Microbial soil community analyses for forensic science: Application to a blind test.

Area of Science:

• Microbial Ecology
• Forensic Science
• Soil Science

Background:

• Soil's unique characteristics offer forensic value for tracing sample origins.
• Current forensic applications of soil analysis are limited, particularly concerning microbial communities.
• Bacterial communities in soil present a promising, yet underexplored, forensic tool.

Purpose of the Study:

• To evaluate the forensic potential of soil bacterial communities for determining sample origin.
• To assess the discriminating power of Ribosomal Intergenic Spacer Analysis (RISA) and 16S rRNA gene sequencing.
• To determine if combined molecular techniques can identify mixed soil origins.

Main Methods:

• A blind test was conducted using soil samples from a mock crime scene, an alibi site, and mixtures.
• Two molecular techniques were employed: Ribosomal Intergenic Spacer Analysis (RISA) and 16S rRNA gene sequencing (Illumina Miseq).
• Bacterial community profiles were analyzed to differentiate soil samples based on their origin.

Main Results:

• Both RISA and 16S rRNA gene sequencing effectively discriminated between soils from distinct single sources.
• A combination of both techniques was essential to accurately identify a 50:50 mixture of soil samples.
• The study demonstrated the high discriminatory power of soil microbial communities.

Conclusions:

• Microbial ecology methodologies applied to soil offer a valuable forensic tool.
• Combining RISA and 16S rRNA gene sequencing enhances the ability to trace soil origins, including mixtures.
• This approach holds significant potential for improving forensic investigations through soil analysis.