Shewanella sp.抗重金屬鎘與類金屬碲機制之探討

Cadmium resistance and tellurite resistance in Shewanella sp. isolated from environment

蔡孟儒(Meng-Ru Tsai)

指導教授 ： 簡志青

元智大學/工程學院/生物科技與工程研究所/碩士(2008年)

摘要

本研究探討自重金屬汙染的土壤裡分離出來可抵抗類金屬碲的微生物。加入1000μM的碲濃度在LB medium用以篩選在台南二仁溪流域附近泥土能夠抵抗類金屬碲之微生物。經過分離篩選後得到菌株TeC，並利用16S rDNA定序分析，發現其結果顯示此菌株屬於Shewanella sp.。實驗中也發現，此菌株的確能夠抵抗較高濃度之碲，文獻指出當菌株能夠生長及還原碲時，菌液的顏色將會轉成深黑色，此為較高價碲遭菌體還原成較低價碲的表現；而此菌株在含有鎘的環境下也能夠生長。
因此本實驗主要探討此菌株對於抵抗此兩種金屬元素是否具有相關性，因此利用了轉位子突變法針對存在於genomic DNA中能夠抵抗此兩種元素的基因進行突變。經突變後的菌株，培養在含有碲的培養基中發現，其還原較高價碲後顏色比對有明顯變淺，而另外一突變株則是對於鎘的抵抗能力有明顯的下降。之對於轉位子破壞基因之鑑定，以進行此菌株抵抗重金屬鎘與類金屬碲機制之探討

關鍵字

重金屬 ； 碲 ； 鎘

並列摘要

Bacteria isolated from Er-Ren River, Tainan by enrichment culture were studied for their ability to resist tellurite and cadmium. One of the isolates, Shewanella sp. strain TeC, was able to tolerate relative high concentration of tellurite and cadmium in the culture medium. Black precipitates occurred in strain TeC after growth in the medium containing tellurite indicating the reduction of tellurite to tellurium. The aim of this studied therefore was to generate mutants of strain TeC by transposon mutagenesis to study genes involved in tellurite resistance, tellurite reduction and/or cadmium resistance, respectively.

Mutants of TeC were screened for lost the ability of Cd resistance or tellurite reduction by Tn5 mutagenesis. Two mutants were selected for these traits. Mutant strain B21 was selected as Cd-sensitive mutant while mutant strain A8 showed a reduced ability for tellurite reduction compared to that of strain TeC. The characteristics of these two mutant strains for their tolerance to tellurite and cadmium as well as their ability for tellurite reduction (as measured by using diethyldithiocarbamate) compare to that of TeC were described in this thesis. Genes involved in the cadmium resistance and tellurite reduction (i.e. genes knockout by Tn5) remained to be determined.

並列關鍵字

Heavy metal ； Tellurite ； Cadmium ； Shewanella

參考文獻

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