红树林湿地希瓦氏菌W3的分离及腐殖质还原特性研究

Isolation and Characterization of a Humic-Reducing Bacterium Shewanella Strain W3 from Mangrove Sediment

从红树林湿地沉积物中分离到1株具有腐殖质还原能力的菌株W3,通过细胞形态、生理生化以及16SrDNA的分子生物学亲缘关系分析方法,确定该菌为希瓦氏菌属,命名为Shewanella sp.W3.W3菌能够利用乳酸钠、甲酸钠和丙酮酸钠作为电子供体进行腐殖质还原,在48h内对1mmol/LAQDS的还原率分别为96%、40%和10%.另外,菌体的生长与AQDS还原表现出相同的趋势,菌体数在60h达到最大值,约为1.77×108CFU/mL,比初始接种值约增殖了100倍,而未添加乳酸钠实验组的基本没有观察到AQDS的还原和菌体的增长.该菌进行腐殖质还原的最适pH范围为7～9,最适的NaCl浓度范围为5～30g/L,而最适温度范围为30～35℃.实验结果表明,该菌的腐殖质还原过程是生物化学反应过程,且能够在还原腐殖质的同时偶联能量的产生,支持菌体的生长.推测具有腐殖质还原的希瓦氏菌在元素的生物地球化学循环和环境微生物治理中具有潜在的应用价值.

A humus-reducing bacterium strain W3 was isolated from the mangrove sediment. Based on the analysis of morphology,physiobiochemical characteristics and 16S rDNA gene sequence,this strain was identified as Shewanella sp. W3. Strain W3 was able to reduce humic with lactate,formate and pyruvate as electron donor and the humic reduction rates to 1 mmol /L AQDS were 96% ,40% and 10% respectively within 48 hours. In addition,the bacteria can grow coupled with the humic reduction. Strain W3 grew to maximal density of 1. 77 × 10^8 CFU /mL after complete reduction of 1 mmol /L AQDS. However,the growth of strain W3 was light increase in the control experiment in the absence of electron donor. The optimal initial pH,NaCl concentration,and temperature for strain W3 reducing humic were pH 7-9,5-30 g /L,and 30-35℃ ,respectively. Combined experimental results showed that the humic reduction was a biochemical process and strain W3 could conserve energy to support growth from lactate oxidation coupled to humic reduction. It is suggested that humic reduction by Shewanella bacteria may play important roles in biogeochemical circulation of elements and have potential application in the microbial bioremediation to contaminations.