This article discusses the potential and the challenges in adopting the human microbiome as a tool in forensics.
The NIH-funded ‘Human Microbiome Project’ (HMP) has significantly improved the scientific and public recognition of the vital importance of symbiont ecology to host health and development (Consortium, 2012; Methé et al., 2012; Grice, 2015). There are approximately as many bacterial cells in our body as human cells (Sender et al., 2016) and the compliment of bacterial taxa, especially at the subspecies level, appears to be unique to each person (Zhu et al., 2015) offering a compelling opportunity to develop a new identifiable marker unique to the individual. The microbiome is even unique in identical twins (Goodrich et al., 2014), theoretically offering an opportunity to increase identity resolution over that possible with human genome evidence; however, the microbiome changes over time in an individual (Oh et al., 2016), so how can it be used to identify a person? Although the relative proportions of the bacteria do change, the composition of the community appears to be relatively stable (Caporaso et al., 2011; David et al., 2014), although this stability and continued identifiability are areas of active research. Interestingly, the fluctuations in the structure and composition of the microbiome may contain useful information that could also be used for forensic purposes. Human microbial fingerprinting should never replace traditional DNA profiling techniques; however, in the future, it could help augment existing trace evidence options for forensic researchers. This will require substantial investment in standardization and implementation of microbiome profiling techniques, as well as the development of detection technologies that could automate or rapidly advance microbiome profiling. (publisher abstract modified)