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Complex communities of microbes live on the surface
of our bodies. These fungi, bacteria and viruses are
collectively known as the skin microbiome.
A team from NIH’s National Human Genome Research
Institute (NHGRI) and National Cancer Institute (NCI)
previously used genomic techniques to study skin
bacteria and found diverse bacterial communities
that varied between people and by skin site.
In their new study, the team used a similar genomic
approach to gain a better understanding of the fungi
that live on our skin.
Fungi include molds, mushrooms, and the yeast that
are used to ferment bread and beer. Fungi have been
associated with many skin diseases and conditions,
including athlete’s foot, eczema, dandruff and
toenail infections.
Malassezia fungi.
Credit: Janice Haney Carr, CDC.
Fungal skin infections affect an estimated 29
million people nationwide. But fungi can be slow and
difficult to grow in laboratories, making fungal
infections hard to identify and treat.
As
described online in Nature on May 22, 2013, the
scientists collected samples at 14 body sites from
10 healthy adults. They focused on a fragment of DNA
shared by all fungi (the intervening internal
transcribed spacer 1, ITS1, of ribosomal RNA) that
could be used to classify fungi at the genus level
with greater than 97% accuracy.
By
generating more than 5 million ITS1 sequences from
the samples, the team was able to identify more than
80 genus-level fungal types living on human skin. In
contrast, traditional culturing methods could
identify only 18 types.
Ascomycetes and Basidiomycetes were found at all the
skin sites. Fungi of the genus Malassezia were the
predominant type on 11 of the 14 sites, including
behind the ears, in nostrils, on the back, and on
the arms.
The
team found that heels, which don’t show extensive
bacterial diversity, were the most complex site for
fungi, with about 80 types represented. Toe webs,
with about 60 types, and toenails, with 40, had the
next highest levels of fungal diversity. Hands and
arms, which harbor a great diversity of bacteria,
had relatively few types of fungi.
Fungal communities on the core body were quite
stable over time, with little change when tested up
to 3 months apart. In contrast, fungi on the feet
altered considerably over 3 months, perhaps
reflecting more environmental exposure.
“The
fungal communities on the human body are complex and
site-specific,” says co-senior author Dr. Heidi Kong
of NCI. “By gaining a more complete awareness of the
fungal and bacterial ecosystems, we can better
address associated skin diseases, including fungal
infections, which can be related to cancer
treatments.”
“The
data from our study gives us a baseline about normal
individuals that we never had before,” says
co-senior author Dr. Julie Segre of NHGRI..
For more information
National Institutes of Health (NIH)
(MDN)
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