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 Predation on microorganisms by animals  Cultivation of microorganisms by animals for food and food processing  Commensal and Mutualistic intestinal symbionts  Digestion within the rumen  Mutualistic association of invertebrates with chemolithotrophic microorganisms 2

 Many invertebrate animals satisfy part or all of their food requirements by preying on microorganisms ( times smaller in biomass).  Two feeding strategies: → Grazing → Filter feeding 3

 Snails, sea urchins and limpets.  Scrape and ingest microbial crust from submerged surface.  The size difference between predator and prey is unimportant in this feeding because predator pursues coherent masses of million of microbes rather than individual prey. 4

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 Sessile benthic invertebrates that are permanently attached underwater and planktonic invertebrates that float and move in the water column exhibit filter feeding. 6

 The animals maintain a flow water using cillia and /or various modified organs, microorganisms are filtered from the water through gills, tentacles and mucous nets. 7

 Sessile benthic invertebrates: 1. Porifera (sponges) 2. Bryozoa (moss animals) 3. Sessile crustacean (barnacle, tube-building polychaete worms) 4. Lamellibranchiata (bivalves) 5. Brachiopoda (lamp shells) 6. Tunicata (sea squirts) 8

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 Various leaf-cutting ant populations maintain mutualistic relationships with fungi.  Ant → supply leaf tissue, disperse microbes by inoculating leaf segments, cultivate monoculture of fungus (fungal garden) and protect from competitor.  Fungal garden → Essential for maintenance of ant population  Atta species cultivate Agaricus 10

 Various wood-inhibiting insects such ambrosia beetles maintain mutualistic relationships with fungi (Monilia, Ceratocystis, Cladosporium, Penicillium, Endomyces, Cephalosporium, Endomycopsis)  Beetle → Maintain fungi within specialized organ known as mycangia or mycetangia, protect fungi from desiccation, inoculate fungal spores in wood tunnel and provide nutrients for spore germination, maintain favorable conditions, protect from invading microbes.  Fungi → Help beetle to digest cellulose 11

 Warm-blooded animals contain complex microbial communities within their gastrointestinal tracts.  The relationship of intestinal symbionts to their animal host can be characterized as commensal or moderately mutualistic. 12

 Animal provides microbes with a suitable anaerobic habitat and a steady food supply.  Intestinal microbes contribute to food digestion, produce vitamins for the host and by their presence help to keep out potentially harmful microbes. 13

 Lower termites maintain a mutualistic relation with microbial population found within their guts.  Protozoan and bacterial population ferment cellulose anaerobically producing CO 2, H 2 and acetate.  Acetate is absorbed through the wall of termite hindgut and is oxidized aerobically forming CO 2,H 2 O. 14

 Specific case of animal mutualism with intestinal microbes.  Ruminant animals: Deer, Moose, Antelope, Giraffe, Caribou, Cow, Sheep and Goat.  Ruminants have specialized chamber known as rumen.  These animals consume grasses, leaves and twigs rich in cellulose. They do not produce cellulase themselves but depend on microbial population within rumen for degrading cellulosic materials 15

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 Uniform and stable environment  Anaerobic sac  Temp:30 o C- 40 o C, pH:  Continuous supply of digested plant material permit development of very dense communities of microbes  Harbors a great diversity of microbes 17

 Cellulose digesters  Starch digesters  Hemicellulose digesters  Sugar fermenters  Fatty acid utilizers  Methanogenic bacteria  Proteolytic bacteria  Protozoa  Fungi (minor participant) 18

 Cows and other ruminants animals eat grasses and other plants containing starch, cellulose, pectin and hemicellulose which are transported to rumen.  Microorganisms within rumen convert these complex plant materials to LMW organic acids (acetic, propionic & butyric). 19

 Organic acids are absorbed into blood stream and oxidized aerobically to produce energy.  Ruminants also use proteins produced by microbial populations.  Fermentation by methanogens produces CO 2 and CH 4 that are expelled. 20

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