A recent short report on NPR and an article on the possibility of a microbial basis for some types of obesity both comment on the number of cells in the human body as well as the numbers of our microbial passengers. The amounts are surprising. There are 100 trillion, (10 to the 14) cells in the human body, but we carry 10 to 20 times more microbes than that. It seems we are more them than us (or me). If that doesn't start the itching and turn you into a recluse a la Howard Hughes I don't know what will.
The science fiction story "Blood Music" by Greg Bear (eventually lengthened into a novel) relates the story of a scientist who creates biological computers which then go on to take over his body and potentially the world. From the microbial perspective, they already own the world and use us as hotels, they don't really need to take over.
tags: microbes, Greg Bear