Corpse Microbiome Reveals Telltale Forensic Secrets

Mammalian cadavers are a rare source of nutrients for forest ecosystems and one that microbes can break down three orders of magnitude faster than dead plant litter. Researchers led by Rob Knight at the University of California, San Diego, and Jessica L. Metcalf at the University of Colorado, Boulder, wondered how the community of cadaver microbes changes over time as they feast on a corpse’s concentrated source of proteins and lipids. That fare is much different than the megadose of polysaccharides found in plant matter. The team discovered that a cadaver’s microbiome changes in a sufficiently reproducible manner that forensic information can be inferred by examining which microbe diners are present (Science 2015, DOI: 10.1126/science.aad2646). In a study that included four decomposing human subjects and dozens of deceased mice, the team observed time-dependent, predictable increases in microbes involved in nitrogen cycling and amino acid degradation, including the breakdown of lysine and arginine into their foul-smelling by-products cadaverine and putrescine. The team proposes that a cadaver’s microbiome could be used to determine time of death, thereby complementing or improving upon the use of insects for cadaver dating.