We will probably never know their names, but the contribution of 242 American men and women who were willing to share the intimate details of their microbial profile with the world is having a profound impact on our understanding of health and illness, and is even raising questions about what it means to be human. Research into the microbiome -- the viruses, bacteria and other microbes living with us -- also puts a whole new slant on some long-standing public health problems, like the overuse of antibiotics. But more on that later.

In June last year, after five years of work by around 200 scientists from 80 universities, the US-based Human Microbiome Project released the initial analyses of blood, stool and saliva samples, as well as swabs taken from various locations on the volunteers' bodies. The results paint an extraordinary, though preliminary, portrait of the richness of our microbial life. The researchers found over 10,000 species of microbes living in and on their subjects, with each person carrying about 8 million different bacterial genes (compared with 22,000 or so human genes). They described their findings as "the largest and most comprehensive reference set of human microbiome data associated with healthy adult individuals".