16S rRNA gene amplicon sequencing reveals lifestyle-associated gut microbiome variation among tribal, rural, and urban populations from North Arcot regions of Tamil Nadu, India

The gut microbiota in humans not only supports metabolism and immune function but also influences susceptibility to various diseases. Changes in lifestyle, diet, and environment are the major factors affecting the variety and capability of gut microbes. Despite the growing interest in microbiome research, there are still only a few comparative studies of the microbiomes of tribal, rural, and urban Indian populations, especially in terms of their potential pharmacological and therapeutic benefits. The present work was focused on investigating the gut microbiota profile, diversity, and inferred functional capabilities of three different populations of Tamil Nadu, India, tribal (Mulluvadi), rural (Odugathur), and urban (Vellore)with the aim of discovering microbiota features that could have pharmacological significance. Fecal samples ( n = 75; Mulluvadi tribal n = 25, Vellore urban n = 25, Odugathur rural n = 25; age 20–60 years) were analysed using 16S rRNA gene sequencing (V3-V4 region, Illumina MiSeq). Sequence data were processed using QIIME2 and DADA2, and taxonomic classification was performed against the SILVA 138 database. Microbial diversity was assessed using Chao1, Shannon, Simpson, and Fisher indices, while beta diversity was evaluated using BrayCurtis dissimilarity and principal coordinate analysis (PCoA). Functional profiles of microbial communities were predicted using PICRUSt2 and mapped to KEGG metabolic pathways. We found distinct microbial diversity patterns to characterize the three populations. Differences in microbial diversity were observed among the three populations, with variations in both species-richness and community evenness. Across groups, major phyla were Firmicutes, Bacteroidota, Actinobacteria, and Proteobacteria. In this study, the tribal microbiome showed characteristics consistent with fiber degradation and potential short-chain fatty acid production, likely associated with Prevotella / Segatella -dominated taxa. Functional prediction of the microbiomes of the three groups suggests an abundance of carbohydrate and amino acid metabolic pathways in the tribal microbiome, and membrane transport and xenobiotic metabolism pathways predominate urban microbiome. In summary, our study has revealed a lifestyle impact on gut microbial composition and metabolic potential differences among tribal, rural and urban populations of Tamil Nadu. The tribal microbiome showed enrichment of fiber-associated genera with predicted SCFA-related metabolic pathways. These findings are exploratory and require validation through individual-level sampling and functional analyses.