Development of bioremediation processes under anoxic conditions using denitrifying bacteria

1)反硝化条件下降解芳香族化合物的微生物群落分析在反硝化条件下降解芳香族化合物的细菌为限制菌，分别属于Thauera属和Azoarcus属。在这个项目中，我们分离了一些属于磁螺旋藻属的新菌株。采用16S rDNA进行系统发育分析，将分离菌株分为3个类群，分别对应生长所需芳香族化合物的可用性。(1) Thauera sp. DNT-1对甲苯的降解作用：该菌在好氧和反硝化条件下均能降解甲苯。克隆了甲苯双加氧酶（Tod）和琥珀酸苄酯合成酶（Bss）。从基因转录分析结果来看，Bss仅在厌氧条件下有效，而tod基因产物在有氧条件下起作用。(2)磁螺旋藻（Magnetospirillum sp. TS-6）降解甲苯基因的克隆。从磁螺旋藻TS-6中克隆了反硝化条件下参与降解甲苯主要酶的编码基因。由此可以确定该生物的降解途径。3)原位生物修复条件下反硝化菌的分配苯甲酰辅酶a还原酶是多种厌氧甲苯降解物发生环裂变的关键酶。提出了一种以苯甲酰辅酶a还原酶基因为探针的厌氧芳香族化合物降解物监测系统。

1) Analysis of microbial consortia for degradation of aromatic compounds under denitrifying conditionsBacteria that degrade aromatic compounds under denitrifying conditions had been restricted strains belonging to genera Thauera and Azoarcus. In this project, we have isolated a number of novel bacterial strains that belonged to genus Magnetospirillum. The isolates were divided into 3 groups through phylogenetic analysis with 16S rDNA, which correspond to availability of aromatic compounds for growth.2) Pathway for degradation of aromatic compounds by the isolates(1) Toluene degradation by Thauera sp. DNT-1: The organism was found to be able to degrade toluene under both aerobic and denitrifying conditions. Toluene dioxygenase (Tod) and benzyl succinate synthase (Bss) were cloned. From the results of transcriptional analyses of the genes, Bss could be effective only under anaerobic conditions, while tod gene product functioned under aerobic conditions.(2) Cloning of genes for toluene degradation by Magnetospirillum spp. The genes encoding main enzymes participating in toluene degradation under denitrifying conditions were cloned from Magnetospirillum sp. TS-6. From the result, the degradation pathway of the organism could be confirmed.3) Assignment of the denitrifying bacteria under in-situ-bioremediationBenzoyl CoA reductase was found as a key enzyme for the ring fission a variety of anaerobic toluenedegraders. We proposed a monitoring system for anaerobic aromatic-compound-degraders using benzoyl CoA reductase genes as the probe.