Quantifying the relative contributions of bacterial and fungal communities to carcass decomposition using a...

Carcass microbial decomposition plays a vital role in global elemental cycling. However, bacterial and fungal absolute abundance dynamics, as well as their contributions to carcass decomposition, remain unclear. Here, the questions were investigated through quantitative microbiome profiling (QMP) and metabolomics. Within the first 14 days postmortem, microbial copies in grave soil and tissue increased by several orders of magnitude. Comparison of QMP with relative microbiome profiling (RMP) revealed strikingly different, even opposing successional trends for major phyla. Bacteria drove more metabolite variation than fungi in the decomposition. Co-occurrence networks revealed that key bacterial and fungal decomposers formed two distinct modules that were highly interconnected and significantly associated with carcass-derived metabolites, suggesting a synergistic relationship in the breakdown of organic matter. Notably, using QMP did not substantially enhance the accuracy of postmortem interval estimation. Collectively, our findings provide critical insights into microbial ecological dynamics during carcass decomposition.