Characterization of the soil microbial community associated with the decomposition of a swine carcass

Abstract

Identification of bacterial species and their metabolic activity may be useful in differentiating soil samples associated with forensic analyses of large animal carcasses. In this preliminary study, lipolytic and proetolytic soil bacteria were enumerated over the time course of decomposition of a swine carcass. A 60-kg pig was used because it resembles a human body in its fat distribution and cover of hair. Soil core-samples (grave-soil) were taken underneath the carcass every three days until day 15, and then sampled on days 28, 43, 57, and 71 between September and December 2008. Results indicated that lipolytic bacterial counts were initially the lowest at day 0 (before exposure) and increased to their highest between days 9 and 12 (active decomposition); they then decreased and leveled at days 15 through 71. Conversely, the proteolytic bacterial counts initially were the highest at day 0, slowly decreased at days 3 (fresh) and 6 (bloat) with a rapid decline at day 9 (active) followed by a second major decline at day 28 (advanced); they then leveled through the remaining time period. Of the 33 isolates that could be identified, 18 were in the genus Acinetobacter. The qPCR results using Group I lipase-specific primers followed a similar pattern as the lipolytic CFU observed.