Microbial Forensics

Forensic DNA analysis has been used predominantly for comparison, either directly or indirectly, of crime scene evidence and known reference samples from human suspects in a variety of situations, such as analyzing a biospecimen(s) from a crime scene, identifying unidentified cadavers (or other human remains) in a postmortem setting, or kinship testing. The field of forensic genetics has recently expanded from its original focus on human samples to more holistic methods of characterization of the source(s) of biological samples. This progression has been motivated in part by technological advancements, from targeted PCR-based methods to higher throughput DNA sequencing methods, with concomitant bioinformatics to support the increased data output. One of the new areas in forensic genetics facilitating the expansion of forensic genomics is the field of microbial forensics. Microbial forensics involves bioterrorism, biocrime, human identification, determining postmortem interval, human geolocation, and body fluid identification.

A walk on the dirt: soil microbial forensics from ecological theory to the crime lab

ABSTRACT Forensics aims at using physical evidence to solve investigations with science-based principles, thus operating within a theoretical framework. This however is often rather weak, the exception being DNA-based human forensics that is well anchored in theory. Soil is a most commonly encountered, easily and unknowingly transferred evidence but it is seldom employed as soil analyses require extensive expertise. In contrast, comparative analyses of soil bacterial communities using nucleic acid technologies can efficiently and precisely locate the origin of forensic soil traces. However, this application is still in its infancy, and is very rarely used. We posit that understanding the theoretical bases and limitations of their uses is essential for soil microbial forensics to be judiciously implemented. Accordingly, we review the ecological theory and experimental evidence explaining differences between soil microbial communities, i.e. the generation of beta diversity, and propose to integrate a bottom-up approach of interactions at the microscale, reflecting historical contingencies with top-down mechanisms driven by the geographic template, providing a potential explanation as to why bacterial communities map according to soil types. Finally, we delimit the use of soil microbial forensics based on the present technologies and ecological knowledge, and propose possible venues to remove existing bottlenecks.