Phosphate's abiotic stress and bioavailability limit its availability to plants. Plants collaborate with phosphorus solubilizing microorganisms to resolve this issue, resulting in a distinct microbial ecology. Bacterial diversity and other functional attributes of plant-associated microbial ecology in the endemic legume Humboldtia brunonis Wall. have been studied using 16s metagenomic amplicon analysis and culture-dependent selective media-based culture techniques. This study aimed to gain insight into bacterial diversity and isolate phosphate solubilizing bacteria. Bacterial isolates were grown in Pikovskaya's medium and incubated at a required temperature for 48 h before getting characterized by examining colony morphology with physiological and biochemical properties. The pure culture of bacterium is identified and assigned to its taxonomy using 16S rRNA gene sequence analysis as a tool. Brevibacillus brevis is the phosphate solubilizing endophyte associated with this endemic plant. A clear zone encircling the bacterial colony on Pikovskaya's medium indicates that this bacterium can solubilize phosphate. To better apprehend the endophytic root bacterial diversity, Illumina MiSeq metagenomics using the GAIA workflow, discovered forty-three endophytic bacterial species. The use of METAGENassist and KEGG database examined taxonomic and functional attributes of the endophytes. Exploration of biofertilizing, biocontrolling, and phytostimulating abilities is evident by the presence of the bacteria contributing to dinitrogen and nitrogen fixers, carbon fixers, ammonia oxidizers, and nitrite reducers. The figure also emphasizes their energy sources, oxygen requirement, sporulation, and their nature of interaction with the plant. The endophyte community also delivers information on this endemic plant's survival strategy.

Legumes are cosmopolitan plants, and nodulating legumes are well known for their symbiotic nitrogen-fixing ability by rhizobia-legume interaction. Biological nitrogen fixation in non-nodulating endemic legumes by associative or endophytic symbiotic bacteria requires much needed attention. Three non-nodulating legumes, namely, Humboldtia brunonis Wall., Kunstleria keralensis C.N. Mohanan and N.C. Nair, and Bauhinia phoenicea Wight and Arn., endemic to the Western Ghats regions of Karnataka state, were studied. Employed techniques of selective culture media to understand diazotrophic diversity inside the roots of these plants. The isolates that can grow in a nitrogenfree semisolid agar medium have been considered positive for nitrogen-fixing ability. nifH gene is taken as the marker gene to ascertain the nitrogen-fixing ability of the bacteria. The qualified bacterium in the previous steps is identified using 16s RNA sequencing and the Sanger sequence method. The results obtained showed B. phoenicea Wight and Arn. and H. brunonis Wall. as Caulobacter segnis, and in K. keralensis C.N. Mohanan & N.C. Nair, it is Caulobacter crescentus. The presence of the nifH gene is demonstrated through molecular methods. This work adds to the diverse works of Caulobacter as a successful plant growth-promoting endophyte even in the nitrogen-deficient, slopy soils of the Western Ghats.