Microbial Diversity Week 1

Microbial Diversity

• Estimated microbial species on Earth could be as high as 10^12.
• Human body comprises roughly 10^13 human cells to 10^14 microbial cells.

Microbiota vs. Microbiome

• Microbiota refers to the total microbial population in a specific habitat (e.g., gastrointestinal microbiota).
• Microbiome encompasses the genetic content of the microbiota.

Influencing Factors

• Microbial composition affected by pH levels, water availability, nutritional content, and oxygen levels.

Human Microbiota and Health

• Microbiota communicate bidirectionally with the gut-brain axis, impacting metabolism, gastrointestinal homeostasis, appetite regulation, stress, anxiety, and memory.
• Gut-brain axis helps stimulate immune response, aiding normal immune system development.
• Microbiota increase metabolic capabilities and serve as a physical barrier against pathogens by competing for resources and producing antimicrobial substances.

Symbiotic Relationships

• Mutualism: Two organisms benefit from each other (e.g., gut bacteria metabolizing undigested carbohydrates, enhancing nutrient availability).
• Commensalism: One organism benefits while the other is unaffected (e.g., oral microbiota utilizing sugars without impacting human health).
• Relationship can shift to disease state with environmental changes (e.g., dietary changes).
• Parasitism: One organism benefits at the host's expense, often transforming symbiotic microbiota into harmful parasites under conditions of dysbiosis.

Microbiota Locations

• Skin: Acts as a mechanical barrier to infection, inhospitable to many microbes due to low moisture, high salt concentration, and acidity.
• Mouth: Home to complex microbial communities, including 500-600 bacteria types, primarily anaerobes.
• Oral cavity serves as an entry point for pathogens targeting the upper respiratory tract.