AOBiome - The Human Microbiome

The Human Microbiome

A Brief Introduction
Our most complex system may well be the microbiome. It consists of hundreds of trillions of microorganisms, outnumbering human cells by 10 to 1, with as many as 3 million bacterial genes to our 23,000. While the microbiome has recently become an area of active research, its overall effects on human health remain largely unknown.

Human microbiome bacteria were among the first ones ever described by Antony van Leeuwenhoek, who discovered them in a sample of his saliva in 1683. Despite that, until recently the studies of human bacteria have been almost exclusively focused on pathogens (harmful kinds of bacteria). This has led to many advances in medicine and public health, including sterilization and sanitation, antimicrobial drugs, vaccines, etc. but at a cost of largely ignoring a vast number of other beneficial microorganisms that critically affect human health.

Our microbiome mostly consists of commensal organisms that only can become pathogenic if the host is severely immunocompromised. It actually exerts a limiting effect on growth of other microorganisms, including pathogens, due in part to low pH resulting from aerobic lactic acid fermentation. The commensal bacteria also disrupt the pathogens' quorum sensing mechanisms. Other beneficial functions of the microbiome include vitamin K processing amd breaking down complex carbohydrates, increasing their bioavailability.

The microbiome is not static - it is the dynamic product of the competition of diverse microorganisms, further influenced by human physiology and individual conditions. For example, bacteria adjust production of vitamins in the gut according to the our nutritional needs.

If the natural commensal bacteria are eliminated by antibiotics or other means, they no longer suppress potential pathogens, which is why fungal and secondary bacterial infections sometimes follow an antibiotic treatment. These fast-growing "weeds" of the microbiome can be notoriously difficult to fight. Clostridium difficile, for example, causes life-threatening gut infections in people who have been taking antibiotics, killing 14,000 people per year in the US.

When natural bacteria are reintroduced by a simple transplant of gut flora from a healthy individual, the Clostridium infection is often resolved. This illustrates that maintaining a balanced microbiome safeguards human health.

AOBiome agrees with that philosophy, focusing on the largest organ in the human body that nourishes a large and diverse community of bacteria - our skin.