​​​​​​​Microbiome

1. Definition

The microbiome refers to the entire community of microorganisms (bacteria, viruses, fungi, archaea, and protozoa) living in a specific environment, particularly on or inside the human body. It includes their genetic material, interactions, and functions.

2. Origin of the Human Microbiome

• Initial colonization:
  Humans begin acquiring their microbiome immediately after birth. During vaginal delivery, babies are exposed to the mother’s vaginal and intestinal microbes, which seed their own microbiome. Cesarean section births tend to expose newborns to different microbes, often from the skin or environment.

• Early life development:
  The infant microbiome rapidly develops in the first few years of life, influenced by diet (breast milk vs formula), environment, antibiotics, and hygiene.

• Maternal influence:
  The mother’s microbiome, health, diet, and even mode of birth significantly influence the infant’s microbial colonization and long-term health.

• Microbiome maturation:
  By age 3, the human microbiome generally stabilizes and resembles an adult-like composition, though it can change with diet, illness, and lifestyle.

3. Development Over a Lifetime

• The microbiome continues to evolve throughout life based on diet, environment, antibiotic use, illness, stress, and aging.

• The gut microbiome is the most studied, with trillions of microbes playing key roles in digestion, nutrient absorption, immune modulation, and protecting against pathogens.

• Other body sites with distinct microbiomes include the skin, mouth, respiratory tract, urogenital tract, and even the placenta.

• Aging is associated with changes in microbiome diversity, which can impact health, inflammation, and disease susceptibility.

4. Functions and Importance

• Digestion: Breaks down complex carbohydrates, produces vitamins (like B and K), and assists in nutrient absorption.

• Immune system: Trains and modulates the immune system, helps prevent infections by outcompeting harmful microbes.

• Metabolism: Influences body weight, fat storage, and metabolic health.

• Protection: Provides a barrier against pathogens through competitive exclusion and production of antimicrobial compounds.

• Brain-Gut axis: Emerging research shows the microbiome influences mental health, mood, and neurological functions through biochemical signaling.

5. Microbiome Imbalance (Dysbiosis)

• Dysbiosis refers to an unhealthy imbalance in the microbial community.

• Linked to many conditions: inflammatory bowel disease, obesity, allergies, asthma, diabetes, depression, and autoimmune diseases.

• Antibiotic use, poor diet, infections, and chronic stress can contribute to dysbiosis.

6. Research and Applications

• Advances in DNA sequencing and metagenomics have revolutionized microbiome research.

• Therapeutic approaches: probiotics, prebiotics, synbiotics, and fecal microbiota transplantation (FMT).

• Personalized medicine aims to manipulate the microbiome to treat or prevent disease.

• The microbiome is a frontier in understanding human health and disease beyond genetics alone.

7. Interesting Facts

• The microbiome contains approximately 100 trillion microbial cells — roughly equal to or exceeding human cells in the body.

• The combined genome of the microbiome (microbiome genes) is about 100 times larger than the human genome.

• Each person has a unique microbiome signature, often called a “microbial fingerprint.”