Mei Shuyan, Zhao Ming, Liu Yanfang, Zhao Congying, Xu Hui, Fang Yating, Zhu Bofeng
Multi-Omics Innovative Research Center of Forensic Identification; Department of Forensic Genetics, School of Forensic Medicine, Southern Medical University, Guangzhou 510515, P. R. China.
School of Nursing, Guangdong Medical University, Dongguan 523808, P. R. China.
Forensic Sci Int. 2022 Feb;331:111128. doi: 10.1016/j.forsciint.2021.111128. Epub 2021 Nov 29.
Body fluids are one of the common biological traces at crime scenes. Understanding the types of these biological traces could provide key clues for the investigations of the forensic cases. In recent years, partial hypervariable regions of 16S rRNA gene sequencing and full-length 16S rRNA gene sequencing have attracted the interests of researchers and we intend to explore which method can be better applied to forensic researches.
In this study, the 16S rRNA gene V3-V4 (short-read) sequencing based on next-generation sequencing and the full-length 16S rRNA gene sequencing based on single molecule real-time sequencing were used to classify microbes in saliva, peripheral blood, vaginal secretion and menstrual blood samples.
Alpha diversity metrics in short-read sequencing were larger than those of full-length sequencing. Phylum-level bacteria in four kinds of body fluids obtained from the two platforms were similar, while their abundances were different. The results of principal coordinates analysis and analysis of molecular variance indicated the microbial compositions of vaginal secretion and menstrual blood samples were similar, and the microbial compositions among saliva, peripheral blood, vaginal secretion or menstrual blood samples were significantly different. The linear discriminant analysis effect size showed the differential bacteria screened among the four kinds of body fluids were variant in two sequencing results.
Both sequencing methods could be used to detect bacterial diversities in four different types of body fluids and provide potential tools for microbes to identify the four kinds of body fluids in forensic investigation, in which full-length sequencing could provide more accurate taxonomy.
体液是犯罪现场常见的生物痕迹之一。了解这些生物痕迹的类型可为法医案件调查提供关键线索。近年来，16S rRNA基因测序的部分高变区和全长16S rRNA基因测序引起了研究人员的兴趣，我们打算探索哪种方法能更好地应用于法医研究。
在本研究中，基于新一代测序的16S rRNA基因V3-V4（短读长）测序和基于单分子实时测序的全长16S rRNA基因测序被用于对唾液、外周血、阴道分泌物和月经血样本中的微生物进行分类。
短读长测序中的α多样性指标大于全长测序。从两个平台获得的四种体液中的门水平细菌相似，但其丰度不同。主坐标分析和分子方差分析结果表明，阴道分泌物和月经血样本的微生物组成相似，而唾液、外周血、阴道分泌物或月经血样本之间的微生物组成存在显著差异。线性判别分析效应大小显示，在两种测序结果中，四种体液中筛选出的差异细菌有所不同。
两种测序方法均可用于检测四种不同类型体液中的细菌多样性，并为法医调查中通过微生物鉴定这四种体液提供潜在工具，其中全长测序可提供更准确的分类学信息。
