銅綠微囊藻毒素釋放之研究; Studies on toxin releasing of Microcystis aeruginosa

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Title:	銅綠微囊藻毒素釋放之研究;Studies on toxin releasing of Microcystis aeruginosa
Authors:	凃致道;Jyh-Douh Tu
Contributors:	生命科學研究所
Keywords:	毒素釋放;微囊藻;藍綠藻;微囊藻毒;產毒基因;toxin release;microcystin;McyH;microcystis;cyanobacteria
Date:	2007-07-06
Issue Date:	2009-09-22 10:20:13 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	銅綠微囊藻屬於藍綠藻（又稱藍綠菌）的一種，其水華特性及所產生具肝臟毒性的微囊藻毒均被廣泛地研究，一般認為微囊藻毒通常存在細胞內，細胞老化及死亡後分解才有釋放現象，然本研究發現過去實驗室所單離出的七株產毒微囊藻株中，其中M.TY-2、M.TN-3、M.TN-4這三株藻在對數成長期期間有釋放毒素到細胞外並且持續在培養基中累積的現象，而另外M.TN-2、M.CY-1、M.KS-15、M.KS-29 四株藻則沒有明顯的藻毒釋放現象，這些產毒的藻株裡，對毒素的釋放似乎存在不同程度的表現。由這些藻株裡，利用PCR放大及轉殖技術分析了產毒微囊藻生合成酵素基因組 (mcyA~J) 中包含ABC transporter ATPase（356th-469th）的 mcyH序列，經軟體操作轉成胺基酸序列後與實驗室前所分析的M.TY-1藻株及基因庫中的PCC7806進行序列比對，發現不同藻株間雖然存在數個不同的差異位置，但彼此間相似程度很高，而在ATPase序列中會影響主動運輸的活性區域胺基酸序列皆相同，僅在其他第389個胺基酸（離胺酸）及第427個胺基酸（麩胺酸）存在變異，然而這樣的變異，並無法歸納出其與毒素的有無釋放有關，而從整段McyH蛋白質的其他不同差異，也無法針對毒素釋放顯著差異的兩群藻株做出區分，此證明了微囊藻毒不同的釋放現象與McyH序列上的差異並無關係。 Microcystis aeruginosa, which is a well known blue-green alga (cyanobacterium), has been extensively studied for its bloom-forming characters and productions of the hepatotoxic microcystins. Microcystins are generally considered remaining within the cells and then releasing are generally considered to be the result of cell is integration due to stress and death. From our studies on the culture of M. aeruginosa clones, we found the toxins were accumulating in the cell-free medium during the log phase of growth in the clones of M.TY-2, M.TN-3 and M.TN-4, while it is absence in the culture of M.TN-2, M.CY-1, M.KS-15 and M.KS-29. Our toxin analysis in the medium showed two groups of clones that release toxin during the log phase or not. In these clones of M. aeruginosa, the sequence of McyH, which is one of microcystin synthetase (mcyA~J), was studied through PCR amplification and transgenic cloning, and then translated into amino acid sequences. Amino acid sequences of these clones were compared with that of previously studied M.TY-1 clone and PCC7806 in Genebank. It was found that the amino acid sequences, especially of McyH in these toxic clones of M. aeruginosa were highly conserved, except at few amino acid sites. From the results, we found that only two amino acid sites, 389th (glutamic acid) and 427th（lysine）amino acid, have mutation among the studied toxic M. aeruginosa clones. However, such mutations could not lead to the toxin releasing difference. By comparison of the amino acid sequence alignment of the entire McyH, the difference of the alignment was found to be no correlation to the toxin releasing ability.
Appears in Collections:	[Graduate Institute of Life Science] Electronic Thesis & Dissertation

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