What Is the Microbiome?

You Are Never Alone

Right now, trillions of microorganisms are living on and inside your body. They're on your skin, in your mouth, up your nose, and especially in your gut. Together, this community of bacteria, archaea, fungi, viruses, and other microbes is called your microbiome.

In fact, you have about as many microbial cells as human cells — roughly 38 trillion of each! And the genetic diversity is even more striking: while you have about 20,000 human genes, your microbiome contains 2-20 million unique genes. In a very real sense, you're a walking ecosystem.

Microbiome vs. Microbiota

You might hear these terms used interchangeably, but they have slightly different meanings:

• Microbiota: The actual community of microorganisms living in a particular environment (like your gut)
• Microbiome: The microbiota plus all their genes, proteins, and metabolic products — the whole "theater of operations"

The Gut Microbiome: Your Inner Rainforest

Your gut (particularly the large intestine) houses the most diverse microbial ecosystem in your body. It contains hundreds of different species, with the exact composition being unique to you — as individual as your fingerprint.

The major players include:

• Bacteroidetes and Firmicutes: The two dominant bacterial phyla, making up about 90% of gut bacteria
• Bifidobacteria: Beneficial bacteria that help digest dietary fiber
• Lactobacilli: Famous probiotics that produce lactic acid
• Archaea: Methane-producing microbes that help process indigestible foods

What Does Your Microbiome Do For You?

Your microbiome isn't just along for the ride — it performs vital functions:

• Digestion: Gut bacteria break down fiber and other compounds your own enzymes can't handle, extracting extra calories and nutrients from your food
• Vitamin production: Bacteria synthesize vitamins K, B12, biotin, and folate that your body needs
• Immune training: Your microbiome teaches your immune system to distinguish friend from foe, helping prevent allergies and autoimmune diseases
• Pathogen defense: Good bacteria compete with harmful ones for space and nutrients, keeping you healthy
• Brain communication: The gut-brain axis allows your microbiome to influence mood, behavior, and even cognition through hormones and nerve signals

How Your Microbiome Forms

Your microbial journey begins at birth:

• Babies born vaginally are coated with their mother's vaginal and gut bacteria
• C-section babies get more skin bacteria initially
• Breastfeeding further shapes the infant microbiome with beneficial bacteria and prebiotics
• By age 2-3, your microbiome is mostly stable and adult-like

What Affects Your Microbiome?

Many factors influence your microbial community:

• Diet: The biggest factor! Fiber feeds beneficial bacteria, while processed foods may favor less helpful species
• Antibiotics: Can dramatically disrupt your microbiome, sometimes with lasting effects
• Environment: Where you live, your pets, and your exposure to nature all matter
• Stress and sleep: Your mental state affects your gut bacteria, and vice versa
• Age: Microbiome diversity tends to decrease as we get older

The Future of Microbiome Science

Scientists are still uncovering the mysteries of the microbiome. Current research explores:

• How the microbiome influences conditions from obesity to depression
• Fecal microbiota transplants (FMT) to treat certain diseases
• Personalized probiotics tailored to your unique microbiome
• The role of the microbiome in cancer treatment response

Understanding your microbiome opens doors to treating diseases we never before connected to our microbial passengers. The more we learn, the more we realize that taking care of our microbes means taking care of ourselves.