Microbiomes: Each of Us is an Ecological System

In the future we'll manage our microbiomes that way organic farmers grow crops, helping good species to  flourish while making life harder for the undesirable ones.

Kellyn Betts has an article in Environmental Health Perspectives this month about something that hasn't recieved a lot attention in the health policy and health delivery sectors yet, but certainly will do soon. It's the microbiome. Her article A Study in Balance: How Microbiomes Are Changing the Shape of Environmental Health shows why this is an emerging field of research that has so many people excited.

For those not familiar with the term, microbiomes are the tiny ecosystems of microbes and other little critters that live on and in each of us. There are an estimated 100 trillion microbes now going about their business in four major biomes: the mouth and gastrointestinal tracts, the respiratory system, the urogenital systems and the skin.  Microbes are so important to our ability to function that microbiologists are proposing to call us all "superorganisms," that is, symbiants of us and our bacteria. There has been so much interest in the microbiome that the National Institute of Health has set up the Human Microbiome Project to study them.  We all learned in high school that microorganisms break down complex carbohydrates and help us to digest our Cheerios, but systems biologists are just now starting to unwind the much more complex ways that these organisms keep us going. Early results indicate that bacteria affect the way some toxins are introduced into our systems. Other studies now in the pipeline are looking at how disturbances in our intestinal biomes may be implicated in diseases such as acne, Crohn's disease, and obesity.



So how will an understanding of microbiomes change the way medical care is delivered?  Well, they say guessing about the future is hazardous but the most immediate implication is that it we will change the way we think about antibiotics.  Killing the harmful bacteria will only be half the battle.  To get patients back to full health we will need to restore their microbiomes to functioning order.  In the future we'll manage our microbiomes that way organic farmers grow crops, helping good species to  flourish while making life harder for the undesirable ones.  To understand why, it is helpful to bring in some insights from the macro-environmental sciences.

Disturbance theory was developed to describe how large-scale environmental systems like forests and coral reefs respond to events such as fires or hurricanes.  A healthy ecosystem with plenty of diversity among its species will regenerate after a disturbance and all will be well.  The problems start when disturbances get compounded, dynamite fishing on the reef in addition to a hurricane, for instance.  The natural process of renewal becomes degraded and the system becomes vulnerable to invasive species.  Invasive species are opportunists that can thrive on undefended real estate.  If we are lucky the invaders will be fairly benign but sometimes they are not.  Ciguatera poisoning is caused by one such opportunist, Gambiadiscus toxicus.  Like a number of algae species it has the ability to produce a potent neurotoxin.  Disturbed coral reefs provide G. toxicus with havens in which to multiply and be eaten by the local fish.  When humans fish the contaminated reefs they too consume the toxin.  For the unlucky diner Ciguatera poisoning can result in nerve damage and even death.

Knowledge of how such large-scale ecological systems work can only aid us to better manage our internal ecosystems, but it requires a new way of thinking in medicine.  Researchers are already beginning to think about us as environments on legs.  That mental shift, seeing ourselves not as discrete units but as beings in constant interaction with our surroundings will continue to be the focus of Total Health Environment.