Gee,
they are still working out what sorts of things are living on our skin. Not just bacteria, but archaea:
The researchers conducted both genetic and chemical analyses of
samples collected from human volunteers ranging in age from 1 to 75.
They found that archaea (pronounced ar-KEY-uh) were most abundant in
subjects younger than 12 and older than 60. Their study has been
published in Scientific Reports (a Nature journal) in an article titled, "Human age and skin physiology shape diversity and abundance of Archaea on skin."
"The skin microbiome is usually dominated by bacteria," said Hoi-Ying
Holman, director of the Berkeley Synchrotron Infrared Structural
Biology (BSISB) Program and a senior author on the paper. "Most of the
scientific attention has been on bacteria, because it's easier to
detect. Based on the literature, six years ago we didn't even know that
archaea existed on human skin. Now we've found they're part of the core
microbiome and are an important player on human skin."
These are usually tough bugs:
It was not until the 1970s that scientists realized how different
archaea were from bacteria, and they became a separate branch on the
tree of life -- the three branches being Bacteria, Archaea, and Eukarya
(which includes all plants and animals). Archaea are commonly found in
extreme environments, such as hot springs and Antarctic ice. Nowadays it
is known that archaea exist in sediments and in Earth's subsurface as
well, but they have only recently been found in the human gut and linked
with the human microbiome....
This study stemmed from a planetary protection project for NASA and
the European Space Agency. "We were checking spacecraft and their clean
rooms for the presence of archaea, as they are suspected to be possible
critical contaminants during space exploration -- certain
methane-producing archaea, the so-called methanogens, could possibly
survive on Mars," Moissl-Eichinger said. "We did not find many
signatures from methanogens, but we found loads of Thaumarchaeota, a
very different type of archaea that survives with oxygen."
At first it was thought the Thaumarchaeota were from the outside, but
after finding them in hospitals and other clean rooms, the researchers
suspected they were from human skin. So they conducted a pilot study of
13 volunteers and found they all had these archaea on their skin.
As a follow-up, which is the current study, they tested 51 volunteers
and decided to get a large range in ages to test the age-dependency of
the archaeal signatures. Samples were taken from the chest area. The
variations in archaeal abundance among the age groups were statistically
significant and unexpected. "It was surprising," Holman said. "There's a
five- to eightfold difference between middle-aged people and the
elderly -- that's a lot."
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