Forensic science: microbiota to the rescue?

According to a study, variation in the oral microbiota could be used as evidence for investigators in medical/legal affairs.

With more than 1000 bacterial species, the oral microbiota is the second most populated after the gut. Like the intestinal microbiota, the oral microbiota plays a huge role in how the body decomposes after death, and analyzing it could be a real aid to forensic scientists.

Researchers studied the postmortem microbiome (or thanatomicrobiome, the genome of bacteria after death) in order to identify the bacterial species involved in the decomposition of the human body, and to describe the successive changes in the microbiota, from the start of putrefaction until complete skeletonization, in precise detail.

They worked on three cadavers, from which they took oral samples every day throughout the entire decomposition process. There are five steps: fresh, bloat, active decay, advanced decay, and dry/remains. Each cadaver went through the process at its own pace: decomposition of the skull on days 6, 7, and 9; complete skeletonization on days 7, 9, and 11 respectively.

DNA analysis and sequencing from the oral microbiota allowed them to identify the bacteria that take over at each of the five stages of body decomposition. The authors observed that changes in the bacterial ecosystem depend on the availability of oxygen, which changes over time. They firmly believe that analysis of the oral microbiota will be able to be used to determine the time of death relatively accurately. Elementary, my dear Watson!*

Sources :
Adseria Garriga J., Quijada NM., Hernandez M., Lázaro DR., Steadman D., Garcia-Gil J. Dynamics of the Oral Microbiota as a Tool to Estimate Time Since Death. Mol. Oral. Microbiol. 2017 Jun 27. doi: 10.1111/omi.12191.