Lecture 281)Know why some herbivores are dependent on microbes a) Many herbivores contain many plant fibers but lack the enzymes necessary to digest those fibers (cellulose and others like pectin and hemicellulose), digestive enzymes of animals have evolved to promote growth of microbial communities that aid digestion offibrous plant materials2)Compare foregut fermenters to hindgut fermenters animals a) Foregut fermenters- Have some kind of chamber that is a rumen that is a microbial communityb) Hindgut fermenters- Have a pouch that contains microbial community3)Describe the sequence of events of ruminant digestion and know the major type of nutrients that pass through the rumen wall into the animal a) Ruminant digestioni) Food enters rumen where microbes begin anaerobic cellulose digestionii) Mixture goes to omasum and is concentrated by water adsorptioniii) Mixture does to a abomasum (true stomach); acid kills and digests food + microbesiv) Digested food + microbes go to small intestine for further adsorption of nutrientsb) Major type of nutrients passed through rumen walli) Cellulose and other fibers are degraded by microbes into simple sugars, volatile fatty acids that are passed through the wall into the blood stream. Examples: Acetate, Propionate, and Butyrate4)Understand that dietary changes can lead to microbial community changes a) Sudden dietary changes can produce significant changes in the makeup of the microbial community (dysbiosis).b) Switching from forage to a diet high in grains can favor growth of lactic acid-producing bacteria, this creates a pH drop in rumen, additional community changes result.c) Continued acid buildup causes damage to rumen and acidification of blood (acidosis). 5)Explain what the human microbiome is and describe the Human Microbiome Project a) Human microbiome is all the microbes on all sites of the body, most significantly the intestines, mouth, Upper reparatory, throat, stomach, urogenital tract and skin.b) Microbe cells out number human cells 10:1c) The human microbiome project is an ongoing research study to document microbial populations, diversity, and changes at many anatomical sites using 16S rRNA gene sequencing and metagenomic analysis. 6)Understand what parts of the human digestive tract contain microbes and how they benefit the human host a) Microbes are still essential for proper nutrition; gut inhabited by 3,500-35,000species.b) Consists of the upper gastrointestinal tract: mouth, esophagus, stomach, duodenum and lower gastrointestinal tractc) Microbial habitats change as food moves through the gastrointestinal tracti) pH- -------- acid---------neutralii) Oxygen- aerobic---anaerobic---------iii) Diversity- low----------------------high7)Understand the examples presented of human diseases and conditions that affect the digestive microbial community composition a) Beneficial effects of intestinal microbes includei) Vitamin synthesisii) Glycosidase activity break polysaccharide bondsiii) Steroid metabolism Bile acids microbes steroidsiv) Stimulation of immune systemv) Antagonism of pathogens b) Food microbes die vitamins human8)Compare horizontal and vertical transmission of bacterial symbionts a) Horizontal Transmission- Where symbiont comes form the environment b) Vertical Transmission- (heritable), where symbionts are passed down from a parent; no free- living stage in life cycle.i) Most heritable symbionts live inside insect host cells known as bacterioicytes. 9)Know the significant facts about the Buchnera and Wolbachia symbioses, and what a parasitic symbiont is a) Buchnera bacteria with pea aphids, aphid food source (sap) is low in amino acids b) Wolbacteria bacterial parasitic symbiont infects 20% of all insects.i) Infects sex cells of hosts and is passed from mother to child in eggsii) Produces toxin that only allows sperm from infected males to successfully mater with infected females. iii) Parasitic symbiopnt- when the parasite infects the hosts sex cells and its passed to the next generation10) Describe how the digestive microbial community of termites benefits their host a) Wood contains fibers like cellulose, hemicellulose, and lignini) Termites cannot efficiently use these as food directlyii) Has a very low nutrition value (exept for sugar monomers)iii) Beneficial symbiotic microbes live within the anoxic hindgut, where anaerobic digestion of wood fibers take place, providing nutrients to the termite.iv) Microbes break down fibers and carry out fermentation of the resulting sugars. 11) Describe how marine symbiotic bacteria benefit the Bobtail squid and the Riftia tube worm, and what occurs in the trophosome of the Riftia a) Many marine invertebrates are dependent on beneficial symbiotic microbes, including the Hawaiian Bobtail squidb) The Hawaiian bobtail squaid, like any other squid have symbiotic light-emitting bacteria living in a specialized organ.i) Aliivibrio fischeri is a marine bacterium that is acquired by horizontal transmission from the environment ii) Emits visible light in response to quorum sensing, where high population density in the light organ switch on genes for light productioniii) Organisms like the Riftia tube worms contain endosymbiotic chemolithotrophic bacteria living in sponge-like tissue known as a trophosome(1) Worm has no digestive system: bacteria provide all nutrients (2) Energy mostly from aerobic respiration using hydrogen sulfide aselectron donoriv) Other organisms in this habitat (clams and snails) are also dependent symbiotic
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