Module 10: The Human Microbiome

• what are the 4 main bacteria phyla in the human microbiome?

  1. bacteriodetes
  2. firmicutes
  3. proteobacteria
  4. actinobacteria
• how do humans acquire microbiota?

  1. in utero, oral microbiome of the mother is transferred to the placenta
  2. during birth
  3. from breast milk
• what are the 4 roles of the microbiota?

  1. nutrition
  2. barrier/protective function
  3. immune function
  4. community function
• what are the 2 sites of microbial colonization?

  1. dry epethilia: skin
  2. moist epethilia: mucosa
• where are microbes found in skin?

  skin surfaces, glands, and hair follicles
• the skin microbiome is influenced by sebaceous glands, encourages growth
• dry skin has greater diversity
• moist skin commonly has staphylococcus
• staphylococcus provides barrier defense and anti-microbial peptides, inhibits inflammation
• where do you find moist epithelia?

  respiratory tract, gastrointestinal tract, urogenital tract
• in the GI tract, there is a large microbial population in the mouth and large intestine
• the lower GI tract is more heavily colonized, slower transit and more neutral pH
• how is the anaerobic GI tract different from the rumen?

  fermentation produces nutrients but not the majority of nutrition
• there is a significant amount of immune tissue around the GI tract
• how does gaining weight change the microbiome?

  hight fat diet lacks flavonoids, microbiome shifts toward flavonoid-degrading bacteria
• what happens to the microbiome when you diet after gaining weight?

  dieting increases flavonoids but microbiome degrades them
• how do flavonoids impact weight?

  decrease food intake, increase activity and energy expenditure
• what happens when you supplement with flavonoids?

  decrease weight gain and blood glucose levels
• the oral microbiota is the most conserved microbiome, extensive microbe-microbe interactions
• akkermansia muciniphila is common in the animal GI tract
• what is the role of akkermansia muciniphila?

  mucus degradation, beneficial to animals
• how is akkermansia muciniphila an advantage to bacteria?

  doesn't compete with other microbes
• how is akkermansia muciniphila an advantage to the community?

  liberates olligosaccharides
• how is akkermansia muciniphila an advantage to the animal?

  • expands mucus to make larger, more protective barrier
  • recycles some mucin as food for epithelial cells
• dysbiosis: disease may be consequence of disruption to normal microbiota
• dysbiosis can cause an increase in...

  1. allergies
  2. immune disease
  3. inflammatory diseases
• how does dysbiosis increase allergies?

  increase in sanitation decreases antigen exposure
• what is diet induced atherosclerosis?

  • gut flora metabolizes choline to TMA
  • liver converts to TMAO
• what is TMAO linked to?

  cardiovascular disease, plaque formation
• what other nutrient causes diet-induced atherosclerosis?

  carnitine (red meat)
• why is diet-induced atherosclerosis not seen in vegans?

  diet suppresses microbiota that converts carnitine to TMA
• probiotics: pure cultures of microbial strains
• prebiotics feed probiotics
• what are the functions of probiotics?

  exclude pathogens, modulate immune response