养虾池好氧反硝化细菌新菌株的分离鉴定及特征

Isolation and characterization of a novel aerobic denitrifier from shrimp pond

利用间歇曝气选择性富集并对所获菌株的好氧反硝化活性进行检测。筛选到一株亚硝酸盐去除活性较高的好氧反硝化细菌。在溶解氧（D0）为3.80-5．21mg／L的培养条件下。该菌株10h内将亚硝态氮由26．18mg／L降至0；在盐度为0—25之间20h内均可达到同样的去除效果。通过形态学特征、生理生化反应及部分长度16SrDNA序列分析对筛选菌株进行鉴定，初步判定它为嗜麦芽寡养单胞菌Stertotrophomonas maltophilia。亚硝酸盐还原酶基因分析结果表明。该菌株只含亚硝酸盐还原酶nitS基因，其序列与Alcaligenes faecalis A15（后来被重新鉴定为Pseudomonas stutzeri）的nirS基因序列相似。

Denitrifying activity of most typical denitrifiers is usually completely suppressed when anaerobiosis is insufficient, aerobic denitrifying bacteria has a major advantage in reducing nitrate and/or nitrite to N2 under aerobic conditions, which is ertical for nitrite and nitrate removal from aerobic environment, such as aquaculture water. Aims： To isolate aerobic denitrifying bacteria to enhance nitrate and nitrite removal from aquaculture system. Methods and Results ： Selective enrichment culture method under alternating oxic-anoxic conditions was used for screening bacteria that have high capability of aerobic denitrification from a shrimp pond. A novel denitrifier X0412 was isolated and purified after 2 months of incubation. It, identified as Stenotrophomonas mahophilia （formerly referred to as Xanthomonas maltophilia） based on its biochemical and morphological characters, is grouped into the γ subclass of the class Proteobacteria. Phylogenetic analysis of 16S rDNA sequences indicated that strain X0412 was most closely related to S. maltophilia AB021406. Analysis of the both nitrite reductase genes nirS and nirK showed that it contained nirS gene, which is highly homologous to nirS of Pseudomonas stutzeri （formerly referred to as Alcaligenes faecalis A15）. When bacterial concentrations as represented by OD600 increased from 0. 044 to 0. 436, the bacterium reduced the concentrations of nitrite rapidly from 26.18 mgL^-1 to an undetectable level within 10 h, with DO titer decreasing from 5.21 mgL^-1 to 3.80 mgL^-1 Similar result was observed within 20 h at the salinity less than 25%0 . Conclusions： Stenotrophomonas maltophilia strain X0412 reduced nitrite rapidly and efficiently at a high DO concentration and across a wide range of salinity. Significance and Impact of the study： Strain X0412 is highly promising for future potential application in the control of nitrite and nitrate concentration of aquaculture systems.