Unit 5: Animal Symbiosis 31

defensive symbiosis

symbiotic microbe protects host from infection by other microbes

leafcutter ants

have defensive symbiosis with bacteria Pseudonocardia

obligate mutualistic relationshipwith fungus that is susceptible to infection that kills both organisms

Pseudonocardia produces anti-fungal drug that kills infection but not fungus

termites gut symbiosis

have diet that requires digestion of cellulose

house extracellular bacterial symbionts that help with digestion

mutualistic relationship

termite gut mechanism

cellulose degredation in handgun, that has spatially diverse microbial community

exterior aerobic, interior anaerobic

fermentation of cellulose produces metabolites for host

termite gut diversity

16S rRNA analyzed to find phylogenetic diversity

2 main phyla overexpressed (spirochetes, fibrobacteres, archea)

produce glycosyl hydrolases that hydrolyze cellulose

Hawiian bobtail squid bioluminescence

have organ that has A. fischeri that at high populations, make protein luciferase that makes fluorescent compound

Bioluminescence in Squid

only occurs at high concentrations

regulated by quorum sensing, done through secretion of signaling molecule (acyl homoserine lactone (AHL))

Bioluminescence mechanisms

A. fischeri has bioluminescence operon (lux) is off by default

operon encodes gene luxI that produces protein LuxI which creates AHL

at low [ ] AHL lost to environment + expression off

at high [ ] AHL diffuses back into cell where binds LuxR (activator) that has conformational change and turns on lux operon producing luciferase

ruminant symbiotic relaitonships

herbovires that have rumen

rumen

specialized foregut digestive organ that digests celluose

rumen diversity

strictly anoxic compartment made up of firmicutes and bacteriodetes and archea that are methanogens