Sex-specific postmortem microbiome dynamics in mice: implications for death definitions.

Gut microbes form a complex and dynamic symbiotic relationship with their host. However, the microbial response during the early stages following host death remains largely uncharacterized. In this study, we employed a mouse model to systematically characterize the postmortem response of the intestinal microbiota, and analyzed the dynamic changes in microbial composition during the early stages after death in both male and female mice (at 0, 0.5, 2, 6, 12, and 24 h postmortem). Our findings reveal that sex-dimorphic shifts in microbiome composition occur as early as 2 h postmortem. Male mice exhibited increased functional redundancy and delayed community restructuring, whereas female mice displayed earlier community shifts. These sex-specific patterns were accompanied by differences in metabolic pathway activity and biomarker taxa. Notably, the observed retention of regulatory capacity by intestinal microbes after host death offers a novel perspective on the conceptualization of death itself. We propose the term "ecological death" to describe the irreversible collapse of the host-associated microbial ecosystem following death, marking a critical transition in the functional and structural integrity of the intestinal microbiota.