蓝藻水华堆积处理池中微囊藻毒素降解细菌的分离及降解特性

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

微囊藻毒素(Microcystins,MCs)近年来由于蓝藻水华在世界范围内频发而受到广泛关注。从太湖北部蓝藻水华堆积处理池中分离出一株微囊藻毒素降解细菌SW1,经16S rDNA序列分析鉴定为鞘氨醇单胞菌(Sphingopyxis sp.)。SW1的生长最适pH为中性(pH 6—8),但也能生长于pH 10条件下。SW1对MCs的两种异构体MC-LR和MC-RR具有高降解活性,并表现出一级反应动力学特征,其降解速率常数分别为0.35/h和0.28/h。温度和pH对SW1降解活性有很强影响:在温度为22—37℃,pH中性或弱碱性条件下(MC-LR,pH6—9;MC-RR,pH 7—8),SW1具有高降解活性;而在低温和强碱性条件下其降解活性受到强烈抑制。聚合酶链式反应(PCR)表明SW1及蓝藻水华堆积处理池均含有mlrA的同源基因,表明处理池中存在MCs的生物降解。

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.