The potential use of bacterial community succession in forensics as described by high throughput metagenomic sequencing

Authors: PECHAL, JENNIFER - University Of Dayton; Crippen, Tawni - Tc; BENBOW, M - University Of Dayton; TARONE, AARON - Texas A&M University; DOWD, SCOT - Molecular Research Lp (MR DNA); TOMBERLIN, JEFFERY - Texas A&M University

Submitted to: International Journal of Legal Medicine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/7/2013
Publication Date: 6/10/2013
Publication URL: http://handle.nal.usda.gov/10113/58710
Citation: Pechal, J.L., Crippen, T.L., Benbow, M.E., Tarone, A.M., Dowd, S., Tomberlin, J.K. 2013. The potential use of bacterial community succession in forensics as described by high throughput metagenomic sequencing. International Journal of Legal Medicine. 128:193-205.

Interpretive Summary: Decomposition studies often focus on data that can be seen with the naked eye, such as insects and animal scavengers, and ignore the bacterial communities present. We documented the bacterial species present during decomposition of animal carrion. High throughput genetic sequence identification was used to describe abundance and types of bacteria at specific time points during the decay process. This information is important to understanding locations and movement of bacteria and bacterial pathogens on animal carcasses. The bacterial community showed differences in composition and abundance over time. A model was developed using this genetic technique that provides a framework for standard operating procedure of how to use high throughput sequencing as a potential new tool to document and identify bacterial communities during decomposition. This tool is important to animal production operations to monitor the presence and movement of pathogens during normal operations and during mass die-offs associated with man-made and natural disasters and disease epidemics.

Technical Abstract: Decomposition studies primarily focus on the gross observable data that can be seen with the naked eye, such as insects or vertebrate scavengers, with little regard for what might be occurring at the microorganism community level. Here we document the 'necrobiome' or the community of species associated with the decomposition of remains and specifically analyze 'epinecrotic' bacterial community succession throughout decomposition of vertebrate carrion. Pyrosequencing was used to detect and identify bacterial community abundance patterns that described discrete time points of the decomposition process by identifying bacterial taxa important for estimating accumulated degree hours, which was used as a surrogate for minimum postmortem interval estimates. The bacterial community structure demonstrated significant differences in taxon richness and relative abundance patterns through the decomposition process at both phylum and family taxonomic classification levels. There was a significant negative linear relationship for overall phylum and family taxon richness. Additionally, a model was developed using high throughput sequencing of carrion associated bacterial communities on vertebrate remains that explained 94.4% of the time since placement of remains in the field. We provide a framework and standard operating procedure of how this novel approach of using high throughput sequencing has remarkable potential as a new forensic tool. Documenting and identifying differences in bacterial communities is key to advancing knowledge of the carrion necrobiome and its applicability in forensic science.