Responses of skin and salivary microbiome to different environmental exposures

Forensic microbiology allows identification by microbiome analysis when human DNA analysis is limited. However, microbiome-based approaches have not been widely used in forensic medicine. The spatial and temporal stability of microbial communities in response to environmental exposures represents a serious challenge. This study investigates the dynamics of skin and saliva microbial markers in response to environmental exposure to advance their forensic applicability. We selected 8 characteristic microorganisms (Finegoldia magna, Corynebacterium tuberculostearicum, Cutibacterium acnes for skin; Haemophilus parainfluenzae, Streptococcus oralis, Prevotella melaninogenica for saliva; Achromobacter, Pseudomonas as environmental markers) and developed two multiplex amplification systems for capillary electrophoresis detection. A longitudinal exposure model (0-120 days) under controlled indoor and dry environment was applied to 420 skin and saliva samples from 10 subjects. Saliva samples exhibited significant microbial community shifts between environments (R² = 0.4137). Dry environment preserved community structure better, evidenced by delayed inflection points in markers' proportions and stronger clustering in PCoA. Redundancy analysis correlated microbial markers with temperature and humidity, and this correlation varied. The microbial markers remained detectable after 120 days of environmental exposure and were able to provide information on community characteristics and deposition time. This study explored the effects of environment and time on microbial communities and the response patterns of microbial markers to temperature and humidity. It is expected to provide help for forensic microbial research related to environmental exposure.