You may have seen or heard the recent headlines, along the
lines of "Women's Hands 'Germier' than Men's." The report behind the rather misleading
news flash is more interesting.
University of Colorado professor Noah Fierer studies the
ecology of bacteria, fungi, and related microbes in natural systems such as
soil, water, and the atmosphere. Turning his survey techniques to the human
body, he looked at the diversity of bacteria on the hands of 51 students--all
healthy except for the interesting twist that they'd all just finished their
final exams. (Sweatier palms than usual, perhaps?)
Fierer and his colleagues used a gene-sequencing technique
to count the number of different types of bacteria on each subject's hands. They
tallied an impressive 4,742 types.
The quirky news headlines jumped out of the unexpected
finding that the hands of female students harbored a greater diversity (but not
necessarily more germs, per se) than did the guys'.
Just as interesting, perhaps, was the finding that while
everyone seemed to share a core group of common skin bacteria, these common species
made up just 13 percent of the total diversity. In fact, over 80 percent of the
microbial species found on a person's left hand were different from those found
on the right.
All this seems to suggest that most of the bacteria on our hands are
fleeting transients. We pick them up as we touch objects, surfaces, and other
body parts.
That said, the researchers found that hand washing--while a
good idea when you're around others who might be ill--did little to change the
diversity of the a palm's rainforest-rich ecosystem.
Hre's the study, in the Proceedings of the National
Academy of Sciences, with more interesting stuff at Fierer's website at the
University of Colorado.
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