Human skin is a virtual zoo, according to U.S. researchers who found nearly 200 species of bacteria, including about 15 unknown to science, on the forearms of test subjects.
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SYDNEY: Human skin harbours startling variety of bacteria, including 15 species new to science, according to U.S. researchers.
"The skin is home to a virtual zoo of bacteria," said Martin J. Blaser of the New York University Medical Centre, whose team published their findings this week in the U.S. journal Proceedings of the National Academy of Sciences. His team analysed samples of skin from human forearms and found evidence of 182 different species of bacteria, eight per cent of which were unknown species that had never before been described.
The researchers analysed the microbe community on the forearms of six healthy subjects, three men and three women. "This is essentially the first molecular study of the skin," said Blaser. The skin has been, he explained, terra incognita; an unknown world that he and his colleagues set out to explore.
"Many of the bacteria of the human body are still unknown," said Blaser. "There are probably fewer than ten labs in the U.S. looking at this question … it is very intensive work," he explained of the three year-long research project.
Sampling from the 6 test subjects was conducted in a clean room so the samples didn't risk contamination. "We didn't tell them (the test subjects) to be particularly clean, we just made sure they didn't take antibiotics up to one month prior to the test," explained lead author Zhan Gao, also of NYU. Antibiotics, which kill bacteria, might have altered the microbial community on the skin.
According to the study, while bacterial populations for individuals varied over time there existed a core set of bacteria for each test subject. "What that suggests," added Blaser, "is that there is a scaffold of bacteria present in everybody's skin. Some stay and others come and go."
Blaser's laboratory has previously examined the bacterial community living in the stomach and the oesophagus. "Ultimately what we want to do is compare disease and health," said Blaser. Keeping bacterial populations in our body stable may be part of staying healthy".
The researchers found that only four species, including Propionibacterium acnes, a species linked to acne, and Streptococcus mitis, which can cause an inflammation of the heart called endocarditis, were common to all the test subjects. "This is a surprise," said Gao. "But many things affecting the skin affect bacteria, such as the weather, exposure to light, and cosmetics use."
The study found that almost three-quarters of the total number of bacteria species were unique to individual subjects. Additionally, many were unique to males and females, suggesting that the skin surface is highly diversified in terms of the bacteria it harbours.
According to Blaser, while the composition of a skin bacterial community can vary over time, the skin is never devoid of bacteria. However, he noted, in healthy individuals these bacteria do their human hosts no harm.
