Characterization of phosphobacteria isolated from eutrophic aquatic ecosystems.

Phosphobacteria are able to enhance phosphorus availability in soil and improve crop yields. To develop such biofertilizers, 14 predominant phosphobacteria were isolated from eutrophic aquatic ecosystems. Molecular identification and phylogenetic analysis revealed three groups among the nine isolates of inorganic phosphate-solubilizing bacteria (IPSB): IPSB1 and IPSB2 belonged to the actinobacteria and flavobacteria, respectively, and the other seven belonged to the gamma-proteobacteria. Among five isolates of organic phosphorus-mineralizing bacteria (OPMB), two groups were present: OPMB1 and OPMB3 belonged to the beta-proteobacteria, while the other three belonged to the gamma-proteobacteria. The IPSB isolates released 62.8-66.7 mg P 1(-1) from tricalcium phosphate under shaking conditions, and 26.8 to 43.7 mg P 1(-1) under static conditions; the OPMB strains released 23.5-30.2 mg P 1(-1) from lecithin under shaking conditions, and 16.7-27.6 mg P 1(-1) under static conditions. To the best of our knowledge, this is the first report indicating that IPSBI (designated Aureobacterium resistents) as a tricalcium phosphate-solubilizing bacterium and OPMB1 and OPMB3 (designated Acidovorax temperans and Achromobacter xylosoxidans, respectively) are lecithin-mineralizing bacteria. This investigation demonstrated that a eutrophic aquatic ecosystem is a selective source of phosphobacteria and the screened phosphobacteria are a potential alternative to the development of biofertilizers.