Scientists find 20 unique microbes that decompose dead bodies

They’re going to have to change CSI and Silent Witness scripts: dead bodies appear to be quickly acted upon by a unique pack of about 20 microbes that begin the process of body decomposition, a US study has found.

The analysis could provide a better time signature to forensic scientists seeking to determine how long a person has been dead.

Irrespective of location, climate or time of year, this same group of bacterial and fungal organisms appears to latch onto a body and decompose it.

According to the scientists behind the research published today in Nature Microbiology this phylogenetically distinct network assembles as a body decomposes, particularly among mammals like humans, cattle, pigs and mice.

This network does not appear in “non-decomposition environments”.

“We see similar microbes arrive at similar times during decomposition, regardless of any number of outdoor variables you can think of,” says Jessica Metcalf, a microbiome scientist at Colorado State University.

Microbes have long been known as the foundation of all ecological food webs, essential to nutrient-cycling processes that break down dead plant and animal matter that in turn enrich soils that are harnessed by new plants and fungi for growth.

But while Metcalf sees the data having benefits for agricultural industries when it comes to how vertebrates decompose – “we’re opening a whole lot of avenues in basic ecology and nutrient cycling” – there might also be use in forensic investigations.

This study assessed 36 cadavers across 3 forensic anthropological facilities and specifically found the 20 specialist decomposers appeared on each of them over 3 weeks – likely transferred by insects – irrespective of the conditions in which the bodies were kept.

It’s suggested that this unique decomposer community can be used to calculate a time of death. Collaborators on the study have taken the ecological data to build a machine learning tool that can benefit forensic scientists in the field.

“When you’re talking about investigating death scenes, there are very few types of physical evidence you can guarantee will be present at every scene,” says David Carter, a forensic scientist at Chaminade University of Honolulu, who developed the system.

 “You never know if there will be fingerprints, or bloodstains or camera footage. But the microbes will always be there.”

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