Transcription and microbial profiling of body fluids using a massively parallel sequencing approach

Analysis of biological evidence typically begins with a preliminary screening for the presence of biological fluids, traditionally with enzymatic or immunologic tests and of late by RNA profiling. The goal of this study was to create a whole transcriptome protocol, to view potential degradation effects in forensically relevant body fluids. Total RNA from fresh and aged blood, menstrual blood, saliva, semen, skin and vaginal secretion was analyzed with a massively parallel sequencing method. Two RNA-Seq library protocols with and without rRNA depletion were tested and compared. The rRNA depletion step had a negative influence on the sequencing quality and on the downstream analyses. From the human and bacterial RNA sequences, source-specific signatures could be identified. Aged samples showed in general a higher level of RNA degradation and decreased bacterial diversity. In summary, we could show that transcriptional profiling and metagenome analysis are powerful tools to provide additional information about the trace evidence.