Hair microbiota: a new geolocation tool?
The microbiota of body hair does not have the same composition as that of head hair, which is more influenced by the environment, according to an American study. This discovery opens up new prospects, especially in the forensic field.
Like the skin, hair hosts its own microbiota which is subject to intra- and inter-personal variations that make it unique, turning it into a valuable source of information for forensic investigations. To assess the impact of environmental factors (diet, climate, age, place of origin, etc.), American researchers compared the hair microbiota sampled from the scalp and pubic region of adults living in different parts of the United States.
Whatever the length of pubic hair, its microbiota was found to be more abundant but less diverse than that of head hair, whose length was found to influence bacterial abundance beyond 4 cm. Four bacterial species dominate this ecosystem, but only two are common to both types of hair: Staphylococcus and Corynebacterium. The former are present at similar levels, while the latter are significantly more abundant in pubic hair since they favor moist environments. Finally, Propionibacterium, which is predominant in the skin and hair follicle (where hair roots grow) floras, is absent from the microbiota of hair roots, probably because the environment does not contain enough sebum and too much oxygen. These findings confirm that environmental conditions have an impact on the nature of bacterial species making up the microbiota.
New avenues in forensic research?
This study thus confirms that, similarly to skin microbiota, hair microbiota varies depending on the location on the body. Its composition is different than that of hair follicles but is close to that of the skin covered by hair. However, the hair flora retains different geographical signatures likely influenced by lifestyle and location. According to the authors, the greater impact of environmental factors on head hair microbiota than on pubic hair microbiota opens up new avenues for forensic science, especially to determine where a person comes from.
Lauren Brinkac et al. Spatial and Environmental Variation of the Human Hair Microbiota. Scientific Reports (2018) 8:9017, DOI: 10.1038/s41598-018-27100-1