Phosphate solubilizing epilithic and endolithic bacteria isolated from clastic sedimentary rocks, Murree lower Himalaya, Pakistan

Abstract

Rock microbes are capable to solubilize phosphate present in the rocks.. In this study, we focused on the isolation of phosphate solubilizing bacteria from rocks of Murree, Pakistan. Both endolithic and epilithic bacteria were screened for phosphate solubilization. Three bacterial strains were selected based on halozone formation inNational Botanical Research Institute for phosphate) medium supplemented with TCP (tribasic calcium phosphate). The solubilization index for these bacteria was recorded as 4.29, 4.03 and 3.99. The pH of the medium dropped from 7.0 to 4.0 after 5days with continuous shaking at 150rpm, which facilitate the phosphate solubilization. The strains P26, P4 and N27 were identified as Pseudomonas putida strain (KT004381), Pseudomonas grimontii (KT223621) and Alcaligenes faecalis (KT004385). Strain P26 showed maximum phosphate solubilization (367.54µg/ml), while P4 and N27 showed 321.88 and 291.36µg/ml after 3days of incubation. Such inorganic phosphate solubilization could be attributed to the organic acids production by bacteria. The presence of organic acids is determined by high-performance liquid chromatography. Three different types of acids, gluconic, oxalic and malic acid were the dominant acids found in the culture medium. It may be assumed that these bacteria can play a role in weathering of rocks as well. PSB is likely to serve as an efficient biofertilizer, especially in areas deficient in P to increase the overall performance of crops.