Parasites and Symbionts

List the features of mitochondria and chloroplasts shared with bacteria

• Circular DNA

• 70s ribosomes

• Double membrane, porins

• Binary fission

Describe anatomical features of the GI tract involved in an animal’s symbiotic relationship with its microbes for termites, monogastrics, ruminants, and granivorous birds

Explain how cooperation, competition, and antagonism factors into microbe colonization and persistence in or on its animal/plant host

Range of interaction between microbes and other species

• Mutually beneficial

• Neutral

• Competitive

• Antagonistic

• Parasitic

Symbiosis

Mutually favorable interaction, at least one species benefits. (e.g., clownfish and sea anemones)

Mutualism

Symbiotic relationship where host and microbe both benefit in some way from interaction

Hawaiian bobtail squid and Vibrio fischeri

• Bioluminescent bacterium colonize light organ in squid

• Light organ sucks them in and trap them

• Bacterium are fed by the squid host

• Host has access to anti-predatory adaptation at night

Peanuts and Rhizobium

• Peanut creates anaerobic environment and feeds bacterium

• Bacteria live in root nodules on the peanut plant’s roots

• Bacteria fixes nitrogen into a form the peanut host needs for growth

Bacteria-Eukarya symbiosis

Bacteria become internalized in eukaryotic hosts, evolve in function to resemble organelles

Endosymbionts

Organisms living within another organism’s body or cells, offering a mutualistic relationship

The “ultimate symbionts”

Mitochondria and chloroplasts

Cecum function

Absorption

Rumen function

Microbial fermentation, creation of VFA

Antagonistic microbe-microbe interactions

Competitors are out-competed, inhibited, killed, or “eaten”

How can antagonistic microbe-microbe interactions benefit the host?

Microbe competition could exclude member species that might cause disease