Tim Radford at The Guardian:
We are not alone. We have never been alone. We are possessed. Our inner demons cannot be cast out, because they did not move in and take possession: they were here before us, and will live on after us. They are invisible, insidious and exist in overwhelming numbers. They manage us in myriad ways: deliver our minerals and vitamins, help digest our lunch, and provide in different ways all our cheese, yoghurt, beer, wine, bread, bacon and beef. Microbes can affect our mood, take charge of our immune system, protect us from disease, make us ill, kill us and then decompose us.
As complex, multicellular lifeforms, we are their sock puppets. We spread them, introduce variety into their brief lives and provide them with all they need to replicate and colonise new habitats. We are perambulating tower blocks, each occupied by maybe 40tn tiny tenants. Our skins are smeared with a thin film of microbial life, with ever greater numbers occupying every orifice and employed in colossal numbers in our guts.
Yet, until late in human history, we didn’t know they were there at all. We still do not know who they all are, or what they do. We discover new things almost every day.