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Identification of unique microbial signatures pre- and post-coitus in male-female pairings by massively parallel sequencing and its potential to detect sexual contact

Dixon, Ruby (2022) Identification of unique microbial signatures pre- and post-coitus in male-female pairings by massively parallel sequencing and its potential to detect sexual contact. Honours thesis, Murdoch University.

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Abstract

Background: The capture of male DNA, post-assault, is important in sexual assault investigation, particularly where an offender is unknown to the victim. The recovery of DNA often occurs when the female victim undergoes a forensic medical assessment. Analysis regularly results in mixed autosomal DNA profiles. As these results contain both victim and perpetrator DNA, they are often difficult to interpret a searchable male profile. While STR profiling of the male Y-chromosome is often used to overcome this, the successful identification of an individual can be hindered by the paternal inheritance pattern of Y-STRs. An adjunct method of perpetrator identification lies with microbiome analysis using massively parallel sequencing.

Aims: This study aimed to identify ASVs that were unique to each participant and compare the bacterial communities found on the genitals pre- and post-coitus. From the sequence data derived, statistical analysis was performed to investigate if bacteria sequences could be used to infer contact between each male-female pairing.

Content: Samples were collected from 14 male-female pairings across two recruitment cohorts. Volunteers were asked to self-collect samples pre- and post-coitus. Samples were extracted using PureLink™ Microbiome DNA Purification Kit. Extracted DNA underwent library preparation using primers targeting the V1-V9 hypervariable regions of the bacterial 16S rRNA gene (~1,449 bp). Libraries were sequenced by PacBio® SMRT Sequel II sequencing platform. Unique bacterial signatures were detected in low frequencies (<1%) in male and female participants pre-coitus. The data indicates a disruption to microbial composition post-coitus. Further genomic analysis is needed to confirm species and subspecies classification of bacteria.

Item Type: Thesis (Honours)
Murdoch Affiliation(s): Medical, Molecular and Forensic Sciences
Supervisor(s): Chapman, Brendan and Egan, Siobhon
URI: http://researchrepository.murdoch.edu.au/id/eprint/66176
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