The genome of the toenail fungus and dozens of other types of fungi that live on the skin is deciphered

It turns out that in the toenails, there is a variety of 60 different types of fungi, but the record belongs to the heel - 80 different types

While humans have utilized the ability of yeast to produce bread and beer, the role of yeast and other types of fungi living on the human body is not fully known.

Researchers at the National Institutes of Health in the US have conducted a first-of-its-kind study of the genetic diversity of the fungi living on the skin of healthy adults in order to define the normal populations living on the skin and provide a framework for studying the conditions in which the fungi cause disease.

The surface of the human skin is a complex ecological environment for micro-organisms, including bacteria and viruses, known as the skin microbiome. Although fungal infections of the skin affect about 10% of the population (originally - 29 million Americans, AB) it is difficult to grow them in the laboratory, to diagnose them and of course to treat even the most common skin fungal symptoms such as nail fungus.

The team of researchers from the National Human Genome Institute (NHGRI) and the National Cancer Institute (NCI), both part of the National Institutes of Health (NIH), extended the genome sequencing research they conduct to bacteria and other organisms on the skin, using DNA sequencing techniques adapted to identify fungi. The results of the study appeared in the May 22 online issue of the journal Nature.

The researchers found that a certain type of Phytria, belonging to the species Malassezia is the ruler of the head and body. The hands, which host the widest variety of bacteria, are home to a relatively small number of fungi. In contrast, the feet, including the nails, heels and toes contain a huge variety of fungi.

The adaptation of DNA sequencing to the study of skin fungi is the natural opening in understanding the microbial life that coexists with us on our bodies" says NHGRI's scientific director, Dr. Daniel Kastner. "Together with the current sequencing of the genome that defines the diversity of bacteria, the analysis of the diversity of fungi will provide us with a better understanding of the microbial picture of the human body.

"Fungal communities occupy complex niches, even in the human body," says Dr. Heidi Kong, co-author and researcher in the dermatology branch of the NCI Cancer Research Center. "By gaining a more complete awareness of the ecosystems of the fungi and bacteria, we will be able to better identify skin diseases, including conditions that exist during cancer treatments."

The researchers collected samples from 14 areas of the body of ten healthy adults. Sequencing the DNA of the fungi in the samples resulted in the identification of DNA segments called phylogenetic markers, which can be counted and are used to distinguish one type of fungus from another. The sequencing effort generated over 5 million markers representing over 80 different species of fungi. In contrast, traditional culture preparation methods produced 130 colonies of fungi representing only 18 species.

They discovered that all sufferers of heel fungus host the same species of fungus on this site, however, nail fungus is caused by several different species of fungi.

"DNA sequencing reveals to us a large variety of fungi, even those that are difficult to grow in culture" says Dr. Julie Segara, senior research partner and senior researcher in the Department of Genetics and Molecular Biology at NHGRI. Specializing in the development of microbial DNA sequencing technology. "DNA sequencing allows us to learn infinitely more about the places where the fungi are the dominant organisms in the skin's microbiome."

The researchers identified fungi from two biological systems - Ascomycetes and Basidiomycetes, as part of the census of normal fungi in 14 sites in the skin. The most common type, Malassezia was present in 11 of the 14 samples on the skin. The researchers found Malassezia fungi on the skin of all the healthy volunteers, both on the back of the hand, behind the ears, in the nostril and on the heels of the feet. The heels were also home to other types of fungi, including the families genera Aspergillus, Cryptococcus, Rhodotorula, and Epicoccum.

"The DNA sequencing allowed us to identify and differentiate between different species of fungi and to come to the conclusion that the diversity of the fungi depends on the site of the body more than on the person from whom the samples were taken." says Dr. A. Kong, a dermatologist who explained why exactly these sites were chosen for testing. "Our research focused on areas of the skin where skin diseases related to fungi are common."
The most complex area, the heel, contains about 80 different types of fungi. The researchers discovered about 60 types in the toe nail pad and about 40 types in the toe membrane. Sites with a medium variety of fungi are found in the folds of the arm, inside the palm and the root of the arm and in each site 18-32 different types of fungi were found. Surprisingly, in the head and neck and body sites such as the back, back of the neck, inside the ears, behind the ears and between the eyebrows there are few types of fungi, between 2-10 types.

A comparison between the genome sequencing of the fungi and the genome sequencing of the bacteria living in the same areas on the skin shows the opposite picture, in the arms, where a large variety of bacteria was measured, there are few types of fungi. They discovered in the areas of the leg and in particular the foot the situation is exactly the opposite - a smaller variety of bacteria and a high variety of fungi. The researchers previously showed that it is possible to moisturize the variety of bacteria by measuring the moisture of the skin in the same area - is it dry, oily or wet. The variety of fungi seems to depend only on the specific location on the skin.

In addition, the researchers observed the similarity between the structure of the fungal community between identical sites on the right and left part of the subject's body. The fungal communities were also stable over time, with very little change when the same individuals were tested on two different occasions, three months apart.

"The data from the research provide us with a baseline about the normal state of humans that we didn't have until now," says Dr. Segera. "The bottom line is that our feet are inhabited by a variety of fungi, so you should be careful in changing rooms if you don't want to mix the fungi on your feet with someone else's."

to the notice of the researchers