Microbial community succession of gravesoils at SHSU 2015
During vertebrate decomposition, a purge of nutrient-rich fluids enters the surrounding soil producing a localized nutrient hotspot. The composition of microbial communities at the soil surface has been shown to predictably change in response to this influx of decomposition fluids over time. However, the depth to which these compositional changes permeate the soil near a decomposing human cadaver and which microbial members exhibit responses to aboveground decomposition both represent significant knowledge gaps. In this study, we longitudinally sampled forest soils adjacent to decomposing human cadavers and from nearby control sites in 2 cm increments to a depth of 10 cm. Soil samples were collected during purge, post purge, and the dry remains stage of decomposition over three seasons at Sam Houston State University's Southeast Texas Applied Forensic Science Facility. We detected microbial community responses in the upper 0–4 cm of soils adjacent to decomposition fluids, including several bacterial genera that significantly increased in response to decomposition. Microbial community diversity decreased and community composition became increasingly different in comparison to the nearby control soils as decomposition progressed. We observed a more limited, yet still detectable response in the lower 6 – 10 cm of soil. In addition to improving our understanding of decomposition ecology, we anticipate that incorporating these findings into forensic investigations could help strengthen postmortem interval model estimation and better inform investigative sampling practices.
During vertebrate decomposition, a purge of nutrient-rich fluids enters the surrounding soil producing a localized nutrient hotspot. The composition of microbial communities at the soil surface has been shown to predictably change in response to this influx of decomposition fluids over time. However, the depth to which these compositional changes permeate the soil near a decomposing human cadaver and which microbial members exhibit responses to aboveground decomposition both represent significant knowledge gaps. In this study, we longitudinally sampled forest soils adjacent to decomposing human cadavers and from nearby control sites in 2 cm increments to a depth of 10 cm. Soil samples were collected during purge, post purge, and the dry remains stage of decomposition over three seasons at Sam Houston State University's Southeast Texas Applied Forensic Science Facility. We detected microbial community responses in the upper 0–4 cm of soils adjacent to decomposition fluids, including several bacterial genera that significantly increased in response to decomposition. Microbial community diversity decreased and community composition became increasingly different in comparison to the nearby control soils as decomposition progressed. We observed a more limited, yet still detectable response in the lower 6 – 10 cm of soil. In addition to improving our understanding of decomposition ecology, we anticipate that incorporating these findings into forensic investigations could help strengthen postmortem interval model estimation and better inform investigative sampling practices.
University of California San Diego Microbiome Initiative