Dr Bucheli and Dr Lynne
Knowledge about relative abundances of particular insects and bacteria during decomposition could help in tracking the stages of cadaver decomposition lead to more accurate methods to estimate the time since death. Incorporating precise measurements of additional ecosystem components surrounding cadavers and aid in refinement of those estimations.
Despite the integral roles of bacteria and insects in decomposition, very little is understood regarding the microbial basis of decomposition and bacteria may help to recruit or repel insects to or from a corpse. By analyzing the microbial communities involved in every stage of cadaver decomposition, we can gain a more precise understanding of the overall process. Knowing the identity and succession of those bacterial communities not only provides insights into the overall process but can also aid in determining the postmortem interval when dealing with unidentified remains. Preliminary results indicate common trends in bacterial succession. For example, the bacterial community structures are variable at the outset and before purge for all body sites. At bloat and purge and until tissues begin to dehydrate or are removed, bacteria associated with flies are common. After cadavers dehydrate to form skeletons, bacteria associated with soil are among the most common at most body sites. These trends also seem to be seasonally specific. For example, during winter when insect activity is minimal, fly-associated bacteria are absent. We do not yet know whether these bacteria are mere markers of insect activity or actively facilitate decomposition.
In our research with Jessica Metcalf at Colorado State University, we are using molecular identification techniques to catalogue how bacterial diversity changes through time as cadavers decompose. We use two specific approaches, with one that we call “inside out,” following how bacteria that are present internally change with time and whether that affects the external microbiome as a body purges. The second approach, “outside in,” looks at whether the microbiome along the external surface of cadavers changes in a predictable way and whether there are other external sources or sinks affecting that microbiome. Additionally, we are interested in understanding how abiotic factors influence these microbial successions. We are also looking at microbial communities in the bones and soil beneath cadavers, in collaboration with Rob Knight at the University of California, San Diego, Jessica Metcalf at the University of Colorado, Boulder, and David Carter at Chaminade University in Honolulu, Hawaii.