Abstract
The thanatomicrobiome (thanatos, Greek for death) is a relatively new term and is the study of the microbes colonizing the internal organs and orifices after death. Recent scientific breakthroughs in an initial study of the thanatomicrobiome have revealed that a majority of the microbes within the human body are the obligate anaerobes, Clostridium spp., in the internal postmortem microbial communities. We hypothesized that time-dependent changes in the thanatomicrobiome within internal organs can estimate the time of death as a human body decays. Here we report a cross-sectional study of the sampling of 27 human corpses from criminal cases with postmortem intervals between 3.5–240 hours. The impetus for examining microbial communities in different internal organs is to address the paucity of empirical data on thanatomicrobiomic succession caused by the limited access to these organs prior to death and a dearth of knowledge regarding the movement of microbes within remains. Our sequencing results of 16S rRNA gene amplicons of 27 postmortem samples from cadavers demonstrated statistically significant time-, organ-, and sex-dependent changes. These results suggest that comprehensive knowledge of the number and abundance of each organ’s signature microorganisms could be useful to forensic microbiologists as a new source of data for estimating postmortem interval.
Highlights
Human Microbiome Project (HMP) metagenomic sequencing studies characterized the complexity of the human microbiome at numerous body sites, highlighting significant differences between microbial communities within and among individuals[1]
As a human body decays, microbes proliferate in the blood, liver, spleen, heart and brain in a time-dependent manner; the relative abundances of microbes will vary by respective body organ and postmortem interval (PMI)[5]
To investigate thanatomicrobiomic profiles generated by 16S rRNA gene amplicon sequencing, we selected and analyzed the internal organs, buccal cavities, and/or blood of 27 human corpses from actual criminal cases with postmortem intervals between 3.5–240 hrs were collected (Table S1)
Summary
Human Microbiome Project (HMP) metagenomic sequencing studies characterized the complexity of the human microbiome at numerous body sites, highlighting significant differences between microbial communities within and among individuals[1]. The thanatomicrobiome is the postmortem microbial community of the human body, which involves a successional process where trillions of microbes inhabit, proliferate, and die internally and externally throughout the dead body, resulting in temporal shifts in community composition over time[4,5]. It is presumed that the thanatomicrobiome of certain organs is not immediately affected by gut-associated microorganisms that proliferate rapidly after human death[13]. It was once a long held belief that human internal organs were sterile in living hosts[14,15]. We produced a microbial catalogue of the thanatomicrobiome, which may establish a useful forensic tool and provide constructive information to those who study human remains
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