微生物对于尸体的腐解和昆虫演替的影响及其对于死亡时间推断的价值研究

The feasibility of the determination of the postmortem interval of human remains based on insects has been demonstrated through research and actual forensic investigations. But the integration of entomological evidence as an essential part of an investigation still remains has not occurred. Furthermore, research is still needed to ensure that it meets the Daubert criteria. A primary concern is estimating the amount of time to elapse from death until colonization of human remains by insects. Consequently, we must continue conducting such research in order to increase our accuracy with determining when colonization occurs and potential death of the individual in question. While insects are easily observed on a corpse and they are known to be primarily responsible for the decomposition process, microbes on the remains are essential for the process to occur. They release volatiles that attract the insects to the remains. And, in many instances, these volatiles (i.e., semiochemicals) dictate insect succession patterns on the remains. To what extent do microbes impact insect invasion and subsequent succession is not known. If insect invasion time and duration on a corpse is mediated by volatiles produced by the microbes is not known. Can the microbe succession on a corpse and associated volatile dynamic be quantified and used to estimate the PMI of a corpse? In this project we will carry out research to answer the aforementioned questions. Many new methods such as decomposition simulation, ECO BIOLOG and SPME-GC/MS will be employed. Our research will provide scientific basis and application database for the determination of PMI based on insects, microbes and volatiles.

昆虫用于死亡时间（PMI）推断的可行性已被理论和案例所证明，由于一些不确定性特别是昆虫入侵尸体时间的变异的存在使得昆虫学仍被排除在法医学调查的基本检查之外。从更深的机理来揭示昆虫在尸体上的演替规律以提高死亡时间推断精确度是必走之路。尸体腐解的原因是昆虫和微生物的作用，其中昆虫起主要作用且容易被观察，研究表明微生物分解尸体产生的挥发物是各类昆虫籍以远距离搜寻并入侵尸体的信号，在昆虫和微生物之间存在互动。微生物如何准确的影响各类昆虫的入侵和及随后的演替？在温湿度确定的情况下，环境的微生物本底是否决定了昆虫入侵尸体的时间及尸体达到白骨化所需时间？尸体上的微生物群落、腐解产生的挥发物是否可以量化用于推断死亡时间？本项目拟采用尸体腐解模拟、微生物ECO BIOLOG检测、SPME-GC/MS分析等方法对以上问题进行研究，从而为根据昆虫、微生物及挥发物判断死者的PMI提供理论依据和应用数据基础。

死亡时间推断是法医学的百年难题,死后尸体形态及化学变化的mosaic特征使得常规法医学方法无法用于腐败尸体的死亡时间推断。昆虫和微生物是死后尸体上存在的两大类活着且处于变化的生物,它们共同作用加上尸体的自溶促使尸体变成白骨。本项目在广州、深圳及苏州市利用人类与动物尸体在野外及试验室对此两类生物进行了研究。结果显示微生物变化同样能够用于死亡时间推断，微生物和昆虫之间存在利用及竞争。在隔离昆虫的情况下，尸体最终会木乃伊化。尸体上的微生物，除了尸体自身之外，昆虫也携带了较多外源微生物。微生物代谢功能多样性与蛆虫数量变化呈负相关关系。Biolog-Eco 法能表现死亡后0~240 h 尸体上微生物群落对部分碳源利用的代谢差异，有望为死亡时间推断提供新依据。在尸体腐败不同阶段出现的昆虫精确的发育规律能够提供符合duobert法则的精确的最短死亡时间（PMImin）。本项目在国际上第一次针对甲虫筛选出判断死亡时间的精确指标。对于腐败微生物的变化需要采用新一代测序的方法进行更深的基础研究。本项目研究为国际死亡时间推断及法医昆虫学领域提供了重要的基础数据。通过本项目研究已经发表SCI收录期刊论文8篇，国内期刊论文7篇，国际合作出版专著一本，在国际会议上做报告2次，其余成果尚处于整理之中，在一线公安70多起案件中利用本技术提供死亡时间推断。