Isolation and Characterization of Organic Phosphorus-Mineralizing Bacteria in Sediment of a Chinese Large Shallow Eutrophic Lake (Lake Taihu)

Abstract

The organic phosphorus mineralizing bacteria (OPB) play an important role in phosphorus cycling in lake sediment, to which less attention has been paid. Monthly sediment samples in 2009 ending in October, together with the samples from different seasons (May, July, October, and December) in 2008, were collected at 6 sites in a Chinese large shallow eutrophic lake (Lake Taihu). The sediment OPB numbers ranged from 2.2 × 106 to 1.79 × 108 cells g−1 (dry weight) at different sampling sites and in different seasons, with the average being 3.88 × 107 cells g−1 (dry weight). Its number was highest at the most polluted site and peaked in spring and summer, which can be explained by the enrichment of organic matter in sediment. Furthermore, there existed a significant positive relationship between the OPB numbers and alkaline phosphatase activities in the sediment. The 6 OPB strains isolated from the sediment were distinct in terms of their colony morphology on the yolk agar, biochemical characteristics and phosphorus release abilities. According to the 16S rDNA sequences, these OPB belong to Bacillus cereus, Stenotrophomonas maltophilia, Stenotrophomonas sp., Bacillus cereus, Xanthomonas sp., Pseudomonas sp. They were distinguished from the OPB species recorded in a Chinese small shallow eutrophic lake whose sediment organic content was remarkably higher. Taken together, organic matter shaped the OPB community not only quantitatively but also qualitatively, which in concert facilitated the enzymatic hydrolysis of organic phosphorus in lake sediment.