Abstract
Microorganisms play a vital role in the decomposition of vertebrate remains in natural nutrient cycling, and the postmortem microbial succession patterns during decomposition remain unclear. The present study used hierarchical clustering based on Manhattan distances to analyze the similarities and differences among postmortem intestinal microbial succession patterns based on microbial 16S rDNA sequences in a mouse decomposition model. Based on the similarity, seven different classes of succession patterns were obtained. Generally, the normal intestinal flora in the cecum was gradually decreased with changes in the living conditions after death, while some facultative anaerobes and obligate anaerobes grew and multiplied upon oxygen consumption. Furthermore, a random forest regression model was developed to predict the postmortem interval based on the microbial succession trend dataset. The model demonstrated a mean absolute error of 20.01h and a squared correlation coefficient of 0.95 during 15-day decomposition. Lactobacillus, Dubosiella, Enterococcus, and the Lachnospiraceae NK4A136 group were considered significant biomarkers for this model according to the ranked list. The present study explored microbial succession patterns in terms of relative abundances and variety, aiding in the prediction of postmortem intervals and offering some information on microbial behaviors in decomposition ecology.
Highlights
As a key aspect of the material cycle and energy flow of the ecosystem, the decomposition of vertebrate remains is one of the main processes involved in maintaining ecosystem functions
Samples with library sizes close to, or larger than, 3000 reads showed convergence in their sampling effort curves. These high-quality sequences were assigned to a total of 5,099 operational taxonomic units (OTUs) by the UPARSE pipeline using a threshold of 97% identity
The microbial community was dominated by OTUs with the Firmicutes (Fig. 1d) affiliated within the Lactobacillaceae
Summary
As a key aspect of the material cycle and energy flow of the ecosystem, the decomposition of vertebrate remains is one of the main processes involved in maintaining ecosystem functions. A lack of oxygen results in cell autolysis, and tissue breakdown, releasing cellular components and macromolecules. These nutrients are subsequently metabolized by predominately microbial communities, those concentrated in the gastrointestinal tract. The number of studies of the dynamic succession patterns in these microbial communities is relatively small, but these studies may facilitate estimation of the postmortem interval (PMI) in forensic investigations and improve understanding of the mechanisms governing succession processes during decomposition to accelerate decomposition, facilitate nutrition recycling, and reduce environmental pollution
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