By Kylie Finnegan
Fungi, bacteria, protozoa - they’re all microscopic creatures that inhabit every last corner of the Earth, able to survive in extreme environments and unusual circumstances. The human body provides some of these unique environments and acts as a host for microbes of countless varieties. The communities of prokaryotic organisms living on and inside the human body are referred to collectively as the microbiome, and researchers have found that individual microbiomes can have high specificity from person to person (Grice et al., 2009). What makes the microbiome unusual is that it is an entirely non-human entity, yet it is so impactful to the human body because of the sheer number of microbes living within us. Every person’s microbiome is like a signature - an individualized identifier. The implications of this microbiome personalization include everything from forensics to medicine, but one major question remains: can samples of microbiome populations be transferred from one person to another?
A 2019 study conducted by Neckovic et al. aimed to answer this question through an examination of the behavior of the hand skin microbiome. They found that there was a significant direct transfer of microbes from one person to another through a vigorous handshake. The notable differences in the composition of each person’s hand skin microbiome after the handshake indicated a mutual swapping of microorganisms through touch. By sequencing DNA collected from a swab of a person’s hand, it is possible to construct a microbial profile, or a highly unique community of microbes, belonging to that individual (Neckovic, van Oorschot, Szkuta, & Durdle, 2019). The different microbial species and changes in species concentrations post-handshake were like a new stamp on the original microbial profile that highlighted migrant microbes. The comparison between the original DNA and the post-handshake DNA that were collected allowed Neckovic et al. to determine how much genetic information is transferred between two people through touch. As it turned out, it is quite a lot.
The study determined that skin microbiome components had been transferred between participants through direct contact (a handshake) as well as through indirect contact (touching the same surfaces) (Neckovic, van Oorschot, Szkuta, & Durdle, 2019). This transfer actually influenced each individual’s microbial signature, making it more diverse after interaction with another person’s microbial signature. In fact, the researchers were able to tell which participants had shaken hands with each other based on the microbes left behind by the brief direct contact of the handshake, or the brief contact of both participants with the same surface.
The ability to identify individual people by their personalized microbial stamp has certain implications, particularly in the field of forensic science. Now that the usage of DNA analysis techniques are common in investigative police work, the utility of microbiome DNA analysis could provide something of a back-up plan. Often, there is no human DNA left to collect at crime scenes, but the easy transferability and high specificity of microbiome DNA means that more genetic material could be available, with an almost equal level of identifying ability. The study of human microbiome compositions and transfer could allow for breakthroughs in genetic analysis of forensic evidence, change the way people look at the non-human genes they constantly host.
Neckovic, A., van Oorschot, R.A.H., Szkuta, B., Durdle, A. (2019). Investigation of direct and indirect transfer of microbiomes between individuals. Forensic Science International: Genetics, 45, 102212. doi.org/10.1016/j.fsigen.2019.102212
Grice, E.A., Kong, H.H., Conlan, S., Deming, C.B., Davis, J., Young, A.C., … Segre, J.A. (2009). Topographical and Temporal Diversity of the Human Skin Microbiome. Science, 324, (5931), 1190-1192. doi: 10.1126/science.1171700