Tuesday, October 1, 2013


 Mushrooms and moss, Tallman State Park, New York
 photograph by the author

Everything that you can see is supported by things you can't.

When Antonie van Leeuwenhoek —  the world's first microbiologist — first peered through the lenses of his microscopes in Delft, he revolutionized the world in a way that his contemporary, Johannes Vermeer, also did — he saw things in a new way. What he saw, however, had much more profound and exciting implications than anything Vermeer was able to observe on the macroscopic scale.

In van Leeuwenhoek's time, it was fundamentally impossible to appreciate just what this extraordinary "new" world of microbes meant. Initial investigation was largely a matter of cataloging. It hasn't been, in fact, until the 21st century, with the advent of DNA analysis, that we begin to know microbiology at the extraordinary level of detail that it's necessary to have in order to understand what is going on. This linked article about the understanding of what gut bacteria are doing in termites is an example of exactly what I mean by this.

 The bottom line is that microbes appeared to be novelties, zoological specimens for aesthetic appreciation, for the first few centuries we knew about them. It was only when it became understood that they cause disease ( see the germ theory of disease), which took place only in the 19th century —! — that human beings outside the immediate scientific community of microbiologists (who up until then had been considered, no doubt, a small community of obsessive cranks engaged in pointedly pointless studies) began to take a much more active interest in these communities in order to understand just what they meant to us. We began to see that microbes have a huge impact on us.

Plague diseases like the bubonic plague and cholera are specifically caused by bacteria; not only do they wipe huge swathes of human population out, they have, as William Hardy McNeill pointed out in 1976, major impacts on world history. The strange and under-appreciated fact is that who we are — our societies, governments, cultures, and history — has been determined to a significant extent by the microbes we share the globe with. People don't think about this in their day-to-day life, but if a plague breaks out — it's all they think about.

 The underpinnings of human culture and society are determined to an even greater extent by microbes, whose action in society is not limited to disease alone. Fungi such as Amanita Muscaria and psilocybin have influenced religious practices for thousands of years; the Mediterranean practice of fermentation of milk into cheeses through the action of bacteria has had a major worldwide impact on food culture; and other forms of fermentation are equally important in other cultures. Perhaps the most important and pervasive type of fermentation is the production and distillation of alcohol; this process is dependent on yeast microorganisms.

What this means is that no matter what you do, and no matter where you are, on a daily basis, you are interacting with foods and beverages that depend on microbiotic communities for their very existence. Disruptions to the microbial communities which make these processes possible would spell, perhaps, the end of the processes themselves. It may seem alarmist to suggest that invasive bacteria could create situations where something this drastic takes place, but the possibility is certainly there.

More important, perhaps, than the fact that microbes and their activity pervade our food culture is the fact that they live on us; and they live not only on us, but in us. The sheer number of microbes living in any human body is staggering, numbering in the trillions. There are thousands, and probably tens of thousands, of different species of bacteria inhabiting every human body; from their point of view, we are their ecosystem, their habitat. Habitat and ecosystem, you see, are a matter of scale: from our point of view, we live in the jungle, or the desert; from a microbe's point of view, it lives in the gut, or on the skin. The analogies are apt; the gut is dark and moist, with a rich and diverse community of microbes, like a rain forest; the skin is relatively dry and has a much smaller population, like a desert.

 We'll talk about this more in the next post.

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