Microorganisms in and on Us

The microbiome refers to the entire community of microorganisms that inhabit the human body, both internally and externally.

The gut microbiome plays several crucial roles:
- Digestion of Compounds: Assists in breaking down nutrients that human enzymes alone cannot digest.
- Synthesis of Compounds: Microorganisms synthesize vitamins such as Folate, Vitamin K, and Biotin.
- Protection Against Pathogenic Microorganisms: It serves as a barrier, preventing harmful microbes from proliferating.
Variability: The gut microbiome differs significantly among individuals, leading to diverse health outcomes.

Investigations into historical microbiomes reveal similarities with the gut microbiomes of non-industrialized societies, suggesting significant divergence in industrialized populations due to lifestyle and dietary changes.

The skin hosts a diverse array of bacteria that vary significantly from one microenvironment to another, akin to different ecosystems (jungles and deserts).
North Carolina Navel Project: Studied 60 navels and found over 2000 bacterial species, demonstrating the diversity of skin microbiomes.

The oral microbiome comprises various bacteria such as Streptococcus species, which play critical roles in oral health. Variations can occur due to diet, hygiene, and other factors.

Global efforts to catalog urban microbiomes reveal unique microbial fingerprints for cities, with variations influenced by geography and population density.

Biofilms are aggregates of microorganisms attached to surfaces, forming a protective matrix. These structures can lead to chronic infections and are found on various surfaces, including medical devices.

The gut microbiome may contribute to obesity; specific compositions may allow for greater energy extraction from the diet.
Statistics: Estimates suggest that there are about 10,000 species within human-associated microbiomes, yielding approximately 20 million microbial protein-coding genes compared to roughly 23,000 human genes.

Certain diseases have been linked to significant changes in the human microbiome:
- Asthma: Increased airway microbial diversity; correlations exist with bronchial hyperresponsiveness.
- Colorectal Cancer: Tumors enriched in typical gut microbes relative to surrounding healthy tissues.
- Kidney Stones: Lack of specific bacteria associated with oxalate metabolism increases risk.

Alterations occur with dietary changes, lifestyle modifications, and even with immigration. For example, diets rich in starch versus proteins significantly influence gut microbiota composition.
A high protein diet leads to observable changes in gut bacteria.

The skin acts as an ecosystem featuring varied topographies and microenvironments. Bacteria in this niche exhibit distinctive compositions based on the area of the skin sampled.

DNA sequencing, particularly of the 16S ribosomal RNA, has become critical in cataloging and understanding the microbiome's complexities. The Human Microbiome Project is a significant effort towards this end, encompassing thousands of samples from diverse populations.

The research suggests that therapeutic interventions targeting the microbiome could provide alternative routes for addressing health issues and restoring microbial diversity.
Probiotics and fecal transplants are explored as methods to restore healthy microbiota.

The human microbiome is an essential and dynamic ecosystem influencing various aspects of health through its interactions with human physiology. Understanding and potentially manipulating these microbial communities could hold the key to innovative health solutions.