Isolation of Inorganic-Phosphate-Solubilizing Bacteria and Analysis of their Effect on Phosphorus Release from Lagoon Sediments

Internal phosphorus (P) loading from sediments is an important cause of eutrophication, and inorganic-phosphate-solubilizing bacteria (IPB) are known to play a vital role in the process of sediment P release. In this study, 10 IPB strains were isolated from the sediments of a lagoon suffering from macroalgal blooms dominated by Chaetomorpha linum - Rongcheng Swan Lagoon, China - and their taxonomy was determined by 16S rRNA sequence analysis. The phosphate-solubilizing characteristics of the obtained IPB strains were evaluated using a liquid medium, and the ability of IPB strains to dissolve P from sediments and the transformation of inorganic phosphorus (IP) fractions were investigated by inoculating IPB strains into a sediment-water experimental system. The 10 isolated IPB strains belonged to one family, two genera, and four species. All IPB strains in the liquid medium culture dissolved tricalcium phosphate, but the phosphate-solubilizing ability of IPB varied greatly between strains and appeared to be promoted when the strains were grown in mixed-strain cultures. Bacillus megaterium showed the strongest phosphate-solubilizing ability. The IPB inoculation experiment showed a large decrease in the Ca-bound P (HCl-P) concentration of sediments in various IPB inoculation treatments, especially in sediments from the central lake. Our results indicate that, under the action of IPB, there is great potential for the release of HCl-P, which is the primary IP fraction of lagoon sediments, and more attention should be given to the endogenous P pollution in Swan Lagoon Wetland.