[at-l] Healthy Trail Hygiene: leave the Purell at home......
sloetoe at yahoo.com
Tue Feb 6 10:19:27 CST 2007
Human skin populated by veritable zoo of bacteria
By Will Dunham
Mon Feb 5, 5:06 PM ET
WASHINGTON (Reuters) - Researchers on a safari for
microbes have found that human skin is populated by a
veritable menagerie of bacteria -- 182 species -- some
apparently living there permanently and others just
dropping by for a visit.
There's no need for alarm, said microbiologist Dr.
Martin Blaser of New York University School of
Medicine: the bacteria have been with us for quite a
while and some are helpful.
In research published on Monday in the Proceedings of
the National Academy of Sciences, Blaser and his
colleagues took swabs from the forearms of six healthy
people to study the bacterial populations in human
skin -- our largest organ.
"We identify about 182 species," Blaser said in an
interview. "And based on those numbers, we estimate
there are probably at least 250 species in the skin."
"In comparison," Blaser added, "a good zoo might have
100 species or 200 species. So we already know that
there are as many different species in our skin, just
on the forearm, as there are in a good zoo."
Bacteria are single-celled microorganisms believed to
have been the first living things on Earth. While some
cause disease, bacteria also reside normally in our
bodies, for example in the digestive tract, performing
"Without good bacteria, the body could not survive,"
added Dr. Zhan Gao, a scientist in Blaser's lab
involved in the study.
The researchers noted that microbes in the body
actually outnumber human cells 10-to-1.
"Our microbes are actually, in essence, a part of our
body," Blaser said.
"We think that many of the normal organisms are
protecting the skin. So that's why I don't think it's
a great idea to keep washing all the time because
we're basically washing off one of our defense
layers," Blaser added.
It has long been known that bacteria reside in the
skin, but Blaser and his colleagues used a
sophisticated molecular technique based on DNA to
conduct a rigorous census.
The inhabitants proved to be more diverse than had
been thought, with about 8 percent of the species
previously unknown, the researchers found.
Some bacteria seemed to be permanent residents of the
skin, with four genera -- Staphylococcus,
Streptococcus, Propionibacteria and Corynebacteria --
accounting for a bit more than half the population.
Others were more transient.
In each person, the population of bacteria changed
over time although a core set existed for each.
The volunteers included three men and three women, and
the findings suggested the two sexes may differ in the
bacteria they tote along.
The researchers previously had studied bacteria in the
stomach and esophagus. With this research, they found
that the insides of the body and the skin had major
differences in bacterial populations.
"Microbes have been living in animals probably for a
billion years. And the microbes that we have in our
body are not accidental. They have evolved with us,"
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