Environmental microbiota from substrate may interfere with microbiome-based identification of forensically relevant...

Area of Science:

• Forensic microbiology
• Microbiome analysis
• Molecular biology

Background:

• The microbiome offers potential for identifying body fluids at crime scenes.
• Substrate microbes can impact microbiome-based body fluid identification, but this effect is poorly understood.

Purpose of the Study:

• To investigate the influence of different substrates on the microbiome of deposited body fluids.
• To assess the effectiveness of decontamination methods in improving body fluid identification from crime scene samples.

Main Methods:

• Five body fluids (peripheral blood, menstrual blood, nasal secretions, saliva, semen) were deposited on sterile swabs, bedspreads, and floors.
• Microbial communities were analyzed using 16S rRNA gene amplicon sequencing.
• FEAST analysis and PERMANOVA were employed to assess microbial community composition and substrate/body fluid influence.
• MicroDecon was used for substrate microbial decontamination.

Main Results:

• Microbial communities clustered by body fluid type on sterile swabs but were significantly altered by bedspread and floor substrates.
• Substrate microbes influenced mock body fluid samples, with varying effects depending on the body fluid type.
• PERMANOVA indicated substrate explained more variance than body fluid type initially (R² = 0.211 vs. 0.152).
• After decontamination, body fluid type explained more variance (R² = 0.240) than the substrate (R² = 0.108).

Conclusions:

• Environmental microbiota from substrates interfere with microbiome-based identification of forensically relevant body fluids.
• Decontamination strategies can mitigate substrate effects, enhancing the ability to distinguish between body fluid types.
• This study provides valuable insights for applying microbiome-based stain analysis in forensic investigations.