Microbes – from our guts to the great coral reefs


Recall that every individual animal, whether human or coral, is an ecosystem in itself. It grew up under the influence of its microbes and continues to engage them in a lively negotiation. Remember also that these partners often have competing interests and that hosts need to control their microbes, keeping them in line by offering the right food, confining them to specific tissues, or placing them under immune surveillance. Now imagine that something disrupts that control. It jostles the micro biome, changing the proportions of species within it, the genes they activate, and the chemicals they produce. This altered community still communicates with its host, but the tenor of their conversation changes. Sometimes it becomes, quite literally, inflammatory, as microbes over stimulate the immune system or wheedle their way into tissues where they don’t belong. In other cases, microbes might start to opportunistically infect their hosts. That’s dysbiosis.

Its not about individuals failing to repel pathogens, but about breakdowns in communication between different species – host and symbiont – that live together. It is disease, recast as an ecological problem. Healthy individuals are like virgin rainforests or lush grasslands or Kingman Reef. Sick individuals are like fallow fields or scum covered lakes or the bleached reefs of Christmas Island – ecosystems in disarray. This is a more complicated view of health, and one that raises important questions. Foremost among them: Are such changes the cause of disease or merely its consequence? 



excerpt from


by Ed Yong

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