Variations in oral microbiome and its predictive functions between tumorous and healthy individuals

Introduction. The oral cavity is one of the largest reservoirs of microorganisms and many pathogenic bacteria have been shown to be associated with the aetiology of oral cancers. Gap Statement. Owing to the complexity of oral microbial communities and their unclear relationship with oral cancer, identi-fication of specific bacteria which contribute to oral cancer is a key imperative. Aim. To compare and investigate the variations in the composition of the bacterial microbiome and its functions between patients with oral tumorous lesions and healthy subjects. Methodology. Twenty -seven samples from individuals with oral tumours (five oral benign tumours and 22 oral squamous cell carcinomas) and 15 samples from healthy subjects were collected. Genomic DNA was extracted and the V3-V5 region of the 16S rRNA gene was sequenced. Subsequently, bioinformatic assessment was conducted using QIIME2, PICRUSt and linear discriminant analysis effect size analyses (LEfSe). Results. The oral microbiota was composed mainly of the phyla Proteobacteria (31.76%, 35.00%), Bacteroidetes (30.13%, 25.13%) and Firmicutes (23.92 %, 17.07 %) in tumorous and healthy individuals, respectively. Neisseria, Prevotella, Fusobacterium, Streptococcus, Capnocytophaga, Veillonella, Haemophilus, Prevotella, Porphyromonas and Leptotrichia were the most abundant genera. Alpha diversity in the tumour group was significantly greater than that in the healthy group (P<0.05). Differential analy-sis of microbes between groups demonstrated a significantly higher number of Neisseria, Veillonella, Streptococcus, Leptotri-chia, Lautropia, Sphingopyxis, Sphingobium, Tannerella, Actinomyces and Rothia in healthy controls compared with the tumour group. However, the genera Treponema, Micrococcus, Pseudomonas, Janthinobacterium, Parvimos, Loktanella, Staphylococcus, Acinetobacter, Catonella, Aggregatibacter and Propionibacterium were significantly higher in the tumour group. Pathways related to cancers, cell motility, environmental adaptation, metabolism and signal transduction were enhanced in the tumour group, while functions associated with immune system diseases, replication, repair and translation were significantly enhanced in the healthy group. Conclusion. Variations in the oral microbiota and its functions showed a correlation with oral tumours. The tumour group showed an increased abundance of some multi- drug-resistant and periodontitis-related pathogens. The significantly altered microbiotas may serve as potential biomarkers or inform combination therapy for oral tumours.