Abstract
Genomic studies have estimated there are approximately 103–106 bacterial species per gram of soil. The microbial species found in soil associated with decomposing human remains (gravesoil) have been investigated and recognized as potential molecular determinants for estimates of time since death. The nascent era of high-throughput amplicon sequencing of the conserved 16S ribosomal RNA (rRNA) gene region of gravesoil microbes is allowing research to expand beyond more subjective empirical methods used in forensic microbiology. The goal of the present study was to evaluate microbial communities and identify taxonomic signatures associated with the gravesoil human cadavers. Using 16S rRNA gene amplicon-based sequencing, soil microbial communities were surveyed from 18 cadavers placed on the surface or buried that were allowed to decompose over a range of decomposition time periods (3–303 days). Surface soil microbial communities showed a decreasing trend in taxon richness, diversity, and evenness over decomposition, while buried cadaver-soil microbial communities demonstrated increasing taxon richness, consistent diversity, and decreasing evenness. The results show that ubiquitous Proteobacteria was confirmed as the most abundant phylum in all gravesoil samples. Surface cadaver-soil communities demonstrated a decrease in Acidobacteria and an increase in Firmicutes relative abundance over decomposition, while buried soil communities were consistent in their community composition throughout decomposition. Better understanding of microbial community structure and its shifts over time may be important for advancing general knowledge of decomposition soil ecology and its potential use during forensic investigations.
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Acknowledgments
The authors thank Daniel J. Wescott and Sophia R. Mavroudas of the FARF at Texas State University for use of their facilities and support from their staff. We also thank the donors to the FARF whose generous gifts make this type of research feasible. Many thanks are extended to Vida Dennis for the very helpful comments during the preparation of this manuscript. This work was supported by the National Science Foundation (NSF) grants HRD 1401075, 1432991, 1433004 and discretionary funds of Michigan State University to MEB.
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Sheree J. Finley and Jennifer L. Pechal contributed equally to this work.
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Finley, S.J., Pechal, J.L., Benbow, M.E. et al. Microbial Signatures of Cadaver Gravesoil During Decomposition. Microb Ecol 71, 524–529 (2016). https://doi.org/10.1007/s00248-015-0725-1
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DOI: https://doi.org/10.1007/s00248-015-0725-1