Experimental studies on isolation and characterization of silicate solubilizing Bacillus tequilensis SKSSB09

Abstract

Silica is a beneficial mineral that regulates the growth of plants and improves crop yields. Silica is a key factor in inducing the drought mitigation property and systemic acquired resistance in plants. Screening of silicate solubilizing bacteria on conventional medium forms white colonies on off-white media with translucent zones which makes the observation challenging. The present study used a modified plate assay by incorporating 0.0025% bromocresol purple in the Bunt and Rovira media which eases the screening process. The soil sample was collected from the maize rhizosphere, seven silicate solubilizing bacteria were isolated, among which SKSSB09 showed a better result. Bacillus tequilensis showed high silicate solubilization efficiency, that is, 546.23 ± 3.4 µg/mL with a silicate solubilization zone of 7.5 ± 0.6 mm. Gas chromatography–mass spectrometry analysis of the bacterial filter extracts detected the organic acids as propanoic acid, acetic acid, butanoic acid, and glycolic acid which are crucial factors in the dissolution of insoluble silicates. SKSSB09 also possess indole acetic acid production ability and the quantitative analysis showed 61.2 ± 3.6 µg/mL. SKSSB09 possess higher antagonistic activity which showed 99% of mycelial inhibition against Fusarium oxysporum. NCBI BLAST results of 16S rRNA gene sequence identified the SKSSB09 as B. tequilensis. This work highlights the importance of silicate solubilizing B. tequilensis SKSSB09 as a plant beneficial microbial inoculant.