Microorganisms responsible for the decomposition of human corpses may provide clues to forensic scientists when investigating fatalities. This was demonstrated by a recent study in which scientists observed the bodies of deceased people for several weeks in accordance with the needs of science.

During decomposition, in which fungi and bacteria often play a role, dead biomaterial is processed and converted into nutrients for new biological processes in soil and plants. Although many studies have been devoted to decomposition, authors of past studies have paid more attention to the decomposition of dead plant biomass. Unlike plants, animal carcasses, including humans, are rich in easily decomposed proteins and fats. However, how their decay affects biogeochemical processes and the ecology of communities has been less studied.

A team of scientists from Colorado State University (Fort Collins, USA) undertook to fill this gap. Together with colleagues from other American universities, they tracked the decomposition of 36 human bodies transplanted for scientific research.

Observations were conducted during winter, spring, summer and fall at three research centers in the states of Colorado, Texas and Tennessee. Each of these places with a temperate or semi-arid climate contained 12 bodies (three for each season).

People’s bodies were placed on the ground in the open air, which is not normally done. Nothing could protect the bodies from the effects of weather and invertebrate scavengers. For 21 days, scientists took samples of the skin of the dead and the soil near the bodies and then isolated DNA from them. The results were published in the journal Nature Microbiology.

The study found that regardless of location, climate or season, decomposing human bodies produce a universal microbial community with increased metabolic efficiency to process fat- and protein-rich compounds. Key destructors are rarely found in nondissociative environments. According to scientists, these are specific to terrestrial flesh rot.

Using genomic and metagenomic analyses, as well as metabolomic profiling data, the authors reconstructed the processes occurring in the soil adjacent to the corpses and showed how fungi and bacteria jointly metabolize decomposition products. Researchers believe that important carriers of these microorganisms are insects such as flesh flies, carrion beetles, and others.

Additionally, scientists have shown that it is possible to create a model for determining age at death using data on the microbial chronology of corpse decomposition and machine learning techniques. The most effective model allowed researchers to accurately estimate the time since death to an accuracy of plus or minus three days. The authors believe such a tool could be useful in forensics.