Assessment of microbial DNA extraction methods of cadaver soil samples for criminal investigations

<p>Gravesoil beneath decomposing cadavers undergoes substantial biochemical changes that have the potential to aid in PMI estimation and identification of clandestine gravesites. The use of DNA extraction methods is necessary for culture-independent downstream molecular applications such as PCR and next-generation sequencing. In this study, a comparison of four methods was performed for cadaver-soil collected beneath the heads and feet of 11 cadavers decaying in a natural setting. The four methods isolated 3.6–263 ng/μl of genomic DNA as determined by optical density analysis. The purity of the extracted DNA according to A_260/280 and A_260/230 ratios was determined. The A_260/280 and A_260/230 ratios were 1.24–1.97 and 0.27–2.12, respectively. The optical density at 320 nm was measured for humic acid quantification of the lysates from the method that provided the most efficient removal of humic acid. The results demonstrated that this method provided a 98% reduction of humic acid. PCR of 16S rRNA genes followed by gel electrophoresis was performed. The statistical analysis revealed a significant correlation between the yields and days on/in the soil using a phenol-chloroform method for soil collected at the head and feet. No earlier published work has extensively elucidated the efficacy of DNA extraction methods for DNA obtained from cadaver-soil.