Gut check? Part of the 21st century vernacular. Look it up on dictionary.com and you’ll find this definition: a pause to assess the state, progress, or condition of something such as an enterprise or institution.
Look around you! Do you live in the European Union, teetering on the brink of a financial crisis? Time for a gut check. In India, where the growth rates of recent years that have propelled the country’s improved economy are slowly eroding as the result of corruption and governmental complacency? Time for a gut check. In China, where the transition to superpower status, maybe even global supremacy, seems tantalizingly close, but where a rapidly aging population, flawed market and political mechanisms, and environmental deterioration threaten your future? Time for a gut check. In America, where bitterly partisan politics distract and delay attention to pressing common needs to improve the economy, education, and health care? Time for a gut check. Are you a basketball player on the Oklahoma Thunder, down two games to one to the Miami Heat in the NBA playoffs? Time for a gut check. Do you work for NOAA, with its myriad fiscal, managerial, and technological challenges? Time for a gut check.
Or for that matter, look inside your individual self. Maybe you and I could profit from a gut check as well.
That’s just what the journal Science has done in its 8 June 2012 issue, which is devoted to new science on the gut microbiota. As Princeton molecular biologist Bonnie Bassler reminds us, on her much-viewed TED talk, our human bodies contain about a trillion cells, but ten times as many separate, distinct microbial cells live in us or on us at any given time. We have about 30,000 human genes; those bacteria have about one hundred times as many genes. So we’re not humans so much as colonies of microbes. [Don’t worry! No need to experience vertigo, or feel disembodied; those microbial cells are much smaller than our own. Maybe they amount to a few pounds of our body mass.]
Now as scientists are coming to find out, and the dozen or so articles in Science emphasize, these bacteria are not passive riders. Anything but! They have been, and continue to be, crucial “for our evolution, development, metabolism, immune defense, and susceptibility to a multiplicity of infectious and noncommunicable diseases.” One article tells us that microbiome imbalances have been implicated “in disorders as diverse as cancer, obesity, inflammatory bowel disease, psoriasis, asthma, and possibly even autism.” [Here’s a factoid to illustrate for you and me: 36% of the small molecules found in our human blood are contributed by the human gut biome.]
Whew! That can make us all seem so fragile. But the fact of the matter is, it’s all rather robust. You and I are obviously far healthier and more long-lived because we work this way. And the future for medicine looks bright. Scientists are busy exploring how all these thousands of species within us interact and cooperate to maintain us and keep us healthy and on the go. They’re learning how and why these finely-tuned relationships occasionally break down, and what that means for us. They’re developing new disease therapies based on this knowledge and understanding.
Ecologists in particular are having a field day. Just read this abstract from an article in this special issue of Science, entitled The Application of Ecological Theory Toward an Understanding of the Human Microbiome, by Elizabeth Costello, Keaton Stagaman, Les Dethlefsen, Brendan Bohannon, and David Relman: The human-microbial ecosystem plays a variety of important roles in human health and disease. Each person can be viewed as an island-like “patch” of habitat occupied by microbial assemblages formed by the fundamental processes of community ecology: dispersal, local diversification, environmental selection, and ecological drift. Community assembly theory, and metacommunity theory in particular, provides a framework for understanding the ecological dynamics of the human microbiome, such as compositional variability within and between hosts. We explore three core scenarios of human microbiome assembly: development in infants, representing assembly in previously unoccupied habitats; recovery from antibiotics, representing assembly after disturbance; and invasion by pathogens, representing assembly in the context of invasive species. Judicious application of ecological theory may lead to improved strategies for restoring and maintaining the microbiota and the crucial health-associated ecosystem services that it provides.
A couple of thoughts prompted by this read . First, it’s easy to conjecture that the history that brought us to today wasn’t smooth…that the normal biota of today were each, successively, the invasive species of yesterday, that their initial invasions into humans brought disease, illness, death, and adaptation and natural selection before both bacterium and human host settled down and established a “new normal” for both bacterium and human host. [All those alien sci-fi movies that are part of our summertime viewing? Those alien encounters and those battles are being waged inside us all along.]
Second, at this bacterial level, the range of diversity is far greater than the ethnic- and other types of diversity that we seem to find so problematic and insurmountable at the human level. Those people we find so unlike us, who grate on our every nerve? Internally, our biomes are handling far more profound differences, preferences, and agendas with ease…in fact, using these to develop and maintain a harmonious whole.
Which brings us to the last individual gut check. Your spirit and demeanor. And mine. How is our spirit? Can we look at each other and understand that we’re all in it together? That what diminishes you diminishes me, and vice versa? That what builds you up doesn’t come at my expense but in fact enhances my options and prospects? Our respective biomes model that for us every day.