Characterization of Plant Growth Promoting Rhizobacteria of Bacillus and Pseudomonas Species from Soil Isolates through DNA Sequencing

Abstract

Plant growth-promoting rhizobacteria (PGPR) play a crucial role in sustainable agriculture by enhancing plant growth, nutrient availability, and resistance to environmental stresses. The present study aimed to isolate, characterize, and molecularly identify Bacillus and Pseudomonas species from soil samples collected from the campus site of Doon (PG) Paramedical College, Dehradun, Uttarakhand. Isolation was performed using serial dilution and selective media techniques, followed by morphological and biochemical characterization. Three bacterial isolates (S1, S2, and S3) were obtained and screened for plant growth-promoting traits including phosphate solubilization, indole-3-acetic acid (IAA) production, and siderophore synthesis. Among the isolates, S2 (Pseudomonas sp.) exhibited the highest phosphate solubilization zone (16 mm), maximum IAA production (0.8387 OD at 72 h), and significant siderophore activity (1.5733 OD at 450 nm). Thin layer chromatography confirmed IAA production with Rf values ranging from 0.46 to 0.66. Plant inoculation studies using Hordeum vulgare (barley) and Solanum lycopersicum (tomato) demonstrated enhanced shoot growth in treated plants compared to controls, with Pseudomonas isolate showing superior performance. Molecular identification through 16S rRNA gene sequencing confirmed isolate S1 as Priestia aryabhattai (formerly Bacillus coagulans), belonging to the family Bacillaceae. The findings highlight the multifunctional plant growth-promoting potential of native Bacillus and Pseudomonas strains and support their application as eco-friendly biofertilizers and biocontrol agents for sustainable agricultural practices.