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首页> 美国卫生研究院文献>Applied and Environmental Microbiology >Diversity of Plasmid Profiles and Conservation of Symbiotic Nitrogen Fixation Genes in Newly Isolated Rhizobium Strains Nodulating Sulla (Hedysarum coronarium L.)
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Diversity of Plasmid Profiles and Conservation of Symbiotic Nitrogen Fixation Genes in Newly Isolated Rhizobium Strains Nodulating Sulla (Hedysarum coronarium L.)

机译：新分离的根瘤菌（Hedysarum coronarium L.）新分离的根瘤菌菌株中质粒谱的多样性和共生固氮基因的保守性

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Forty-five Rhizobium strains nodulating sulla (Hedysarum coronarium L.), isolated from plants grown in different sites in Menorca Island and southern Spain, were examined for plasmid content and the location and organization of nif (nitrogen fixation) and nod (nodulation) sequences. A great diversity in both number and size of the plasmids was observed in this native population of strains, which could be distributed among 19 different groups according to their plasmid profiles. No correlation was found between plasmid profile and geographical origin of the strains. In each strain a single plasmid ranging from 187 to 349 megadaltons hybridized to Rhizobium meliloti nifHD and nodD DNA, and in three strains the spontaneous loss of this plasmid resulted in the loss of the nodulation capacity. In addition to the symbiotic plasmid, 18 different cryptic plasmids were identified. A characteristic cryptic plasmid of >1,000 megadaltons was present in all strains. Total DNA hybridization experiments, with nifHD and portions of nodC and nodD genes (coding for common nodulation functions) from R. meliloti as probes, demonstrated that both the sequence and organization of nif and common nod genes were highly conserved within rhizobia nodulating sulla. Evidence for reiteration of nodD sequences and for linkage of nodC to at least one copy of nodD was obtained for all the strains examined. From these results we conclude that Rhizobium strains nodulating sulla are a homogeneous group of symbiotic bacteria that are closely related to the classical fast-growing group of rhizobia.
机译：从在梅诺卡岛和西班牙南部不同地点生长的植物中分离出的45种根瘤菌根瘤菌（Hedysarum coronarium L.）被检查了质粒的含量以及nif（固氮）和nod（结瘤）序列的位置和组织。 。在该菌株的天然种群中观察到质粒的数量和大小都有很大的差异，可以根据它们的质粒概况在19个不同的组中分布。在质粒图谱和菌株的地理起源之间未发现相关性。在每个菌株中，一个与杂根瘤菌nifHD和nodD DNA杂交的质粒介于187至349兆道尔顿之间，而在三个菌株中，该质粒的自发丧失导致结瘤能力的丧失。除共生质粒外，还鉴定了18种不同的隐性质粒。在所有菌株中均存在＞ 1,000兆道尔顿的特征性密码质粒。总DNA杂交实验以nifHD以及来自苜蓿根瘤菌的部分nodC和nodD基因（编码常见的结瘤功能）作为探针，证明nif和常见的nod基因的序列和组织在根瘤菌结节性沙勒菌中高度保守。对于所有检查的菌株，获得了重复nodD序列并将nodC与至少一个nodD拷贝连接的证据。从这些结果可以得出结论，结瘤性沙雷氏菌的根瘤菌是一组同质共生细菌，与经典的快速生长的根瘤菌密切相关。

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