Authentication of human identity plays a prominent role in our society, particularly within the field of forensic science. There are a number of different biological indicators that can be used to confirm one’s identity, such as DNA or fingerprints. However, more often than not, forensic investigators require more than one form of biological evidence to establish a higher probability of identity confirmation (Black & Thompson 2006). Various scientific advances are providing innovative ways of extracting forensically pertinent information from biological samples (Kayser & de Knijff 2011). Of recent discovery has been the concept of humans emitting their “personal microbial clouds” through breathing (Meadow et al. 2015).
The human body harbours up to 100 trillion microbial species, most of which we have developed a symbiotic relationship with (Ursell et al. 2012). This community of microbes is collectively known as the human microbiota, and inhabit multiple areas in and on our bodies, such as our skin, gut, and respiratory tract (Nelson et al. 2010). Studies have shown that these microbial species are not only unique to their habitat within the body, but are also unique to each individual (HMP Consortium 2012). This discovery has led scientists to investigate whether humans emit a detectible “microbial cloud” into their surrounding that is sufficiently distinguishable between individuals (Meadow et al. 2015).
It is not a great surprise that humans leave behind traces of bacteria after having direct contact with surfaces or sneezing into the air. However, a team of researchers led by Dr. James Meadow from the University of Oregon carried out an experiment to test whether or not this bacterial emission varies among individuals and can serve as a form of identification. For this experiment, 11 healthy participants were placed in a sanitized custom climate chamber, once alone in the chamber and once with other participants in the same chamber. The air going in and out of the chambers was filtered to collect airborne emissions from the participants. In addition, various petri dishes were placed around the participants to collect settled particles. The results from two different sampling periods, 2 and 4 hour duration, were analyzed using high-throughput DNA sequencing of the microbes found in airborne and settled particles. The results showed that bacterial emission collected in the air filters mirrored those found in the petri dishes. Furthermore, each participant’s microbial cloud was compared among all participants, and the results proved that the samples from each person is statistically distinct and identifiable to that person. However, results of each participant were more discernible after the 4 hour sampling periods, as it gave enough time for the participants to emit enough bacterial particles into the air. Lastly, the bacterial emissions obtained from the 11 participants were consistent for each individual.
This new method of human identification can lead to various applications within the field of forensic science, such as using indoor bioaerosols to detect who had been in the room (Meadow et al. 2015). However, further research needs to be carried out in order to determine whether personal microbial clouds are still detectable within large indoor spaces, among crowded areas and in the presence of background dust particles (Meadow et al. 2015). Nevertheless, this discovery can lead to many doors opening for the future of criminal investigations and public safety.
References:
Black, S. & Thompson, T. eds., 2006. Forensic Human Identification: An Introduction, CRC Press. Available at: https://books.google.com/books?id=2o6iyCnwmDEC&pgis=1 [Accessed September 26, 2015].
HMP Consortium, 2012. Structure, function and diversity of the healthy human microbiome. Nature, 486(7402), pp.207–14. Available at: http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=3564958&tool=pmcentrez&rendertype=abstract [Accessed July 11, 2014].
Kayser, M. & de Knijff, P., 2011. Improving human forensics through advances in genetics, genomics and molecular biology. Nature reviews. Genetics, 12(3), pp.179–92. Available at: http://www.ncbi.nlm.nih.gov/pubmed/21331090 [Accessed September 26, 2015].
Meadow, J.F. et al., 2015. Humans differ in their personal microbial cloud. PeerJ, 3, p.e1258. Available at: https://peerj.com/articles/1258 [Accessed September 22, 2015].
Nelson, K.E. et al., 2010. A catalog of reference genomes from the human microbiome. Science (New York, N.Y.), 328(5981), pp.994–9. Available at: http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2940224&tool=pmcentrez&rendertype=abstract [Accessed September 25, 2015].
Ursell, L.K. et al., 2012. The interpersonal and intrapersonal diversity of human-associated microbiota in key body sites. The Journal of allergy and clinical immunology, 129(5), pp.1204–8. Available at: http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=3342686&tool=pmcentrez&rendertype=abstract [Accessed September 25, 2015].