Department of Forensic Science, Virginia Commonwealth University, Richmond, VA, United States; Visiting Scientist Program, Oak Ridge Institute for Science and Education, Stafford, VA, United States.
Department of Forensic Science, Virginia Commonwealth University, Richmond, VA, United States; Department of Chemistry, University of Virginia, Charlottesville, VA, United States.
Forensic Sci Int. 2019 Sep;302:109838. doi: 10.1016/j.forsciint.2019.05.054. Epub 2019 Jun 3.
Recent, short-term studies on porcine and human models (albeit with few replicates) demonstrated that the succession of the microbial community of remains may be used to estimate time since death. Using a porcine model (N=6) over an extended period of time (1703 ADD, or two months), this study characterized the eukaryote community of decomposing remains. Skin microbial samples were collected from the torso of each set of remains every day during the first week, on alternate days during the second week, and once a week for the remainder of the 60-day period; all collection intervals were recorded in accumulated degree days (ADD). The eukaryote community of each sample was determined using 18S ribosomal DNA (rDNA) MiSeq high throughput sequencing; data were analyzed in the Mothur pipeline (v1.39.5) and in IBM SPSS and R statistical packages. The relative abundance of eukaryote taxa across ADD/Days and an Analysis of Molecular Variance (AMOVA) indicated similarities between sequential ADD/Days, but significant differences in the eukaryote communities as broad stage 'milestones' of decomposition were reached. Fresh remains (0-57 ADD/0-2 Days; exhibiting a total body score (TBS) of 0-10) were characterized by the combined presence of Saccharomycetaceae, Debaryomycetaceae, Trichosporonaceae, Rhabditida, and Trichostomatia. During bloat and active decay (87-209 ADD/3-7 Days; exhibiting TBS of 11-20), Diptera was the most abundant eukaryotic taxa. During advanced decay stage (267-448 ADD/9-15 Days; exhibiting TBS of 21-25), Rhabditida was the most dominant eukaryote. Dry/skeletal remains (734-1703 ADD/26-61 Days; TBS≥26) were dominated by fungal families Dipodascaceae, Debaryomycetaceae, Trichosporonaceae, and Sporidiobolaceae. Using the family-level eukaryote taxonomic data for the entire study, random forest modelling explained 89.58% of the variation in ADD/Days, with a root mean square error (RMSE) of 177.55 ADD (≈6 days). Overall, these results highlight the importance of the microbial eukaryote community during the process of decomposition and in estimation of PMI.
最近，在猪和人类模型上进行的短期研究（尽管重复次数较少）表明，遗体微生物群落的演替可用于估计死亡时间。本研究使用猪模型（N=6），在较长时间（1703 个度日或两个月）内，对分解遗体的真核生物群落进行了特征描述。在第一周的每一天，从每具遗体的躯干上采集皮肤微生物样本，在第二周的每隔一天采集一次，在接下来的 60 天内每周采集一次；所有采集间隔均以累积度日（ADD）记录。使用 18S 核糖体 DNA（rDNA）MiSeq 高通量测序确定每个样本的真核生物群落；数据在 Mothur 管道（v1.39.5）以及 IBM SPSS 和 R 统计软件包中进行分析。根据 ADD/天数和分子方差分析（AMOVA）分析的真核生物分类群的相对丰度表明，随着分解的广泛阶段“里程碑”的出现，连续的 ADD/天数之间存在相似性，但真核生物群落存在显著差异。新鲜遗体（0-57 ADD/0-2 天；总尸检评分（TBS）为 0-10）的特征是 Saccharomycetaceae、Debaryomycetaceae、Trichosporonaceae、Rhabditida 和 Trichostomatia 的共同存在。在肿胀和活跃分解期（87-209 ADD/3-7 天；TBS 为 11-20），双翅目是最丰富的真核生物类群。在高级分解阶段（267-448 ADD/9-15 天；TBS 为 21-25），Rhabditida 是最占优势的真核生物。干/骨骼遗体（734-1703 ADD/26-61 天；TBS≥26）以真菌科 Dipodascaceae、Debaryomycetaceae、Trichosporonaceae 和 Sporidiobolaceae 为主。使用整个研究的真核生物分类群的家族水平数据，随机森林模型解释了 ADD/天数变化的 89.58%，根均方误差（RMSE）为 177.55 ADD（约 6 天）。总的来说，这些结果强调了微生物真核生物群落在分解过程和估计 PMI 中的重要性。
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