Key Concepts on Human Microbiome

What It Means to Be Human

• Human composition is majorly non-human, consisting of microbial cells.
• Humans are said to be 10 parts microbe and 1 part human based on microbial cell count.
• In terms of unique genes, humans are only 1% human and mostly bacteria.

Human Microbiome

• Definition: The microbiome is a set of microbial communities that have co-evolved with humans.
• Function: Provides essential functions humans cannot perform, such as:
  • Digestion of complex polysaccharides from plants.
  • Protection against harmful microbes through colonization resistance.

Location of Microbes

• Predominant Location: Most microbes are located in the bowel.
• Other Locations: Mouth and various other body parts exposed to the external world.

Importance of Microbiome

• Nutrient Recirculation: Assists in nutrient recirculation and maintaining cholesterol levels.
• Infection Shield: Provides an internal shield against invasive harmful microbes.

Impact of Antibiotics

• Negative Effects: Antibiotics can severely impact microbial communities.
• Recovery in Healthy Individuals: Microbiome often recovers well in healthy individuals.
• Risks in Sick Individuals: Weakened individuals may face severe risks, such as infections by Clostridium difficile.

Probiotics as a Potential Solution

• Suggested to restore friendly bacteria.
• Early evidence suggests potential benefits, but findings are still inconclusive.

Health Implications

• Potential links between microbiome damage due to antibiotic overuse and diseases like heart disease and cancer remain unexplored.

Shift in Perception

• Historical view: Bacteria seen mainly as harmful.
• Current understanding: Acknowledging the vital role of beneficial microbes which make up 99% of our biological identity.