Conversion of Nitrite to Nitrate by Nitrite-resistant Yeasts

Candida species YK 11 and YK 92 and Geotrichum candidum YK 57, which were isolated as nitrite-resistants, converted nitrite in the culture medium to nitrate stoichiometrically during growth. The nitrite-oxidizing reaction was confirmed under aerobic conditions in the intact cell system with 15 mm nitrite, 150 mm glucose, and 100mm Tris-HCl buffer (pH 7.0). Glucose or other carbohydrate which supported the microbial growth was indispensable for the reaction. The rate of oxidation (0.9 ~ 1.3 × 10⁵ μg-N/g of YK 92 cells·day) and the maximum amounts of nitrate formed in the culture medium (200 mm, 2800 μg-N/ml) were much larger than those of other heterotrophic nitrifiers and almost the same as those of Nitrobacter.

The nitrite-oxidizing activity was demonstrated in many types of yeast species.     

绿豆Ty1/Copia类反转录转座子逆转录酶序列的克隆和分析

利用Ty1/copia类反转录转座子的保守位点设计简并引物,从绿豆(Vigna radiata(L.)Wilczek)基因组中扩增得到了反转录转座子的逆转录酶序列.对扩增得到的约270bp的片段进行分离和克隆,并随机挑选了40个克隆进行测序,结果得到了36个单独的核酸序列,其中18个含有移码突变或终止子.根据序列比对,这些克隆可分为9组以及单个的9种.这40个克隆中,核酸序列相似性从8%到100%,显示出其核酸序列的高度异质性.将这些克隆的核酸序列与来自其他种植物的相应序列进行谱系分析,发现有些克隆与来自其他种植物的相应序列的亲缘关系比这些克隆之间更为接近.斑点杂交显示Ty1/copia反转录转座子约占绿豆基因组的9.3%.     

水稻双子房突变体中类copia逆转座子同源序列的研究

以水稻双子房突变体的总ＤＮＡ为模板,用简并引物扩增类ｃｏｐｉａ逆转座子的逆转录酶区域。从ＰＣＲ产物中分离到代表３个不同的类ｃｏｐｉａ逆转座子的片段,其中两个在水稻（Ｏｒｙｚａ ｓａｔｉｖａ Ｌ．）品种“窄叶青８号”和“京系１７”间产生的多态性杂交带分别定位于水稻７条染色体的９个位点。Ｒ３３－８含大量的终止码,Ｒ３３－１及Ｒ３３－４为连续的编码区,推测的氨基酸序列含８１个氨基酸残基。Ｒ３３－１的拷贝