Comparative Evaluation of the Salivary and Buccal Mucosal Microbiota by 16S rRNA Sequencing for Forensic Investigations

Abstract

The human microbiome has emerged as a new potential biomarker for forensic investigations with the development of high-throughput sequencing and bioinformatic analysis during the last decade. The oral cavity has many different microbial habitats, with each habit colonized by specific and individualized microbiota. As saliva and buccal mucosa are common biological evidence in forensic science, understanding the differences of microbial communities between the two is important for forensic original identification. Moreover, the oral microbiota is individualized, whereas there are few studies on the application of forensic personal identification that need to be supplemented. In this study, Streptococcus was the most abundant genus, with an average relative abundance of 49.61% in the buccal mucosa, while in the saliva, Streptococcus, Veillonella, and Neisseria had similar proportions (20%, 15%, 16%) and were the dominant genera. The α and β diversity displayed a significant distinctness between the saliva and buccal mucosal groups. The community assembly mechanism stated that the deterministic process played a more significant effect in shaping the salivary bacterial community assembly than buccal mucosa, which explained the microbial differences. Of the test samples, 93.3% can be correctly classified with the random forest model based on the microbial differences. Targeting the low-abundance bacteria at the species level, 52% of experimental participants could be discriminated by using the observed unique bacterial species. In conclusion, the salivary bacterial community composition differed from that of the buccal mucosa and showed high richness and diversity. With the random forest model, the microbiota of saliva and buccal mucosa can be classified, which can be used in identifying the source of oral biological trace. Furthermore, each individual has a unique bacterial community pattern, and the presence or absence of unique bacteria and differences in the composition of the core oral microbiota are the key points for forensic personal discrimination that supplement the study of oral microbial application to forensic personal discrimination. Whether for original identification or personal discrimination, the oral microbiome has great potential for application.

Oral Microbiota Signatures in the Pathogenesis of Euthyroid Hashimoto’s Thyroiditis

“…The prepared library was measured with a Qubit fluorometer and sequenced after normalization. Sequencing was performed on the MiSeq instrument (Illumina, San Diego, CA, USA) following the paired-end 2 × 300 bp protocol according to the manufacturer’s recommendations [ 24 ].…”

Pseudomonadota in the oral cavity: a glimpse into the environment-human nexus

“…The facts that members of these genera can thrive in soil, water, and plants, where human and animal excreta can be also present, and have typically highly dynamic genomes, suggest that these bacteria can serve as vectors of clinically relevant features (e.g. antibiotic resistance, virulence) from the environment to humans (Sanz-García et al 2021 ; Wang et al 2022a , 2022b ). Indeed, the summary provided in Table 1 shows that bacteria of some of these genera hold a broad set of antibiotic resistance genes, generically included in the categories efflux, inactivation, target modification, reduced permeability, among others, that are shared by other Pseudomonadota .…”

“…The broad diversity of oral microbiomes was evidenced by Tierney et al (2019) who, based on the analysis of 1473 oral metagenomes, identified 23 961 508 genes, half of which were unique in each metagenome. Such a uniqueness has led some authors to propose the oral microbiome profile as a valuable tool for biogeography investigations or forensic personal discrimination (Wang et al 2022a(Wang et al , 2022b.…”

“…Accordingly, the human microbiome is affected by the surrounding environment, with the geography, diet, and lifestyle shaping its structure (Cunningham et al 2017;Osterhaus et al 2020). In particular, the oral microbiome is expected to be influenced by external conditions that include not only the range of microorganisms to which humans are exposed, for instance, via food products, but also by lifestyle and hygiene habits (Freire et al 2020;Peters et al 2018;Tang et al 2019;Wang et al 2022aWang et al , 2022b.…”

“…Acinetobacter , Pseudomonas , Enterobacteriaceae ) (Ferro et al 2019 ; Jordi Rello et al 2019 ; Vaz-Moreira et al 2014 ; Rizzatti et al 2017 ; Theuretzbacher et al 2020 ). Curiously, in spite of these clinically relevant features and although Pseudomonadota are the second most abundant phylum in the mouth (Wang et al 2022b ), not much attention has been given to its presence. Indeed, in discussions about the oral microbiome and its relevance, Pseudomonadota are frequently underexplored when compared with other groups (Radaic and Kapila 2021 ; Zhang et al 2018 ).…”