滇池沉积物菌群对微囊藻毒素的厌氧生物降解

Anaerobic Biodegradation of Microcystin by Bacterial Community from Sediment of Dianchi Lake

好氧微生物降解已经被证明是微囊藻毒素(MC)自然转化的主要途径,但是厌氧降解的作用尚不明确.为了揭示这一降解过程,研究了滇池沉积物中混合菌群在厌氧条件下对MCLR的降解能力,并考察了环境因素和外加营养源对该过程的影响.结果表明,厌氧条件下MCLR在2 d内从5 mg/L迅速降解到检测限以下,说明该菌群在厌氧条件下对MCLR具有较强的降解能力,并且可以利用MCLR作为唯一氮源.在实验温度范围内,MCLR的降解速率随着温度的升高而增大.酸性条件下MCLR的厌氧降解缓慢(pH=5.0)甚至停止(pH=3.0),而中性(pH=7.0)和碱性(pH为9.0、11.0)条件下降解速率没有显著差异.单独添加葡萄糖可以产生酸性物质而使体系的pH下降,从而抑制MCLR的降解,但是同时添加硝酸盐可以消除这一影响.单独添加硝酸盐对MCLR的厌氧降解也有显著的抑制作用,说明硝酸根在这一过程中未被MCLR厌氧降解菌用作最终电子受体.以上结果表明,厌氧降解可能是沉积物中MCLR转化的另一重要途径,该过程在MCLR污染治理方面具有潜在的应用价值.

Aerobic biodegradation has been identified as the main attenuation mechanism for microcystin,but the role of anaerobic microcystin biodegradation remains unclear.To elucidate this process,we assessed the potential for anaerobic microcystin LR biodegradation by sediment microbial community from Dianchi Lake and evaluated the effects of environmental factors and additional nutrient sources on the rates of anaerobic biodegradation.The results showed that microcystin LR was rapidly degraded from 5 mg/L to below detection limit within 2 days,demonstrating that the indigenous microorganisms can efficiently degrade microcystin LR under anaerobic conditions and can use microcystin LR as a sole nitrogen source.The rates of anaerobic microcystin LR biodegradation increased with increasing incubation temperature within the experimental range of 15-30℃. Anaerobic microcystin LR biodegradation was slower（pH=5.0） or even ceased（pH=3.0） at acidic pH,but there was no difference in the rates at neutral（pH=7.0） and alkaline（pH 9.0,11.0） conditions.The addition of glucose decreased pH of the culture by producing acidic compounds and therefore significantly inhibited the anaerobic biodegradation of microcystin LR,but with the addition of NO3^-,this inhibition disappeared.NO3^- amendment also retarded the biodegradation of microcystin LR,demonstrating that NO3^- was not used as a terminal electron acceptor.These findings suggest that anaerobic biodegradation might be another main attenuation mechanism for microcystin LR in sediments and present a significant bioremediation potential.