Microbial succession in human tissues postmortem: insights from 2bRAD-M sequencing

Microbial communities play a crucial role in decomposition, yet their patterns in human tissues remain underexplored. Most previous research has often focused on animal models such as mice and swine, with limited studies on human samples, primarily targeting specific environments like the gut and skin. Consequently, gaps persist in understanding postmortem microbial dynamics within internal human organs. The 2bRAD-M sequencing technology offers a powerful approach for human thanatomicrobiome research, overcoming key limitations of 16S rRNA and metagenomic sequencing methods. In this study, we used 2bRAD-M to profile microbial succession across seven human tissues-heart, liver, spleen, lung, kidney, calf muscle, and gut-at various postmortem intervals (PMIs). Significant variations in microbial community composition were observed across organs and decomposition stages, with Proteobacteria dominating early and Firmicutes later. A comparison of frozen and unfrozen cadavers (PMI 1-7 days) revealed divergent microbial shifts in the liver and spleen, while other tissues exhibited limited variation. These findings highlight complex, organ-specific microbial trajectories and suggest that microbial signatures could serve as biomarkers for PMI estimation. This research deepens our understanding of the microbial succession within internal human organs postmortem and contributes to elucidating the identity and role of microorganisms in human decomposition.IMPORTANCEHumans host a diverse array of microbial communities that play a crucial role in the decomposition process after death. Understanding these postmortem microbial dynamics is essential, as they offer valuable insights into the progression of decomposition with significant implications for forensic science. The role of microorganisms in corpse decomposition has gained increasing attention in both forensic and ecological research, but studies in this area remain in their early stages, requiring further in-depth exploration. This work pioneers the use of 2bRAD-M sequencing to investigate microbial changes across various human organs over increasing postmortem intervals. By enhancing knowledge of postmortem microbiota dynamics, the study contributes to refining and improving the accuracy of forensic methodologies.