The Microbiome and Volatile Organic Compounds Reflect the State of Decomposition in an Indoor Environment

Abstract

Because of the variety of factors that can affect the decomposition process, it can be difficult to determine the post-mortem interval (PMI). The process is highly dependent on microbial activity, and volatile organic compounds (VOCs) are a by-product of this activity. Given both have been proposed to assist in PMI determination, a deeper understanding of this relationship is needed. The current study investigates the temporal evolution of the microbiome and VOC profile of a decomposing human analog (swine) in a controlled, indoor environment. Microbial communities and VOCs were sampled at six-time points, up to the active decay phase. Sampling locations included the abdominal area, anus, right ear canal, and right nostril. Bacterial communities were found to significantly change during decomposition (p-value < 0.001), and communities evolved differently based on sampling location. The families Moraxellaceae, Planococcaceae, Lactobacillaceae, and Staphylococcaceae drove these community shifts. From random forest analysis, the nostril sampling location was determined to be the best location to predict stage of decomposition. Individual VOCs exhibited large temporal shifts through decomposition stage in contrast to smaller shifts when evaluated based on functional groups. Finally, pairwise linear regression models between abdominal area bacteria and selected VOCs were assessed; Planococcaceae and Tissierellaceae were significantly correlated to indole. Overall, this study provides an exploratory analysis to support the connection between the microbiome, VOCs, and their relationship throughout decomposition. ImportanceThis research provides valuable insight into the complex process of decomposition, which is pertinent to forensic death investigations. The temporal evolution of both the microbiome and volatile organic compounds (VOCs) were characterized as a function of stage of decomposition and evaluated their interdependency upon one another. In turn, this information may assist in determining time since death, and fill a knowledge gap about VOC-bacteria associations during the decay process.