9 - host-bacterial interactions Flashcards
colonisation factors
entry adhere invade grow pathogenicity
whats the most common disease in humans?
tooth decay
bacteria get into body, adhere, stick to outside of teeth, produce toxins (acids), decay enamel, get underneath enamel, causes cavity
can cause sepsis if it gets into the capillary system
what are the 2 potential abilities of bacteria?
motility
adherence
what are biofilms?
communities of microorganisms that attach to each other and to surfaces
major problem on medical devices
what is biofouling?
accumulation of microorganisms on wetted surfaces
• water systems
• ship hulls
what do biofilms tell us about bacterial life cycles?
when free (motile) = planktonic
when sessile = community
requires a transition which is a gradient
both lifestyles exploited by pathogens
what are capsules?
polymers of sugar units
loosely encase a bacteria
function of capsules on bacteria
acts to hide cell from immune recognition
causes damage itself (in plants)
exploited in industry
fimbria
allow some degree of motility whereas a slime capsule doesn’t
attach depending on the condition its experiencing
• slow flow its detached as they want to find nutrients
why do bacteria secrete proteins?
to colonise, obtain nutrients and destroy competition
eg. haemolysin, toxins, enzymes
what do amylases do?
digest starch - energy
what do proteases do?
digest proteins - defence/energy
what do cellulases do?
digest cellulose - energy
what do levnasucrases do?
digest sucrose - defence/energy
protein secretion
is of either unfolded polypeptides or folded proteins
2 pathways across cytoplasmic membrane
• SEC - unfolded
• TAT - folded
what does SEC do?
facilitates insertion of proteins into the inner membrane
what are pathogenicity islands?
collections of genes which have been transferred and incorporated into the bacterium to express proteins that are pathogenicity factors
are either a selective advantage or cause bacteria to die
horizontal gene transfer
often assisted by phages
whats toxicity?
ability to cause damage by means of a preformed toxin
how do toxins act?
infect 1 site and damage another by releasing toxin
level of aggression is dependent on how they behave
what are superantigens?
overstimulate the immune system
what are enterotoxins?
specific group of toxins that act on the small intestine
what are neurotoxins?
often AB toxins that target nerve cells
what are AB toxins?
two-component protein complexes
• B binds to specific cell receptors
• B facilitates uptake of A
• A inhibits cellular processes or damages cell
whats the different between exotoxins and endotoxins?
exotoxins are secreted by bacteria
endotoxins are released when the cell lyses
