For every human cell in your body, there are ten bacterial cells living on or in it. So it's an open question whether "you" are a primarily human individual or a walking soil patch for an ecosystem of interacting microbes. But even if the latter turns out to be the case, it may be of some comfort to learn that "you" in all your plurality are nevertheless unique.
A recent University of Colorado-Boulder study has found that, based on a swab-and-sequence search of 27 bodily niches (from forehead to the soles of the feet) of nine subjects, the germs we carry vary substantially in composition from person to person. (As a one-time student at that university, I can testify to having witnessed my share of filthy feet and, around final exam time, a case or two of forehead film -- but that's college life for you.)
The study builds on work by, for example, Stanford's David Relman and colleagues, published earlier this year, that used state-of-the-art gene-sequencing technology to identify thousands of distinct bacterial strains within the gut of each individual examined. There, too, much inter-individual variation was observed, as well as a fair amount of within-individual change over time -- and, importantly, distinct disruptions of intestinal microbial communities when certain antibiotics formerly thought to be relatively inactive in the gut were ingested.
Fortunately, those internal microbial communities did come back to a reasonable semblance of their original compositions within a month. But if "you" (singular) are actually "you" (plural) -- an entire ecosystem in which the human component is vastly outnumbered by the prokaryotic population -- it's a bit disconcerting to consider that you could undergo a subtle personality change every time you blow your nose.
