The salivary microbiome for differentiating individuals: proof of principle

Abstract

Human identification has played a prominent role in forensic science for the past two decades. Identification based on unique genetic traits is driving the field. However, this may have limitations, for instance, for twins. Moreover, high-throughput sequencing techniques are now available and may provide a high amount of data likely useful in forensic science.This study investigates the potential for bacteria found in the salivary microbiome to be used to differentiate individuals. Two different targets (16S rRNA and rpoB) were chosen to maximise coverage of the salivary microbiome and when combined, they increase the power of differentiation (identification). Paired-end Illumina high-throughput sequencing was used to analyse the bacterial composition of saliva from two different people at four different time points (t ¼ 0 and t ¼ 28 days and then one year later at t ¼ 0 and t ¼ 28 days). Five major phyla dominate the samples: Firmicutes, Proteobacteria, Actinobacteria, Bacteroidetes and Fusobacteria. Streptococcus, a Firmicutes, is one of the most abundant aerobic genera found in saliva and targeting Streptococcus rpoB has enabled a deeper characterisation of the different streptococci species, which cannot be differentiated using 16S rRNA alone. We have observed that samples from the same person group together regardless of time of sampling. The results indicate that it is possible to distinguish two people using the bacterial microbiota present in their saliva.

Does interindividual variability of saliva affect the release and metabolization of aroma compounds ex vivo? The particular case of elderly suffering or not from hyposalivation

“…However, most of the studies on this topic have employed pooled salivas or individual salivas from a limited number of subjects (Buettner, 2002a(Buettner, , 2002bGenovese et al, 2009;Munoz-Gonzalez et al, 2018b;Munoz-Gonzalez et al, 2014;Pages-Helary et al, 2014) that do not represent properly the well-known interindividual variability of human saliva composition in healthy individuals (Leake, Pagni, Falquet, Taroni, & Greub, 2016;Neyraud, Palicki, Schwartz, Nicklaus, & Feron, 2012). Additionally, different pathologies or functional states can provoke biochemical and microbiological changes in salivary parameters raising the differences in specific populations (Castagnola, Cabras, Vitali, Sanna, & Messana, 2011;Schipper, Silletti, & Vinyerhoeds, 2007).…”

Circadian oscillations of microbial and functional composition in the human salivary microbiome

“…The salivary microbiomes can be characterized by a significantly lower interindividual variability than microbial communities of other body sites such as the gut, 7 , 8 but it is possible to differentiate individuals by phylogenic approaches 9 . Though the salivary microbiome is associated with gut microbiome, 10 , 11 the diversity in salivary microbiomes showed relatively low associations with several affecting factors including long-term diet, 12 weight and gender, 13 geographic location, 14 and antibiotic treatment (high tolerance) 15 compared with that of the gut microbiome.…”

Integrating the microbiome as a resource in the forensics toolkit

“…Researches have demonstrated the potential to identify a single individual in large populations, based on microbial fingerprints from metagenomic tags, even over long periods of time [42,55]. It has also been shown that skin bacterial profiles can be confidently used to link specific individuals to objects touched, even after months [56], provided the objects have since remained untouched [31].…”