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The Impact of Submersion on the Quantification of Host and Bacterial DNA

Grace Sprouse, Depts. of Forensic Science and Chemistry, with Dr. Catherine Connon, Dept. of Forensic Science and Dr. Baneshwar Singh, Dept. of Forensic Science

Microorganisms, which contribute to carrion decomposition, can be used as a clock to estimate time since death. There has been an increase in the amount of studies looking into how bacteria can be used to estimate time since death. Much of this research has been aimed at examining how microorganism communities can be used to determine post mortem interval (PMI) in land environments, for example, research completed by Finley et all1, which focused on how microorganism communities differ on corpses and in the soil surrounding the body. Finley et all1 research was used to see how these quantities can be used to determine PMI. However, the comparison between 16S rDNA and nDNA has not been explored. Changes in bacterial DNA quantity may inform researchers on feasibility of using bacteria on remains to estimate the postmortem interval (PMI) and postmortem submersion interval (PMSI). It could also provide insight regarding bacteria: host nDNA ratio, guiding decisions on best methods for victim ID (i.e., microbe based PMSI estimation or DNA profile development). Therefore, this research sought to compare bacterial DNA (16S rDNA) to host nuclear DNA (nDNA) recovered from long-term submerged skeletal elements (e.g., rib and scapula) using two different extraction methods (e.g., organic-phenol chloroform and solid-phase). Using 10” x 10” cages, each containing five ribs and scapulae, samples were submerged in a freshwater lake (e.g., Henley Lake) and river (e.g., James River). Approximately ca. 250 accumulated degree days (ADD), one cage was collected, totaling nineteen lake and twenty-four river collections.

The resulting 364 samples underwent DNA extraction (e.g., organic phenol-chloroform and ChargeSwitch®) before being analyzed via agarose gel electrophoresis (1.0% agarose gel). Gel visualization was performed to evaluate the separation of DNA bands and assess the quality of the extraction method used on each sample. In preparation for Real-Time qPCR quantification, standard curves were performed. Using the ABI 7500, each sample will be quantified twice, once using bacterial primers focusing on variable region 4 of 16S rDNA and once utilizing FH1733 porcine nuclear primers2. This section of the research will continue when the university reopens.

Publication Date


Faculty Advisor/Mentor

Catherine Connon, Ph.D.

Faculty Advisor/Mentor

Baneshwar Singh, Ph.D.


Virginia Commonwealth University. Undergraduate Research Opportunities Program

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VCU Undergraduate Research Posters


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The Impact of Submersion on the Quantification of Host and Bacterial DNA