Human Thanatomicrobiome Succession and Time Since Death

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.

An Experiment to Characterize the Decomposer Community Associated with Carcasses (Sus scrofa domesticus) on Oahu, Hawaii

“…Postmortem microbial communities, regardless of carcass species, are regularly dominated by bacteria from phyla Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria (26)(27)(28)(29)(30)41) with other phyla such as Verrucomicrobia and Fusobacteria observed with some regularity (39,41,42). The current results complement these studies by demonstrating that bacteria from these same phyla can be cultured under aerobic and anaerobic conditions.…”

“…As observed by Chun et al (25), this habitat selected for a microbial community comprising phyla Firmicutes and Proteobacteria. These phyla are regularly associated with decomposing remains (26)(27)(28)(29)(30) and are likely reducing sulfur compounds to acquire energy (Fig. 6c).…”

“…These microbes contribute significantly to decomposition (e.g., putrefaction) and can release volatile organic compounds that attract insects and scavengers . Recent postmortem microbiology has demonstrated that bacterial phyla Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria are regularly associated with decomposing remains regardless of carcass species, season, or soil type . However, despite the surge of interest in postmortem microbiology, few studies have investigated the microbial communities associated with insect larval masses.…”

Necrobiome framework for bridging decomposition ecology of autotrophically and heterotrophically derived organic matter

“…Nutrients and particles also are dispersed by mobile micro-(e.g., fungi, protists) or macro-saprotrophs (e.g., flies) that act as vectors of the organic matter, microbes, and elements. The dispersal of these materials can occur in multiple Hyde et al (2015), Javan et al (2016) ways: (1) trophic transfer where the microorganisms and elements are ingested but not assimilated, and then egested after saprotroph movement away from the necromass source;…”

Manner of death and demographic effects on microbial community composition in organs of the human cadaver

“…A previous microbial survey of internal organ tissues (e.g., brain, heart, liver, and spleen) of four cadavers, associated with a homicide, suicide, over-dose, and accidental death cases, demonstrated that the obligate anaerobe, Clostridium was found in cadavers of varying PMIs, while the facultative anaerobe, Lactobacillus , was more abundant in cadavers with shorter PMIs (12). Other investigations performed exploratory analyses of bacteria present in mouth and rectal scrapings taken at the onset and end of the bloat stage of corpses decomposing in a natural setting (32).…”