Genomic Survey Of Fungal Diversity On Human Skin
May 23, 2013

The Fungus Among Us: Your Skin Is Crawling With Fungi, Especially Your Feet

Brett Smith for - Your Universe Online

Your skin is literally covered with almost 200 different kinds of fungi.

This isn´t the scene out of some twisted horror movie — it´s the conclusion of a team of American researchers who recently created a topographic map of fungi typically found on living human skin.

To create their map, scientists from the National Human Genome Research Institute (NHGRI) and the National Cancer Institute (NCI) used genetic sequencing technology to identify the different species of fungus, according to their report in the journal Nature.

"Applying DNA sequencing to a study of the skin's fungi is the natural progression in understanding microbial life that co-exists on our bodies," said co-author Dr. Daniel Kastner, a scientific director at the NHGRI. "Along with recent genome sequencing to define bacterial diversity, this analysis of fungal diversity provides a more complete human microbiome picture."

"Fungal communities occupy complex niches, even on the human body," added Dr. Heidi Kong, M.D., co-senior author and a dermatologist NCI's Center for Cancer Research. "By gaining a more complete awareness of the fungal and bacterial ecosystems, we can better address associated skin diseases, including skin conditions which can be related to cancer treatments."

The researchers took samples at 14 body sites from 10 healthy adults. The team sampled the ear canal, back of the head, heels, arms, toenails, and between the toes, among other places.

Using fragments of DNA called phylogenetic markers, the team was able distinguish one type of fungus from another. While traditional culturing methods produced 130 colonies of fungi representing 18 fungal types, the genetic analysis generated over 5 million markers representing more than 80 fungal types.

"DNA sequencing reveals the great diversity of fungi, even those that are hard to grow in culture," said co-author Julie Segre, a researcher with the NHGRI Genetics and Molecular Biology Branch. "DNA sequencing enabled us to learn immeasurably more about where fungi predominate as a part of the human skin microbiome."

According to the study, the most diverse fungal habitat is the heel of the foot, with about 80 types of fungi. Other hotspots included toenail clippings, with about 60 types, and between the toes, with 40. Moderate levels of fungi included include the palm, forearm and inside the elbow, with about 18 to 32 types.

"DNA sequence-based methods of identification enabled us to differentiate among species of fungi and to conclude that the diversity of fungi is highly dependent on the body site rather than the person who is sampled," Kong said. “Our study focused on areas of the skin where we commonly find skin diseases that have been associated with fungi."

When comparing fungal diversity data with skin bacteria on the same adults, the team discovered that arms have high measures of bacterial diversity, yet lower fungal diversity. They found the opposite to be true for foot locations.

"The data from our study gives us a baseline about normal individuals that we never had before," Segre said. "The bottom line is your feet are teeming with fungal diversity, so wear your flip flops in locker rooms if you don't want to mix your foot fungi with someone else's fungi."