以转座子Tn5作弗氏中华根瘤菌的可识别生态学标记的研究──Tn5的水平转移及其对R．fredii　Tn5突变株运动的影响

Transposon Tn5 used as an identifiable ecological marker of R. fredii stains: Horizontal transfer frequency or transponson Tn5 and its influence on the movement of R. fredii Tn5 mutant

将一株弗氏中华根瘤菌（Ｒ．ｆｒｅｄｉｉ）ＱＢ１１３０的Ｔｎ５插入突变株ＯＮ－２用于生态学研究，以评估Ｔｎ５在自然环境中的水平转移以及各种水势下Ｔｎ５对突变株ＯＮ－２在土壤中运动的影响．试验表明，在自然潮湿的土壤中，Ｔｎ５本身的水平转移频率很低，且与Ｔｎ５插入相关的突变株卡那霉素抗性表型标记在非选择性平板上连续传４０代后仍然稳定．突变株ＯＮ－２与相对应的野生型菌株ＱＢ１１３０在各种相同水势的土壤中的运动无明显差异（Ｐ＝０．０１），表明Ｔｎ５的插入不影响突变株的运动．因此，Ｔｎ５可作为研究Ｒ．ｆｒｅｄｉｉ基因工程菌大回应用的一个稳定有效的生态学标记．

A transposon Tn5 insertion mutant ON-2 of Rhizobium, fredii wild strain QB1130 was used in ecological study to evaluate the probability of horrizontal transfer of transposon Tn5 in natural environments and its influence on the movement of mutants. The results show that the horrizontal transfer frenquency of Tn5 is very low in natural moist soil. The Km'phenotype of the mutant associated with Tn5 insertion is shown to be stable after growth for over 40 generations on nonselective media. No significant difference(P=0. 01) between the movements of the mutant and its corresponding wild type was found, which implies that transponson Tn5 does not influence the movement of Tn5 mutant. The study suggests that Tn5 can be selected as a stable ecological marker in monitoring R. fredii genetic engineering strains used in the field.