Frankia菌遗传多样性的rDNAIGS RFLP研究

Frankia是一类能与非豆科树木共生结瘤固氮的放线菌。关于其属的分类目前比较确认 ,对于种水平的划分 ,虽然从可溶性蛋白类型 (张道海等 ,1 991 ;Bensonetal.,1 983;Gardesetal.,1 987a)、同功酶类型(Gardesetal.,1 987b ;张道海等 ,1 989)、脂肪酸 (Weeleretal.,1 986)、血清 (Bakeretal.,1 981 ;孙慧君等 ,1 991 )、宿主特异性 (Baker,1 987;Torreyetal.,1 989)、DNA同源性 (Fermamdexetal.,1 989;Akimovetal.,1 992 )、基因组 (Dobritsa ,1 985 )和质粒的限制酶切图谱 (Simonetetal.,1 985 )等诸多方面进行了分析 ,但由于研究的菌株数量有限 ,且培养过程中菌株的生物学特性易发生变异 ,因而迄今为止仍没有一种有效的种的分类方法。近年来 ,1 6SrDNA及其 1 6S～ 2 3SrDNA间隔序列作为一个分子标记 ,广泛应用于各种微生物的分子遗传差异和分类鉴定研究 (韦革宏等 ,1 999;冯瑞华 ,2...

DIVERSITY OF ACTINORHIZAL FRANKIA BY rDNA IGS RFLP ANALYSIS

DNA extracted directly from the living nodules of Casuarina cunninghamiana, C.collina, C.glauca, Alnus cremastogyne, A.trabeculosa and Myrica rubra and also from 21 Frankia strains isolated from the root nodules of the actinorhizal plants in Fujian, including C. cunninghamiana, C.equisetifolia, C.glauca, A.cremastogyne and M.rubra. PCR amplification was conducted with the primers targeting the 3' end of the 16S rDNA, the IGS, and the 5' part of the 23S rDNA (i.e.,rrn region). PCR products were then analyzed by using a set of restriction endonucleases. Two distinct genetic groups were recognized on the basis of these restriction patterns. All Frankia strains associated with the host species of Casuarina were assigned to the same group. Frankia living in the nodules of Myrica and Alnus belonged to the other group. In Myrica-Alnus group, there was two sub-group which one included A.cremastogyme and the other contained A.trabeculosa and M.rubra. The results of RFLP analysis showed that the genetic diversity of Frankia associated with Casuarina could be lower, but Frankia existed in the soils of Fujian Province would have more richness in genetic diversity. The results also reflected that host plant has an ability to choose the strains to form a symbiont.