Human Microbiome and Normal Flora of Human Body

Summary

The human microbiome is a vast ecosystem of microorganisms living inside and on the human body, playing crucial roles in health. It includes bacteria, fungi, viruses, and other microbes, with bacteria being the most abundant. These microorganisms support digestion, immunity, and protect against harmful pathogens. The microbiome varies across body regions, such as the skin, gut, and respiratory tract, and is influenced by factors like diet, age, and antibiotics. Disruptions to this microbial balance can lead to diseases. Maintaining a healthy microbiome is essential for overall well-being, with probiotics and prebiotics offering ways to support it.

Takeaways

• 😀 The human microbiome consists of trillions of microorganisms, including bacteria, fungi, viruses, and other microbes, which play crucial roles in human health.
• 😀 Microbial cells in the human body outnumber human cells by a ratio of about 10:1 and collectively weigh around 2 kg, similar to the weight of the human brain.
• 😀 The microbiome is distributed across different parts of the body, including the skin, oral cavity, respiratory tract, gut, and vaginal and urinary areas, each hosting distinct microbial communities.
• 😀 Resident flora are permanent inhabitants of the body, providing long-term health benefits like preventing pathogen colonization, while transient flora are temporary visitors with fluctuating populations.
• 😀 The skin microbiome is influenced by factors such as moisture, pH, sebum production, and temperature, and includes key bacteria like *Staphylococcus epidermidis* and *Propionibacteria*.
• 😀 The oral microbiome is one of the most diverse microbial communities in the body, with bacteria like *Streptococcus mutans* forming dental plaque, while the respiratory tract has a gradient of microbial colonization.
• 😀 The gut microbiome varies significantly along the digestive tract, with the small intestine hosting fewer microbes focused on nutrient absorption, while the large intestine has a higher microbial density focused on fermentation and metabolic regulation.
• 😀 The vaginal microbiome, primarily composed of *Lactobacillus* species, helps maintain a healthy pH and prevent pathogen growth, while the urinary tract remains sterile due to regular urine flow.
• 😀 Factors like age, diet, hygiene, antibiotic use, and genetics influence the composition and diversity of our microbiomes, shaping our unique microbial fingerprint over time.
• 😀 Dysbiosis, or microbial imbalance, can lead to diseases such as urinary tract infections, dental carries, and gut infections like *Clostridium difficile*, highlighting the importance of maintaining a balanced microbiome.
• 😀 Probiotics, prebiotics, and fecal microbiota transplantation (FMT) are emerging as promising methods to restore or maintain a healthy microbiome, with potential applications in treating various health conditions.

Q & A

What is the human microbiome?

The human microbiome refers to the collection of trillions of microorganisms, including bacteria, fungi, viruses, and other microbes, that live on and inside the human body. These microbes play crucial roles in digestion, immune function, and protection from harmful pathogens.

How do resident and transient flora differ?

Resident flora are permanent inhabitants of the body that are well adapted to specific locations, providing long-term benefits such as preventing pathogen colonization and supporting immune function. Transient flora are temporary visitors, whose populations fluctuate and may be beneficial, neutral, or potentially harmful depending on circumstances.

What role do bacteria like *Staphylococcus epidermidis* and *Corynebacteria* play on the skin?

*Staphylococcus epidermidis* is the most abundant bacterium on the skin, helping to maintain skin health. *Corynebacteria* thrive in moist areas such as the armpits and groin, contributing to body odor through their metabolic activities.

What is the primary function of the gut microbiome?

The gut microbiome, particularly in the large intestine, plays a vital role in breaking down complex carbohydrates that human digestive enzymes cannot process. These microbes produce short-chain fatty acids like butyrate, acetate, and propionate, which nourish intestinal cells and regulate metabolism.

How does diet influence the gut microbiome?

Diet strongly impacts the gut microbiome composition. A plant-based diet rich in fiber promotes beneficial bacteria like *Bacteroides* and *Bifidobacteria*, while high-protein diets tend to favor bacteria from the *Proteobacteria* group.

What happens to the microbiome during antibiotic treatment?

Antibiotics can disrupt the balance of the microbiome by significantly reducing both harmful and beneficial bacteria. In the recovery phase, beneficial bacteria begin to repopulate, but the new microbial balance may differ from the original state.

What is dysbiosis, and how does it affect health?

Dysbiosis refers to an imbalance in the microbiome, where potentially harmful microbes overgrow. This can happen due to factors like antibiotic use, diet changes, or stress. Dysbiosis can contribute to various health issues, such as infections, inflammation, and gastrointestinal disorders.

What is fecal microbiota transplantation (FMT), and when is it used?

Fecal microbiota transplantation (FMT) is a medical procedure that involves transferring fecal matter from a healthy donor to a patient to restore a balanced gut microbiome. FMT is primarily used to treat recurrent *Clostridium difficile* infections with high success rates.

How does the vaginal microbiome contribute to women's health?

The vaginal microbiome, primarily composed of *Lactobacillus* species, maintains an acidic pH (3.8 to 4.5) that helps prevent the growth of pathogenic bacteria. It also adapts to changes during the menstrual cycle and pregnancy while providing a protective barrier against infections.

What factors influence the composition of the human microbiome?

Several factors shape the microbiome, including age, diet, antibiotics, immune system status, hygiene practices, and environmental exposures. These elements continuously influence which microbes thrive or decline throughout a person's life.