist phagocytosis
Lipid A component is a key PAMP recog by TLR4 (so known as an endotoxin)
Acid fast bact
Similar cw to G+ve with additional components alter staining prop so acid not removed initial stain so stain pink (non acid fast stain blue)
Capsule fx
Protect from dessication as is highly hydrated and from host defence as can affect large molecule diffusion and exclude them from cw
Can loosely bind bact cells together in colonies/biofilms
Capsule struct
Protective polysacc gel Some bact (eg bacillis anthracis) make with pp instead
S layer fx and bact
Bacillus anthracis
Campylobacter
Avoidance of host d
Adherence to host cells
Inner mem synonym
Cytoplasmic mem
Plasma mem
Elastic lipid mem
CM struct and fx
PL bilayer cont transmem pros and apparatus necessary for E production and nutrient transport
Highly hydrophobic and doesnt allow hudrophillic molecule diffusion so transmem transport dep on spec or non spec transport system.
Cont pros for assembling the Cw and is an attachment point for the chromosome
Organelles and metabolism
No mem enclosed organelles like euk cells
Does have spatial regulation of metabolic activities and incr evidence of cytoskel
Flagella comp
Filamentous pro polymer Pro sub units assemble to form helical structure embedded in CM and CW
ATP cause rotation and drive bact in resp to CM sensor activation (chemotaxis)
Flagella fx
Motility
Pros distinct from other cell pros so ID-able (salmonella and listeria)
(monomers recog by TLR5)
Can work as initial adhesin
Campylobacter flagella special fx
Can export pros out through flagella
Other motility forms than flagella
Endoflagella - corkscrew
Twitching
Gliding
Fimbriae/pili comp
Hair-like adhesins
Fimbriae pili fx
Bind to spec host cell surf rec, ECm components and EC ligands
Some specialised pili involved in coniugation
Other adhesion methods than pili
Inserted non filamentous pros that can act as adhesins
Other pros in cell wall can bind spec nutrients and form pores in outer mem
EC factors
Enzymes
Toxins
Effector pros
Why secr system required
Export pros and put pros into cell wall or build cell surface organelles
Sec system
Gen secr pathway that all bact have
Export pros in unfolded state
Req ATP
Exports most pros found in CM periplasm and CW and struct pros for other secr systemsb
Anchoring of exported pros in G+ve
Anchored to Peptidoglycan CW by sortase A which recog and cleave signal on the pro to be anchored
Anchoring of exported pros in G-ve
Must transport into and through outer mem too
Describe type 1 systems
2/3 pros form channelto export pros straight from cyt to EC
Use ATP to drive
Eg haemolysin export e.coli
Type 2 system
Chaperone-usher system
Used to assemble pili in outer mem
Type 3 system
Allow direct export cytoplasm to host cell so direct conduit built between 2 cells
Prod needle on bact surf that create pore in host cell
ATP used to export effector pro which can manipulate host cell fx for bact benefit
Flagella assembly occur similarly
Found in many G-ve pathogens: salmonella chlamydia escherichia
Type 4 system
Allow direct transport out (sometimes into host cell)
Incl bact conjucation systems eg VirB syst of Brucella abortus (used while bact present within host cell)
Type 5 system
Autotransporters
Single pro exported into periplasm by Sec system
Then orchestrate pore formation into outer mem sometimes with cleavage of a peptide that can act away from bact cell eg OM adhesins
Type 6 system
Homologous to sytem used by bacteriophage
Appear to be used by bact to inject factors to fight off other bact and virulence factor secr to target euk cell
Type 7 system
Mainly by acid fast to export CW assoc and secr factors
Mycobact assoc
Other secr method
Producing outer mem vesicles and by lysis
TLR1
Lipopeptides
TLR2
Lipopro and lipoteichoic acid
TLR6
Lipopeptide
TLR9
Motif in bact DNA (unmethylated repeated CG)
TLR 13
Spec bact ribosomal RNA seq
