Stress-Tolerant Viridibacillus arenosi Strain IHB B 7171 from Tea Rhizosphere as a Potential Broad-Spectrum Microbial...

Viridibacillus arenosi strain IHB B 7171 identified based on 16S rRNA gene sequence produced colony forming units (cfu/ml) ranging from 3.3 × 10⁴ to 1.2 × 10¹⁰ under pH 5-11, 2.2 × 10² to 1.4 × 10¹⁰ for temperature 5-40 °C, 2.4 × 10² to 1.1 × 10¹⁰ for PEG 6000 10-30%, 2.2 × 10² to 1.4 × 10¹⁰ for 2.5-10% NaCl, 3.1 × 10³ to 1.7 × 10⁹ for 2.5-7.5 mM CaCl₂, 2.2 × 10² to 1.4 × 10⁷ for 2.5-7.5 mM AlCl₃, and 3.2 × 10² to 1.2 × 10⁷ for 2.5-7.5 mM FeCl₃. The activities of plant growth-promoting attributes with the increasing acidity, desiccation and salinity ranged from 408 to 101, 20 to 8, 14 to 5 µg/ml P-liberated from tri-calcium phosphate, aluminium phosphate and iron phosphate, 20-9% siderophore units, 14-4 µg/ml IAA and 190-16 α-ketobutyrate h/mg protein ACC-deaminase activity. Plant height, leaf number, and leaf weight on treatment with bacterial inoculum showed an increment of 9.5, 17.6, 54.5 and 31.0% in tea seedlings, respectively. The bacterium also enhanced plant height and yield by 10 and 13% in pea and 2.8 and 13.9% in wheat. The results exhibited stress-tolerance and plant growth-promoting activities by the strain under stressed growth-conditions with potential as a broad-spectrum plant growth-promoting rhizobacterium.