November 17, 2008 notes

1. Environmental stress-change in environmental conditions
a. Soil bacteria are good to look at for changes in conditions b/c soil environment is constantly changing
2. Quorum Sensing-change in bacterial gene expression at high populations densities
a. Autoinducers are released-small molecules that are continuously secreted by the bacterial cell; the autoinducer gene is constitutively expressed; at high population densities AI molecule binds to the AI receptor and leads to transcription of the quorum sensing phenotype genes
i. Homoserine lactone-autoinducer for gram negative bacteria
ii. Peptides (short sequences of amino acids)-autoinducer for gram positive bacteria
b. Components of Biofilms
i. P. aerguinosa a soil/water bacterium
1. Biofilms help protect against antibiotics which are produced by other soil bacteria
ii. Rhamnolipids
iii. Pyocyanin: an antibiotic (purple pigment)
1. Kills gram positive bacteria
3. A story about Armistice Day
a. Clostridium perfringens
i. Soil bacterium-has to deal with constant changing environment
1. Strict anaerobe
2. Spore-forming
a. Very durable, non-metabolic suspended state of Clostridium perfringens
b. Are spores because of the exposure to O2 leads to expression of a different sigma factor that allows for the transcription of all of the spore-forming genes
ii. Soldiers lived in trenches and bacteria got into their boots and grew then caused trench foot; hospitals were also in trenches and when people got hit by shrapnel there are anaerobic conditions under dead skin and causes gang grene
b. Virulence factors
i. Exotoxins-protein secreted by growing bacteria that does damage to us
1. Phospholipase-enzyme that destroys phospholipids (cell membranes)
a. Expression controlled by 25C sigma factor
2. Regulation of phospholipase gene expression
c. Acinteobacter baumanii
i. Similar to Clostridium perfringens

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