CHARACTERISTICS OF MICROCYSTIN-DEGRADING BACTERIUM ISOLATED FROM SEDIMENTATION PONDS FOR THE TREATMENT OF CYANOBACTERIAL BLOOMS

Cyanobacterial blooms occur worldwide due to eutrophication and climate changes, and microcystins (MCs) have been gainning increasing attention in recent years. A microcystin-degrading bacterium strain, named SW1, was isolated from sedimentation ponds for treating cyanobacterial blooms located at north rim of Lake Taihu. Based on 16S rDNA gene sequence phylogenetic analysis, SW1 was identified as Sphingopyxis sp. The optimal culture pH for SW1 was at 7, and it can also survived at pH 10. SW1 degraded MC-LR and MC-RR efficiently, and the degradation reactions followed first-order kinetics with reaction rate constants of 0.35/h and 0.28/h, respectively. The degradation ability of SW1 was significantly influenced by both temperature and pH. The degradation ability of SW1 was relatively high at 22℃-37℃, neutral pH and slight alkaline conditions. however, the degradation was strongly inhibited at low temperature ( 15℃) and extreme alkaline conditions. According to PCR analysis, mlrA homologous gene were found in both SW1 and samples from treatment ponds, suggesting that biodegradations were the possible pathway for MCs eliminations in these treatment ponds. Under proper environmental conditions, such as high water temperature and moderate pH, certain species of bacteria, SW1 for example, probably play a key role in rapid degradation of MCs.