Unravelling the complex bacterial diversity in the rice rhizosphere of Kole lands of Thrissur through the metagenomics approach.

The Kole wetlands of Kerala are highly productive rice ecosystems that lie below mean sea level and alternate between flooded and dry phases, shaping their ecological structure. This study focused on assessing bacterial diversity in the rice rhizosphere of Thrissur Kole lands. Rhizosphere soil was sampled from three Kole wetland locations, Puzhakkal (Pzk), Mullassery (Mls), and Cherpu (Chr). Bacterial communities were profiled by constructing metagenomic libraries and sequencing the 16S rRNA V3-V4 regions using the Illumina MiSeq platform. The sequences of the samples Pzk, Mls, and Chr were submitted in the SRA portal under the bioaccession numbers SAMN17776076, SAMN17776077, and SAMN17776078, respectively. High-quality, chimera-free sequences were clustered into OTUs using the QIIME pipeline. Taxonomic assignment was performed in MEGAN by matching reads to sequence databases and allocating NCBI-based taxon IDs. Phylum-level bacterial and archaeal diversity was further analyzed using the MG-RAST pipeline. The predominant bacterial phyla identified were Proteobacteria, Chloroflexi, Acidobacteria, Actinobacteria, Bacteroidetes, and Nitrospirae, with bacterial relative abundance being highest in the Pzk sample and comparatively lower in the Chr sample. The major archaeal phyla included Euryarchaeota, Crenarchaeota, and Thaumarchaeota. Many members of these bacterial and archaeal groups are known to thrive in waterlogged, oxygen-limited, or anoxic conditions, characteristic of Kole lands. Plant Growth Promoting Rhizobacteria (PGPR) such as Azospirillum, Paenibacillus, and Cellulosimicrobium were detected and could potentially be exploited as acid-tolerant biofertilizers. Biocontrol agents belonging to the genera Bacillus and Pseudomonas were also present. Further investigation is required for the characterization of the 'Unclassified' genera at taxonomic and functional levels to elucidate their ecological functions. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-025-04630-w.