木麻黄共生固氮菌Frankia的分离鉴定及固氮效应

Identification and nitrogen fixation effect of symbiotic Frankia spp.isolated from Casuarina spp

从浙江省短枝木麻黄(Casuarina equisetifolia)和细枝木麻黄(C.cunninghamiana)的根瘤中共分离获得14株共生菌株。形态观察表明,菌株具有分枝状菌丝、多腔孢囊、泡囊等典型的Frankia结构、16SrDNA测序结果表明,供试菌株均为Frankia,其中4株属于生理类群A,7株属于生理类群B,3株属于生理类群AB。固氮效应研究表明,菌株均具有固氮酶生物学活性,但菌株之间存在显著差异,其中菌株ZCN192固氮酶活性最强,可达2.897μmol·mg-1·h-1,菌株ZCN199最低,固氮酶活性为0.056μmol·mg-1·h-1。活体固氮试验显示,与阴性对照相比,供试菌株能显著提高苗高、地径和干重,且一般情况下,离体固氮酶活性强的菌株在活体接种时能获得更明显的固氮效应。

A total of 14 symbiotic bacterial strains were isolated from the root nodules of Casuari- na equisetifolia and C. cunninghamiana in Zhejiang Province. All the strains exhibited typical Frankia morphological characteristics, including filamentous hyphae, vesicles, and multilocular sporangia borne terminally or in intercalary position. The 16S rDNA sequencing showed that all the strains were of Frankia, 4 of them belonging to physical group A, 7 belonging to physical group B, and the other 3 belonging to physical group AB. All the strains presented nitrogenase activity, but the activity differed significantly with the strains. Strain ZCN192 had the highest nitrogenase activity （2. 897 μmol·mg^-1· h^-1）, while ZCN199 had the lowest one （0. 056 μmol·mg^-1· h^-1 ）. After in vivo inoculated with all the strains, the plant height, basal diameter, and dry biomass of C. equisetifolia and C. cunninghamiana increased significantly, and overall, the strains with higher nitrogenase activity exhibited more obvious nitrogen fixation effect in vivo.