| 摘要: | 本研究希望能由台灣的戴奧辛污染土壤，尋找出戴奧辛分解菌，並透過菌種的生化特性分析與污染物強化培養基的測試，達到分解菌的篩選、分離與馴化之目的。 本研究自污染場址下游採集的三個土壤樣品，戴奧辛毒性當量濃度最高為2450 ng-TEQ/kg。由菌源取出的菌株經過培養與分離後，分離鑑定出四株能存活於含有戴奧辛之培養基中，其菌株分別為Achromobacter xylosoxidans、Ochrobactrum anthropi、Ralstonia mannitolilytica和Agromyces sp.。本次研究所篩選出來的菌株，皆屬於革蘭氏陰性菌，外型為桿菌，其中以Ochrobactrum anthropi及Agromyces sp.菌體的長度約2μm，寬約1μm為最大。親緣演化分析結果顯示，Agromyces sp.與五氯酚分解菌Mycobacterium chlorophenolicum PCP-1親緣較接近，確認親緣可信度的Bootstrap value有95，代表此結果是可信的。 在分解菌生長與戴奧辛降解分析方面，本次研究所篩選的四株戴奧辛分解菌，需外添加1000 mg/L的葡萄糖，分解菌生長才不受培養基中戴奧辛(10μg/kg 2,3,7,8-TCDD)抑制。生長動力分析結果顯示，Achromobacter xylosoxidans及Ochrobactrum anthropi的最大比生長率，約0.115h-1。基質親和力的分析結果顯示，Ralstonia mannitolilytica 有最小基質親和力(Ks)，其值為43.2mg/L，代表此菌株對於基質的依賴性較小。抑制係數則是以Ochrobactrum anthropi的0.948mg/L為最大。 戴奧辛降解測試結果顯示，四菌株皆有戴奧辛降解的效果，且都是以好氧為主要途徑。此外，實驗結果顯示Achromobacter xylosoxidans、Ochrobactrum anthropi、Agromyces sp.三菌株，皆在適應期便有明顯降解2,3,7,8-TCDD的效果，但Ralstonia mannitolilytica需到生長期，2,3,7,8-TCDD濃度才有明顯變化。在這四株分解菌中，以Agromyces sp.的降解效果最佳，能使2,3,7,8-TCDD濃度下降97%。另外，透過蛋白質體分析發現，Achrom- obacter xylosoxidans受2,3,7,8-TCDD的影響，分子量40及50kDa的蛋白質濃度有增加的情形，Ochrobactrum anthropi亦有相同情況。Ralstonia mannitolilytica除120kDa的蛋白質外，其餘部份皆受戴奧辛的影響而減少了，其原因需進一步釐清，Agromyces sp. 的結果稍有不同，受2,3,7,8-TCDD影響後，改變的蛋白質為20及120kDa。 The objective of this study was to isolate the indigenous dioxin-degrading bacteria of Taiwan. Also, the characteristics of these bacteria were investigated after isolation followed by culture enrichment and strains acclimation. Three soil samples were gathered from the downstream of the announced dioxin and contamination site. The analytical results of PCDDs/PCDFs and their isomer concentration in all samples confirmed the dioxin contamination of the sampling site with the highest total toxic equivalence of 2450 ng-TEQ/kg of the contaminants. Four bacteria strains which can survive in dioxin media were isolated after sub-culture inoculation. The four strains were identified as Achromobacter xylosoxidans, Ochrobactrum anthropi, Ralstonia mannitolilytica and Agromyces sp.. It was found that all of the strains are gram’s negative in the morphology. In addition, Ochrobactrum anthropi and Agromyces sp. demonstrated the largest configuration with length 2 μm and width 1 μm. Particularly, Agromyces sp. had closest relationship to the PCP-degrading bacterium Mycobacterium chlorophenolicum PCP-1 according to phylogenetic analysis (bootstrap value = 95). The microbial growth kinetics showed that Achromobacter xylosoxidans and Ochrobactrum anthropi had the maximum specific growth rate of 0.115 h-1. Ralstonia mannitolilytica had the smallest half-saturation constants of 43.2 mg/L, meaning least dependence of substrate. Ochrobactrum anthropi has the greatest substrate inhibition coefficient of 0.948 mg/L. However, the microbial growth tests revealed that adding extra carbon source of glucose (1000 mg/L) to the culture medium containing high dioxin concentration (10 μg/kg 2,3,7,8-TCDD) would decrease the growth inhibition. Achromobacter xylosoxidans, Ochrobactrum anthropi, Agromyces sp. could degrade 2,3,7,8-TCDD at lag phase, whereas Ralstonia mannitolilytica decomposed it primarily at log phase. It was also observed that Agromyces sp. had the maximum 2,3,7,8-TCDD degradation efficiency (97%). The results of proteome analysis suggested that two primary proteome molecular weight of 40 and 50kDa for Achromobacter xylosoxidans and Ochrobactrum anthropi had changed during degradation of 2,3,7,8-TCDD. By contrast, 120 kDa proteome of Ralstonia mannitolilytica as well as 20 and 120 kDa proteome of Agromyces sp. would increase when 2,3,7,8-TCDD was degraded. |
