Occurrence of Phosphate-Solubilizing Bacteria inRhizospheric and Pneumatophoric Sediment ofAvicennia marina

The present study deals with the isolation and characterization of phosphorus-solubilizing bacteria (PSB) from Avicennia marina rhizospheric sediment, pneumatophoric sediment and non-rhizospheric sediment. The sampling was carried out in four mangrove forests of Mumbai, India. The physicochemical parameters like pH, electrical conductivity, organic carbon, texture, total Phosphorus (P), inorganic P, organic P, Olsen P, iron, calcium, magnesium and zinc in sediment were analysed along with the isolation and molecular characterization of PSB. Significantly, lower pH was observed in the rhizospheric sediment than in the pneumatophoric and bulk sediment. Abundance of PSB was also found in the rhizospheric zone. This was supported by other physicochemical parameters such as high organic P, Olsen P, and higher bacterial count along with low inorganic P. In this study, 8 PSB were isolated and 16S rDNA sequence revealed that all the isolates belong to the genus Bacillus. Among the PSB isolates, B. subtilis sub. spizizenii TU-B-10 showed significantly higher solubilization activity (85.8±0.0 µg P released per 108 cfu in 72 hrs). The isolates that showed higher phosphate-solubilizing potentials can be explored as phosphatic bio-fertilizer to enhance the agricultural, aquacultural and mangrove productivity.