Unit 5: Microbial Competition and Cooperation 29

competition dependent on

nutrient uptake, metabolic rates, growth rates

density relies on ecosystem organism finds itself in

closer prime niche, higher density of population

niche overlap =

sharing resources

proteobacteria E. coli

fast growht rates and adaptability to aerobic adn anaerobic (gets to cafeteria first)

proteobacteria Vibrio cholera

attacks neraby cells with virulence factors and kills off competitive bacteria (kills everyone in cafeteria)

actinobacteria streptomycin

growslower and rely on production fo antibiotics that kill competing bacteria (poisoning cafeteria)

syntropy

microbes cooperate and work together to carry out metabolic pathways that neither can accomplish alone

syntropy in nitrogen example

diazotrophs fix nitrogen inot ammonia --> nitrifers use nitrogen in oxidation reactions

quorum sensing

cell-to-cell comunicatio, regulatory mechanism that assesses pop density

turn on/off trnascription based on large/small pop

what does quorum sensing regulate

biofilm formation, antibiotic production, motility, sporulation, competence

antibiotic production regulation

bacteria cna detect foreign bacteria nearby and signal production of antibiotics

motility regulation

cell movement reqauired in small pops to find hospitable areas, once in those areas motility reduced

virulence regulation

virulence factors usually not effective unless in abundance

sporulation regulation

bacteria can detect changes in environment that can trigger creation fo spores

competence regulation

ability to uptake foreign DNA triggered in areas of large pop

biofilm

population fo cells enmeshed in extracellular polysaccharide (sugar) matrix that is attached to surface

niofilms protect from...

chemicals, phsyical barrier, dehydration, UV, pH and temp changes

biofilm formation

1. attachment

2. colonization

3. development

4. dispersal

eventually biofilm become inhospitable to bacterial growth because...

pH changes, oxygen limitation, nutrient depletion, toxin accumulation, physical stressors

results in bacteria dispersing (become motile and travel to hospitable environments)

biofilms spatially diverse

outer layer aerobic, inner layers anaerobic, interior more prone to nutrient limitation since nutrients must pass through outer layer, inner protected from antibiotics