Nitrogen cycling archaea make a new addition to the human skin microbiome

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Staphylococcus epidermidis,  a common skin bacteria, revealed after culturing a human handprint on an agar gel. Credit: National Geographic

Staphylococcus epidermidis, a common skin bacteria, revealed after culturing a human handprint on an agar gel.
Credit: National Geographic

Archaea are an evolutionary ancient lineage of microorganisms once believed to be restricted only to extreme environments such as deep sea vents and hot springs. Recently, scientists have discovered these organisms are present in a much broader range of moderate environments including the ocean interior. Now researchers at the University of Regensburg have discovered Archaea inhabit an environment even closer to home: your skin.

Skin, the largest human organ, has recently become the subject of intensive scrutiny by the Human Microbiome Project: a large multidisciplinary effort founded to characterize the entire assemblage of microorganisms present on the human body. Most  of the attention has been paid to bacteria present on human skin, and far less to their Archaeal counterparts.

However, several recent studies have revealed Archaea are present in so-called “clean rooms” used in hospitals, research facilities, and for spacecraft assembly. Given the most likely origin of Archaeal contamination in clean rooms is human occupants, scientists are now asking whether the bias towards a bacterially-dominated skin microbiome holds up under genetic scrutiny.

Scanning electron micrograph image of the human epidermis- a diverse microbial habitat. Credit: National Geographic

Scanning electron micrograph image of the human epidermis- a diverse microbial habitat.
Credit: National Geographic

The research team, led by Dr. Christine Moissl-Eichinger, obtained skin samples from 7 female and 6 male subjects. Each subject was asked to swab his/her entire torso to obtain a representative sample of a  “stable” skin environment. (While microbially-rich palm samples are more commonly used, in this case the researchers wanted an environment that did not come in frequent contact with the outside world in order to more accurately characterize the native skin fauna).They simultaneously took samples from a hospital clean room complex and two intensive care units. The scientists then extracted DNA and used genetic techniques (quantitative PCR and fluorescence in situ hybridization) to determine the abundance of Archaeal genetic markers.

They found that Archaea comprise up to 4% of the skin microbiome. While 4% may sound relatively minor, almost all the Archaea found on human skin belong to the group Thaumarchaota: the very same group found in clean rooms in both this and earlier studies. Thaumarchaota, also commonly found in soils, is thought to play a key role in the soil nitrogen cycle due to their ability to use ammonia, a common plant-available form of nitrogen, as their sole energy source. According to Moissl-Eichinger, Archaea present on our skin may act as a natural pH regulator, using up the ammonia that is emitted slowly but continuously.

While many questions remain about the origin and ecology of human skin Archaea, their unique metabolism and remarkable tenacity in clean rooms suggest this small component our our skin flora may play an unexpectedly large role.

Credit: skinmicrobiome.wordpress.com

Credit: skinmicrobiome.wordpress.com

The original article can be found here.

 For more information on the skin microbiome

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