Function of bacterial community dynamics in the formation of cadaveric semiochemicals during in situ carcass decomposition

Abstract

The decomposition of dead mammalian tissue involves a complex temporal succession of epinecrotic bacteria. Microbial activity may release different cadaveric volatile organic compounds which in turn attract other key players of carcass decomposition such as scavenger insects. To elucidate the dynamics and potential functions of epinecrotic bacteria on carcasses, we monitored bacterial communities developing on still-born piglets incubated in different forest ecosystems by combining high-throughput Illumina 16S rRNA sequencing with gas chromatography-mass spectrometry of volatiles. Our results show that the community structure of epinecrotic bacteria and the types of cadaveric volatile compounds released over the time course of decomposition are driven by deterministic rather than stochastic processes. Individual cadaveric volatile organic compounds were correlated with specific taxa during the first stages of decomposition which are dominated by bacteria. Through best-fitting multiple linear regression models, the synthesis of acetic acid, indole and phenol could be linked to the activity of Enterobacteriaceae, Tissierellaceae and Xanthomonadaceae, respectively. These conclusions are also commensurate with the metabolism described for the dominant taxa identified for these families. The predictable nature of in situ synthesis of cadaveric volatile organic compounds by epinecrotic bacteria provides a new basis for future chemical ecology and forensic studies.

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.…”

“…See Pascual et al. and Eckert et al. for recent investigations into the relationships between microorganisms and VOCs.…”

“…This use of sulfur is probably related to the release of volatile organic compounds (VOCs) commonly associated with decomposing remains. See Pascual et al (39) and Eckert et al (40) for recent investigations into the relationships between microorganisms and VOCs.…”

Experimental evaluation on the applicability of necrobiome analysis in forensic veterinary science

“…Within Proteobacteria, Pseudomonadaceae represented the highest fraction in the active decay stage while Xanthomonadaceae was the major taxon during the late stage of the decomposition. In particular, the increase in Xanthomonadaceae over time on skin and grave soil was already observed by using mouse and swine carcasses (Metcalf et al, 2013;Pascual et al, 2017). This datum, as in accordance with what Pechal observed on pig carcasses (Pechal et al, 2014), strengthens the hypothesis that the Xanthomonadaceae family may be a key contributor to the general process of the decomposition regardless the host (Hyde et al, 2015).…”

“…The selection of an animal model depends on some factors including availability, cost, ease of handling, investigator familiarity, and anatomical/functional similarity to humans. In accordance to the latter factor, mainly swine carcasses, Sus scrofa Linnaeus, 1758, have been largely used (Carter et al, ; Pascual et al, ; Pechal et al, ). It is in fact well established that swines and pigs show a high anatomical and physiological similarity to humans and have the closest pattern decomposition pattern to them (Catts & Goff, ).…”