Effects of microbial DNA on human DNA profiles generated using the PowerPlex® 16 HS system

Effects of chemical & biological warfare agent decontaminants on trace survival: Impact on DNA profiling from blood and saliva

Forensic investigations following incidents involving chemical or biological agents present considerable challenges. Understanding the possibilities and limitations can aid in determining the most suitable procedures and enhancing the recovery of useful traces in these complex situations. This work complements previously published results on the effects of decontaminants on fingermarks deposited on glass. Identifying the perpetrators can be crucial, and DNA analysis remains a cornerstone in this regard. In this study, we investigated the ability to obtain usable DNA profiles from blood and saliva (pure and diluted) exposed to 16 different decontamination methods. Both DNA quantitation and DNA profiling were considered to assess the outcomes. The results revealed considerable variability but indicated that biological agents' decontaminants hindered DNA profiling post-decontamination to a greater extent than decontaminants aimed for chemical agents. Chlorine-based decontaminants also globally had a deleterious impact on DNA profiling. Powder decontaminants such as Fast-Act, CHpowder, and the liquid decontaminants GDS2000 did not affect DNA profiling.

Analysis of Microbial Communities: An Emerging Tool in Forensic Sciences

The objective of forensic sciences is to find clues in a crime scene in order to reconstruct the scenario. Classical samples include DNA or fingerprints, but both have inherent limitations and can be uninformative. Another type of sample has emerged recently in the form of the microbiome. Supported by the Human Microbiome Project, the characteristics of the microbial communities provide real potential in forensics. They are highly specific and can be used to differentiate and classify the originating body site of a human biological trace. Skin microbiota is also highly specific and different between individuals, leading to its possibility as an identification tool. By extension, the possibilities of the microbial communities to be deposited on everyday objects has also been explored. Other uses include the determination of the post-mortem interval or the analysis of soil communities. One challenge is that the microbiome changes over time and can be influenced by many environmental and lifestyle factors. This review offers an overview of the main methods and applications to demonstrate the benefit of the microbiome to provide forensically relevant information.

Next generation sequencing of STR artifacts produced from historical bone samples

STR artifacts are commonly observed in electrophoretic data and can complicate interpretation of the profiles produced. Even when a consensus approach is applied, reproducible artifacts have the potential to convolute the analysis. DNA obtained from historical bone samples is often heavily degraded and damaged, requiring the use of more sensitive procedures to increase allele recovery. Additionally, skeletal remains exposed to environmental conditions may be afflicted with microbial DNA contamination that cross-reacts with the primers during short tandem repeat (STR) multiplex amplification. STR artifacts manifested as a result of these circumstances can be sourced and characterized using new sequencing technologies to potentially ease the analysis burden. For this study, PCR product from 17 low-quality bone samples exhibiting reproducible autosomal and Y-chromosomal STR (Y-STR) artifacts in capillary electrophoresis (CE) data were sequenced with next generation sequencing (NGS). Sequenced reads were bioinformatically sorted using STRait Razor to determine the authenticity of alleles and confirm the profile generated by CE. Sequence data from the PCR products and a subset of the associated extracts were further analyzed with Kaiju to classify the microbial species present and identify potential sources of artifact peaks. A suspected Y-STR artifact was similar in sequence to Pseudomonas sp. BAY1663, a species ubiquitously found in soil. Regions of homology were observed between the Pseudomonas genome and the presumed primer binding locations for Y-STRs included in the AmpFlSTR Y-Filer STR kit. Characterization of such supposed artifact peaks may aid in interpretation of CE data and ultimately lead to increased confidence in the reported results.