MICR 2420 Lecture Notes - Lecture 9: Gut Flora, Bacteroides Fragilis, Microbial Mat

• School: University of Guelph
• Department: Microbiology
• Course: MICR 2420
• Professor: Emma Allen- Vercoe

Document Summary

Gut microbial ecosystems are highly variable in composition and abundance profiles between people. High diversity of species: healthy ecosystem, balance, functional redundancy. Low diversity of species: sick ecosystem, imbalance, functional disability, low gene count, susceptibility to damage. The human colon is a type of chemostat . How is the microbiota protective: competitive exclusion, colonization of a niche to prevent pathogen from growing there, environment modification, e. g. Lactobacillus colonization of the vagina drops the ph and creates an environment hostile to most pathogens: host stimulation, e. g. Bacteroides fragilis stimulates a host cytokine that regulates the immune system and prevents colonization by certain pathogens. Gnotobiotic animals: an animal where the associated microbiota is known and defined, includes germ-free" animals, expensive to manage but very valuable for microbiome research. Gnotobiotic animals have abnormal physiology: poorly developed immune systems, lower cardiac output, requirement for more calories to maintain body weight, thin, poorly developed intestinal walls, including stunted villi, abnormal ceca, odd behaviour, misshapen mitochondria.