Dynamics and diversity of phosphate mineralizing bacteria in the coral reefs of Gulf of Mannar

Phosphatase Producing Bacteria (PPB) and Inorganic Phosphate Solubilizing Bacteria (IPSB) are important to reef nutrition. These microbes and phosphate concentration play a significant role in the productivity of coral reef ecosystems. A study was conducted in Gulf of Mannar coral reef ecosystem to understand the diversity of these groups of bacteria and their competence in mineralizing the phosphate. The PPB isolates were identified under six genera i.e. Bacillus, Pseudomonas, Micrococcus, Vibrio, Arthrobacter and Brevibacterium. Likewise, the IPSB isolates were also identified that belong to six genera i.e. Bacillus, Arthrobacter, Pseudomonas, Flavobacterium, Flavomonas and Micrococcus. Among the PPB and IPSB strains, Bacillus represented more number of species than others. PPB exhibited maximum activity between pH 8 and 9 and the lowest was at pH 6. Among the phosphatase producers Bacillus cereus (546) showed maximum activity (0.333 mmol/l P) at pH 8. In general, the phosphatase activity in most of the Bacillus species varied with reference to different pH. The species Bacillus megaterium (573) showed highest phosphate solubilizing activity (0.906 mmol/l P) by producing 2-ketogluconic acid. The production of organic acids and phosphatase enzymes by these bacterial groups are responsible for the conversion of insoluble inorganic and organic phosphates into soluble forms which are available for the reef organisms.