Ecological and genomic insights into seaweed-associated Verrucomicrobiota from the Gulf of Mannar

Members of the phylum Verrucomicrobiota are increasingly recognized for their ecological versatility and capacity to degrade complex polysaccharides across diverse marine and freshwater ecosystems. In this study, we recovered 11 metagenome-assembled genomes (MAGs) affiliated with the orders Puniceicoccales and Verrucomicrobiales from seaweed-associated microbiomes in the Gulf of Mannar, India. Verrucomicrobiota constituted 0.6%–2.9% of the total bacterial community across the analyzed algal samples, indicating their consistent presence but low abundance in these habitats. Five high-quality MAGs (JB022, JB024, JB025, JB027, JB023; completeness >90%, contamination <5%) were selected for detailed genomic and ecological characterization. Phylogenomic analyses revealed that these MAGs form distinct lineages within known Verrucomicrobiota families, expanding the known diversity of this phylum in marine algal ecosystems. Comparative genomic analysis showed that these genomes encode diverse biosynthetic gene clusters and a rich repertoire of carbohydrate-active enzymes (CAZymes) and sulfatases, suggesting adaptation to the degradation of polysaccharides typical of seaweed substrates. These binned genomes also possess genes related to fermentative metabolism, nitrogen fixation, and partial denitrification, indicating metabolic versatility and potential contributions to nutrient cycling within algal holobionts. These findings reveal that seaweed-associated Verrucomicrobiota from the Gulf of Mannar represent phylogenomically distinct and functionally specialized lineages with ecological relevance in carbon and nitrogen cycling in coastal marine ecosystems. This study provides the first genomic insights into seaweed-associated Verrucomicrobiota from India, representing potential new taxa and underscoring their potential roles in polysaccharide degradation and holobiont functioning. IMPORTANCE Coastal biomes harbor a rich diversity of microorganisms, and only a few studies have focused on the diversity and functional role of members of the phylum Verrucomicrobiota . Despite their low abundance, members of the phylum Verrucomicrobiota can play an important role in regulating the fate of carbon within marine ecosystems. This study presents the first identification of novel Verrucomicrobial taxa from India, particularly from the Gulf of Mannar, a marine biodiversity hotspot with limited prior microbial investigations. Through metagenome-resolved genomic analysis, this work infers the potential ecological role of these newly discovered Verrucomicrobiota members and suggests their probable role in the carbon cycling and ecosystem processes.