Salivary microbiome signatures of Poles and Serbians and its potential for prediction of biogeographic ancestry

Biogeographical ancestry analysis is valuable in forensic investigations, especially in missing person cases or crimes without eyewitnesses, as it helps to infer geographic origins from genetic markers. This approach enhances forensic efforts by providing essential clues for identifying individuals with limited direct evidence. Slavic-speaking populations are poorly distinguishable based on human genome variability. However, recent studies show that even populations with close biogeographic origin could be differentiated based on salivary microbiomes. Nevertheless, the salivary microbiomes of Slavs have not been characterized yet. Therefore, this study aimed to compare the composition of the salivary microbiomes of Western and Southern Slavs’ representatives. 16S rRNA libraries from salivary microbiomes of 40 Poles (Western Slavs) and 40 Serbians (Southern Slavs) were prepared via PCR and sequenced on the MiSeq FGx platform (Illumina), giving approximately 100,000 reads per sample. Bioinformatic and statistical analyses were performed to assess the alpha and beta diversity of microbiomes and determine the differences in the abundance of bacterial genera between the groups studied. Analyses of alpha (ACE, Chao1, Shannon, and Simpson) and beta (Jaccard and Bray-Curtis dissimilarity) diversities in the salivary microbiomes clearly distinguished between Poles and Serbians. Alpha and beta diversity metrics were significantly higher in the Serbian population. Fusobacterium, Lautropia, Porphyromonas, Actinobacillus, Capnocytophaga, and Kingella were the most significantly increased genera in Serbians, whereas Veillonella, Selenomonas, Megasphaera, and Atopobium were more prevalent in Poles. In summary, our study identified significant differences in the salivary microbiomes of Poles and Serbians, with distinct microbial signatures associated with each population. These findings highlight the potential of salivary microbiome analysis as a tool for predicting biogeographic ancestry. Nevertheless, further analysis extended to other Slavic-speaking populations is necessary to clarify this issue.