Department of Integrative Biology, Michigan State University, East Lansing, Michigan, USA.
Department of Entomology, Michigan State University, East Lansing, Michigan, USA.
J Forensic Sci. 2022 Jul;67(4):1565-1578. doi: 10.1111/1556-4029.15036. Epub 2022 Mar 29.
After death, microbes (including bacteria and fungi) colonize carrion from a variety of sources during the decomposition process. The predictable succession of microbes could be useful for forensics, such as postmortem submersion interval estimation (PMSI) for aquatic deaths. However, gaps exist in our understanding of microbial succession on submerged bone, particularly regarding longer-term decomposition (>1 year), fungal composition, and differences between internal and external microbial communities. To further explore this potential forensic tool, we described the postmortem microbial communities (bacteria and fungi) on and within submerged bones using targeted amplicon sequencing. We hypothesized predictable successional patterns of microbial colonization would be detected on the surface and within submerged bones, which would eventually converge to a similar microbial community. To best replicate forensic contexts, we sampled bones from replicate swine (Sus scrofa domesticus) carcasses submerged in a freshwater pond, every three months for nearly two years. Microbial bone (internal vs. external) community structure (taxa abundance and diversity) of bones differed for both bacteria and fungi, but internal and external communities did not converge to a similar structure. PMSI estimation models built with random forest regression of postmortem microbiomes were highly accurate (>80% variation explained in PMSI) and showed promise for forensic purposes. Overall, we provide further evidence that internal and external bone microbial communities submerged in an aquatic habitat are distinct and each community undergoes predictable succession, demonstrating potential utility in forensics for modeling PMSI in unattended deaths and/or cold cases.
死亡后，在分解过程中，来自各种来源的微生物（包括细菌和真菌）会在尸体上定殖。微生物的可预测演替可能对法医学有用，例如用于水生死亡的死后浸没时间估计（PMSI）。然而，我们对水下骨骼上微生物演替的理解存在空白，特别是在更长期的分解（>1 年）、真菌组成以及内部和外部微生物群落之间的差异方面。为了进一步探索这种潜在的法医工具，我们使用靶向扩增子测序描述了水下骨骼上和内部的死后微生物群落（细菌和真菌）。我们假设可以在表面和水下骨骼上检测到微生物定殖的可预测演替模式，这些模式最终将收敛到类似的微生物群落。为了最好地复制法医环境，我们从重复的猪（Sus scrofa domesticus）尸体上采样，将这些尸体浸泡在淡水池塘中，每三个月采样一次，持续了将近两年。细菌和真菌的骨骼内部（内部与外部）微生物群落结构（分类群丰度和多样性）存在差异，但内部和外部群落并未收敛到相似的结构。基于死后微生物组的随机森林回归构建的 PMSI 估计模型具有高度准确性（>80%的 PMSI 变化得到解释），并且有望用于法医目的。总的来说，我们提供了进一步的证据，表明在水生环境中浸泡的内部和外部骨骼微生物群落是不同的，每个群落都经历了可预测的演替，这表明在法医中具有建模无人看管死亡和/或冷案中的 PMSI 的潜在用途。
