Human Microbiome- Lecture 15 Flashcards
Variation of bacteria throughout the body
Changes depending on the site, influence physiology, immune function, metabolism and nutrient absorption
Predominant bacteria in gut
Bacteroidetes and Firmicutes
Conservation of gut microbiome
Conserved across geographic and cultural separation at phyla level, related individuals have higher similarity of microbiomes due to environmental and genetic factors
Functions of the Gut microbiome
(1) Protection against pathogen colonization
(2) Nutrient absorption, polysaccharide digestion
(3) Immune system development
How does the microbiome protect against pathogen
prevents adhesion to intestinal mucosa, consumes carbohydrates, consumes low abundant nutrients, Use of bacteriocins, use of CDI and T6SS
Generation of Germ-free mice
through antibiotic use or by being born and raised in sterile environement
C. Difficle
Spores do not germinate in healthy individuals, after antibiotic use that kills commensals, nutrient availability allows for spore germination and release of toxins causes disease
How do bacteria contribute to polysaccharide digestion
Soluble glycans, (small) can be digested by host enzymes, larger insoluble glycans require bacteria breakdown to short-chain fatty acids (propionate, acetate and butyrate), important for plant-derived polysaccharides
PUL system
polysaccharide utilization system found in bacteroidetes, digests specific plant and mammal-derived polysaccharides
SUS system
Starch utilization system, lipoproteins immobilize the glycol to the bacterial surface, A-amylase (glycosyl hydrolase) breaks down to the polysaccharide to oligosaccharides, Ton-B dependent uptake into periplasm by pulling on plug domain of OM porin, two more glycosyl hydrolases breakdown the oligosaccharide further to monosaccharides, then ABC transporters are used at IM
Observations of immune development in germ-free mice
do not develop organzized lymphoid tissue, cannot develop pro and anti-inflammatory states
Composition of the oral microbiome
Anaerobic and Aerobic bacteria, mainly streptococci
Periodontitis
(gum inflammation)
What causes caries (cavities)
Overconsumption of succours allows streptococcus mutants to ferment the sucrose to lactic acid, promoting acid-tolerating bacteria and causing demineralization of enal
Polyphromas gingivalis
Causes gingivitis, and promotes the P13K-dependent pathway not the MyD88 pathway, an inflammatory pathway that does not produce antibacterial factors. Inflammation causes tissue destruction, freeing nutrients.
