Lecture 7 Flashcards
positive interaction
toxic product for one organism may be substrate for another e.g. cyanobacteria growing in pure culture die after 8 weeks but with a heterotrophic bacteria can survive for months bc heterotrophs recycle nutrients and waste
negative interaction
one microbe interferes with the growth of another e.g. antibiotic production by penicillium strain
competition
sulfate reducing bacteria outcompetes methanogens for substrates. add acetate, very little methane produced, add acetate and inhibit sulfate reduction, lots of methane produced
AgrA
autoinducing peptide (AIP)
AgrB
transmembrane protein that secretes mature AIP
AgrC
AIP receptor, binds AIP then phosphorylates AgrA
AgrA
response protein which activates P3 producing RNAIII
what does RNAIII do?
regulatory RNA controlling many genes:
- represses adhesion/cell wall comonents
- induces elements that drive invasion e.g. cytotoxins
biofilm
structured clusters of cells enclosed in a self produced polymer matrix and attached to a surface
what initiates the formation of biofilms
extracellular signals present in the environment
what are the 5 stages of biofilm development
initial attachment - flagella, type I pili
irreversible attachment - LPS, type IV pili
maturation I - microcolonies, produce alginate, repress flagella
maturation II - quorum sensing
dispersion - release planktonic cells
in pseudamonas aeroginosa what is twitching motility required for?
maturaton into microcolonies:
- express type IV pili
- induce alginate production (EPS)
- repress flagella expression.
what are the steps for twitching motility essential for twitching motility linked to?
sigma factor 22, encoded by algT
In vibrio parahaemolyticus, what does the flagella swtich to?
interference with flagella rotaton by a surface induces swarming motility - movement along a surface
