Scientists discover 662 new microbes — in 95 belly buttons

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Scientists discover 662 new microbes — in 95 belly buttons
Laura Shin | July 4, 2011 08:50pm PDT
A study of the bacteria in 95 belly buttons — including those of
science bloggers — illustrated our microbial ignorance.

The Belly Button Biodiversity Project sounds like a cartoon version of
a science experiment, but a venture by that name is turning up serious

In February, biologists and science communicators from North Carolina
State University and the North Carolina Museum of Natural Sciences
began collecting swabs of bacteria from people’s belly buttons to find
out what microorganisms their bodies were hosting.

The results

After getting belly button swabs at science events in North Carolina
and from science bloggers, the researchers have finished their first

In just 95 cultures, they’ve found 1,400 bacterial strains, 662 of
which cannot even be grouped to the biological classification of
family, “which strongly suggests that they are new to science,” team
leader Jiri Hulcr of North Carolina State University told New
Scientist. (The order of biological classification goes kingdom,
phylum/division, class, order, family, genus, species.)

While it appears belly button bacteria can be diverse, a core group of
about 40 species accounts for about 80% of all the bacteria in our
belly buttons. This is astounding considering that the world’s
microbes outnumber all the species in the animal kingdom.

The New York Times science writer and Discover blogger Carl Zimmer
found that his belly button is home to 53 species, which he was told
is a “whopping” number.

Only a small fraction of my belly button bacteria were common among
the other 89 volunteers. The microbes I share with most other
volunteers tend to be ordinary skin dwellers that are typically
harmless … But out of 53 species, 35 were present in only 10 or fewer
other volunteers. And 17 species in my navel didn’t show up in anyone
else. In the column for notes in [the researcher's] spreadsheet, he’s
annotated these species with scientific descriptions like “weird one”
and “totally crazy.”

It seems Zimmer was not the only subject with strange belly button
bacteria: Incredibly, a few sequences of DNA were so unusual that the
only conclusion the scientists could make about them were that they
are bacteria.

The analysis

The researchers limited themselves to analyzing DNA from bacteria,
choosing to exclude fungi, viruses and other microorganisms.

But just identifying the bacteria alone is a challenge. The scientists
had the swabs’ “DNA barcodes” read (meaning that sequences of the gene
for 16S ribosomal RNA were read) to help study the evolutionary
relationships between the bacteria. They then compared these sequences
to millions of DNA sequences in public databases.

However, the smallest unit by which scientists could match these
barcodes was 16S ribosomal RNA gene sequences that differed by 3% or
less — which, in mammals, would be like lumping dogs and cats together

For belly button bacteria research, it means that two strains that
“match” taxonomically — such as a belly button strain and a species
recognized as inhabiting the deep ocean — could actually be separated
by several million years of evolution.

New frontier in microbiology

The astonishing number of new microbes discovered in the very
beginning stages of this belly button experiment reflects how ignorant
we are of microbial diversity.

According to New Scientist:

the inhabitants of our navels seem weird because biologists haven’t
sampled sufficiently extensively to document the full diversity of
microbial life in a variety of habitats. [Hulcr] likens reactions to
the first round of belly button results to the astonishment of the
first European explorers seeing African big game — which today seem
commonplace. ‘Now you’re expecting rhino and elephants,’ Hulcr says.

While the bacterial cultures will never be quite as exciting as rhino
or elephants, it is interesting to see how different the cultures

See photos of some swabs below, and browse the belly button bacterial
photo galleries on the Belly Button Diversity Project site.