環境因數對微囊藻毒性變化之影響

Abstract

本論文以有毒之銅綠微囊藻(Microcystis aeruginosa strain 298, NIES)?實驗材料。在實驗室培養確定其最佳生長條件?32℃、4000lux及pH 7.5 (td＝0.68 day)。經以老鼠生物分析法測定培養於不同的環境下之藻細胞，發現其毒性變化很大(LD50＝5.9?82.25 mg dry algae/kg mouse weight)。本實驗以微過濾及高效液相層析法自藻細胞中分離出兩種純的有毒物質（其分子量介於500?3000 D）。此二物質在波長238?240nm之間有最高之吸收值，且毒素之濃度和其於240 nm之吸光?呈線性相關。據此相關曲線可用?直接定量毒素濃度。除外，本論文並探討溫度、光度及酸鹼值(pH)等環境因數對微囊藻毒性及其所含之毒素成分及含量之影響。結果發現微囊藻毒性之強弱確受環境因數之影響，而毒性之強弱與生長之快慢成負相關。溫度對微囊藻的生長及毒性影響最大。酸鹼?對微囊藻之生長與毒性雖然亦有影響，但不及溫度對其之影響。光度對生長有明顯的影響，但對藻細胞的毒性，則除了在弱光與強光時稍弱外，幾乎沒有影響。以高效液相層析分析毒素組成，確定毒性的改變與毒素總量及毒素種類之含量比例有關。結果顯示，兩種藻毒中以毒素A的含量與藻細胞毒性較有關係。藻毒A之毒性(LD50＝10.1ug/kg mouse)大於毒素B (71 ug/kg mouse)，也比文獻上所述之其他微囊藻毒之性(LD50＝47?70ug/kg mouse)略高。

The effect of environmental factors on the toxicity of Microcystis aeruginosa was. studied. The growth conditions of a-toxic strain of Microcystis aeruginosa str. 298 was characterized. The optimum growth of cells was found to be under 32℃, 4000lux and pH 7.5. The toxicity of the cell assayed by mouse bioassay was various, LD50 varying from 5.9 to 82.25mg dry algae/kg mouse weight, when the growth condition was altered. The extraction of toxin from cell extract was performed by sonification and centrifugation. Two toxins were obtained by further purified with ultrafiltration and subsequent preparative HPLC. Both of the toxins had a molecular weight between 500 and 3000 daltons an absorption maximum at 238-240nm. The absorption of toxin at this wavelength show a linear relationship with the quantity of them, making it possible to quantify the toxin by measuring the quantitative absorption at the wavelength. The toxicity of cells was affected by various environmental factors, such as temperature, light intensity, and pH. The toxicity was higher when slower growth. Temperature markedly influenced the growth and toxicity of the cells, while light intensity exerted its effect majority on the growth of cells rather than on the toxicity of the cells. pH of culture medium also influenced the growth and toxicity of cells. However, its effect was apparantly smaller than temperature. HPLC quantitative analysis of toxins showed that the relative amounts of toxin A and B as well as the total toxin produced by the cells varied. Present-results pointed out that the variation in toxicity of the cells was related more to the amount toxin A than to-that of B. The further results of mouse bioassay indicated that the toxin A (10 ug/kg) was more toxic than toxin B (71 ug/kg). Toxin A was even more toxic than other microcystins ever reported.