The Superorganism Revolution
The bacteria living on and in us are challenging paradigms in community ecology.
In 1676, Antoni van Leeuwenhoek—a Dutch draper and amateur naturalist—peered through a microscope of his own design and described a world that would be misunderstood for the next 300 years. What he saw resulted in the first known description of bacteria, which “were…so small…that if 100 of them lay one by another, they would not equal the length of a grain of course [sic] Sand.” But contemporary scientists had a hard time believing they were real.
After submitting his account to the Royal Society of London, that illustrious body’s reply belongs in the annals of rejection letters perhaps better left unwritten:
Your account of myriad “little animals” seen swimming in rainwater, with the aid of your so-called “microscope,” caused the members of the society considerable merriment…. Your novel descriptions of the sundry anatomies and occupations of these invisible creatures led one member to imagine that your “rainwater” might have contained an ample portion of distilled spirits—imbibed by the investigator…. a vote having been taken among the members—accompanied I regret to inform you, by considerable giggling—it has been decided not to publish your communication in the Proceedings of this esteemed society. However, all here wish your “little animals” health, prodigality and good husbandry by their ingenious “discoverer.”
The existence of a living world beyond the reach of our senses is no longer controversial, but the medical profession’s attitude toward our bacterial associates has, until recently, oscillated between benign neglect and suspicious distrust. The bacteria in our bodies were considered, at best, largely incidental to our existence, or at worst, pathogens in the making. Either way, bacteria were something apart that could be ignored or, if necessary, exterminated. Only now, 350 years after van Leeuwenhoek’s discovery, science is giving microbes their due as vital, complex parts of the human ecosystem. Propelled, as van Leeuwenhoek had been, by a set of technological breakthroughs—the ability to identify our bacterial partners using DNA sequencing—we are beginning to understand just how deeply our biological identity depends on them.
Science is just starting to grasp the sheer abundance and diversity of bacterial life present on and in our bodies. More important, we realize that these bacteria are not simply squatters or unavoidable hitchhikers picked up as we move through a world crowded with microbes. Rather, they influence our health, digestion, metabolism, and response to medicines, not to mention our survival and evolution. The discovery of the human microbiome, the collection of microbial ecosystems that colonize virtually every external and internal body surface, has forever changed how we see ourselves. These bacteria shape our biology from birth to the grave. They are part of us.