Application Of Microbial Community In Five Types Of Human Biological Samples For Body Fluid And Tissue Traceability

BackgroundThe source identification of forensic biological materials play an important role in revealing the nature and process of criminal cases,but lack effective identification method at present.Different body fluid and tissue has different microbial composition,and human microbiome shows a good potential in body fluid and tissue identification.At present,most research in the field of forensic medicine focuses on the information mining of HMP database,which covers a limited population and sample size.The application and integration of the database are limited,which could not meet the actual needs of microbiome research.In addition,forensic material is usually affected by the external environment,and the microbiome is also affected by individual regional differences,but there is little research on this.In this study,16S rDNA high-throughput sequencing was used to detect microbial community of saliva,vaginal fluids,semen,skin and feces from healthy China Han population.The structures and abundances of the sample microflora will be analyzed through the bioinformatics methods,and on this basis,the microbial markers with significant differences will be screened.In addition,a random forest classifier based on microbial markers will be explored to establish a body fluids and tissues identification inference algorithm.Considering that the forensic material is actually affected by the external environment.In this study,the effects of environmental exposure on semen microbial community and different geographical factors on vaginal microbial community were preliminarily explored.And the application of microbiome in tracing the origin of mixed samples of body fluids and tissues was also studied.The aim is to identify the important factors that affect the application of human microbiome in body fluids and tissues identification,so as to provide new insight and strategy on the source identification.MethodIn this study,five kinds of common body fluids and tissues were collected according to a certain sampling standards.Meanwhile,semen samples exposed to different environments and the mixed samples of saliva deposited on facial skin were prepared.The 16S rDNA high-throughput sequencing was used to study five kinds of samples,and the microbial data sets of different body fluids were obtained.MetaStats,LefSe,etc.were used to analyze the differences of microbial community,and the linear discriminant analysis and Cladogram were plotted to observe the dominant microbes with significant differences among the groups.Then,the microbial markers used to body fluids and tissues identification were screened.Based on the data set obtained in this study,which contains information of microbial community of different body fluids and tissues,a random forest prediction model was established.ResultThere are significant differences in microbial community composition and dominant flora among five different types of body fluids and tissues,and the random forest model shows a high predictive ability for their correct classification.The dominant bacteria in saliva samples were Streptococcus and Neisseria;the dominant bacteria in vaginal secretion were lactic acid bacteria and Gardnerella;the dominant bacteria in skin were Propionibacterium and Corynebacterium;the dominant bacteria in semen were Pseudomonas and Escherichia-Shigella;the dominant bacteria in feces were Megamonas and Bacteroides.Although the microbial community of semen exposure group was affected by the environment,it could be distinguished from the other four body fluids.Biogeographical factors could affect the relative abundance of some vaginal flora,but there is no significant difference in the composition of vaginal dominant flora,mainly Lactobacillus and Gardnerella.Additionally,the microbial community in the mixed model of the facial skin area contaminated with saliva from the same and different individuals was clearly determined by the constituent fluids or tissue.Conclusion:Human microbiome shows a good application potential as a tool for five common body fluids or tissues identification in forensic medicine,and it has a good stability as the biomarkers.It will expected to be used for source identification of biological samples,providing vital evidence in determining the nature of crime scenes and safeguarding the justice of the law.