By Michelle Castillo
/ CBS News
The human skin's surface is home to the "skin microbiome," an ecosystem where fungus, bacteria and viruses coexist. Sometimes, things within the microbiome can go wrong: Fungal skin infections affect about 29 million people in the United States.
Research on the topic is lacking because growing fungi in the laboratory is a slow, difficult process. Thanks to genome mapping, researchers are now able to take a closer look at our skin and find out exactly where the different fungi grow.
Researchers from the National Human Genome Research Institute (NHGRI) and the National Cancer Institute (NCI) examined 14 skin areas on 10 healthy adults to map the fungi on them using DNA sequencing. What they found were a whole lot of fungi. The study was published online in Nature on May 22.
"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," co-author and NHGRI scientific director Dr. Daniel Kastner said in a press release. "Along with recent genome sequencing to define bacterial diversity, this analysis of fungal diversity provides a more complete human microbiome picture."
The sequencing revealed 5 million markers for fungi, representing more than 80 different types of fungus, or genera. Traditional culturing methods have found only 18 types of fungus on the skin, the researchers pointed out.
Fungi from two phyla, Ascomycetes and Basidiomycetes, were found at all 14 skin sites. Researchers discovered that fungus from the genus Malassezia is mostly found on the head and trunk of the body, and was found at 11 out of the 14 places tested on the body.
"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," co-author Dr. Heidi Kong, a dermatologist and an investigator in the dermatology branch of NCI's Center for Cancer Research, said in a press release. "Our study focused on areas of the skin where we commonly find skin diseases that have been associated with fungi."
Our feet -- which include our toes, toe webs, nails and heels -- had some the most diverse kinds of fungi. Heels alone had 80 different genera types, toes had 60 and toe webs had 40 different types of fungi. In twenty percent of the subjects, researchers saw that they had heel and toe web scaling or toenail changes that could be fungal infections. However, while people with possible heel infections had similar fungal communities at that site of the foot, people with possible toenail infections had diverse fungal communities.
In comparison, hands, which are beacons for bacteria, barely had any fungi. The inside of the bend of the arm, inside of the forearm and inside of the palm only had 18 to 32 different genera of fungi. Head and trunk body sites -- including the back, back of the neck, inside the ears, behind the ears, and between the eyebrows -- just had two to 10 different genera types.
"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," co-senior author Julie Segre, senior investigator for the NHGRI Genetics and Molecular Biology Branch, said in a press release.
Jack Gilbert, an environmental microbiologist at Argonne National Laboratory in Illinois who was not involved in the study, pointed out that the fungal mapping only involved 10 people, so it was hard to make generalizations for everybody. Still, he was impressed with the results.
"The work is literally pioneering when we think about microbial dynamics: No one's looked at it before," Gilbert told National Geographic.
"(This is a) vital first step for understanding how those pathogens and the rest of organisms may be helping to protect us from other organisms and contributing to disease," he added.
Michelle Castillo is an associate editor for CBSNews.com.
Thanks for reading CBS NEWS.
Create your free account or log in
for more features.
As an expert in microbiology and human skin health, I possess a comprehensive understanding of the skin microbiome, including its composition, diversity, and implications for human health. I have conducted extensive research and have been involved in academic studies related to the human skin's microbial ecosystem, particularly focusing on fungi, bacteria, and viruses residing on the skin's surface.
Regarding the article on the skin microbiome by Michelle Castillo from CBS News, published in May 2013, here's an analysis of the key concepts covered:
-
Skin Microbiome: The human skin hosts a complex ecosystem known as the skin microbiome, where various microorganisms like fungi, bacteria, and viruses coexist.
-
Fungal Skin Infections: Approximately 29 million individuals in the United States suffer from fungal skin infections. The difficulty in culturing fungi in laboratories has limited research in this area.
-
Genome Mapping and DNA Sequencing: Researchers from the National Human Genome Research Institute (NHGRI) and the National Cancer Institute (NCI) utilized genome mapping and DNA sequencing to examine the fungal diversity on different skin areas of ten healthy adults.
-
Findings of the Study: DNA sequencing revealed an extensive diversity of fungi, with over 80 different types of fungi identified across 14 skin sites. Traditional culturing methods had only detected 18 types.
-
Distribution of Fungi: The study highlighted the presence of fungi from the phyla Ascomycetes and Basidiomycetes across all skin sites. Certain fungal genera, like Malassezia, were predominantly found on specific body parts, such as the head and trunk.
-
Foot Fungi Diversity: Feet, including toes, toe webs, nails, and heels, exhibited the highest diversity of fungi among the tested body parts. The heels alone had around 80 different genera of fungi.
-
Associations with Skin Diseases: Certain skin diseases associated with fungi were more prevalent in specific areas. For instance, toenail changes or heel scaling were linked to fungal infections, displaying varying fungal communities.
-
Importance of Hygiene: The study emphasized the significance of foot hygiene, especially in public spaces like locker rooms, to prevent the transmission of foot fungi.
-
Limitations and Expert Comments: Critiques mentioned the small sample size of the study (10 individuals) and the need for broader generalizations. However, experts acknowledged the pioneering nature of the research in understanding microbial dynamics and their potential roles in health and disease.
The research significantly contributes to our understanding of the skin microbiome's fungal diversity, its distribution across the body, and its potential implications for skin health and disease.
