Hair is one of the most common trace evidence gathered at crime scenes, note researchers led by Murdoch University's Michael Bunce in their Investigative Genetics paper. But if the hairs don't include the roots, they usually don't contain enough DNA for STR analysis.
Instead, Bunce and his colleagues examined whether the microbes living on hairs could be identified through metagenomic approaches and used to generate a unique microbial profile for the individual from whom they came.
They surveyed the bacterial communities of scalp and pubic hairs obtained from seven adults, including one co-habitating couple, at three different points in time. As the researchers report in their paper, they found that scalp hairs harbor about 50 to 55 different types of microbes while pubic hairs have some 73 to 76 types of microbes. Additionally, they noted that communities were personalized and consistent over time.
There was one instance in which the researchers noted that two individuals had more similar pubic hair microbial profiles at one time point as compared to the earlier collection times — these samples had been collected from the romantic couple a day after they'd had sex.
"This surprising result indicated that humans swap external microbes during intercourse, suggesting that the microbiome could be useful in forensic analysis on sexual assault cases," Discover's D-brief blog adds.