Microbiome in Human Digestion

• Microbial Distribution

  • Small intestine has fewer microbes, less studied due to invasive sampling.

  • Stomach was previously thought sterile; contains microbes like Helicobacter, which can cause ulcers.

• Dominant Groups in Gut Microbiome

  • Major groups: Firmicutes, Bacteroidetes, Actinobacteria, Proteobacteria.

  • Infants predominantly colonized by Bifidobacteria associated with health.

Diversity and Function of Microbiome

• Importance of Diversity

  • Loss of diversity in microbiomes (like gut) leads to impaired function and is linked to dysbiosis.

  • Different taxa contribute to digestion and immune stimulation.

• Infant Development and Microbiome

  • Establishment begins at birth, with alpha diversity (microbial variety in one sample) and beta diversity (differences between samples).

  • Initial microbial diversity is low, increasing with age as more taxa are introduced.

Factors Influencing Microbiome

• Colonization Factors

  • Vertical transmission from mother to child is crucial for initial colonization.

  • Factors like C-section vs. vaginal delivery affect microbiome establishment.

• Environmental Exposures

  • Hygiene hypothesis suggests exposure to environmental microbes is vital for microbiome health.

  • Infants in less sanitized environments may have better immune conditions.

Metabolic Contributions of Microbiome

• Butyrate and Gut Health

  • Short-chain fatty acids (SCFAs), especially butyrate, are critical for gut epithelial health and maintaining tight junctions.

  • Healthy microbiomes produce SCFAs, contributing to nutrient absorption and gut integrity.

• Germ-Free Mouse Studies

  • Germ-free mice can be colonized to mimic human microbiomes, providing insights into metabolism and obesity.

Dysbiosis and Health Implications

• Consequences of Dysbiosis

  • Weak junctions and lack of SCFAs lead to conditions like leaky gut and chronic inflammation.

  • Dysbiosis is linked to various diseases, highlighting the importance of microbial diversity for health.