Segovia L, Young J P, Martínez-Romero E
Departamento de Genética Molecular, Universidad Nacional Autónoma de México, Cuernavaca, Morelos.
Int J Syst Bacteriol. 1993 Apr;43(2):374-7. doi: 10.1099/00207713-43-2-374.
A new Rhizobium species that nodulates Phaseolus vulgaris L. is proposed on the basis of a sequence analysis of 16S ribosomal DNA. This taxon, Rhizobium etli sp. nov., was previously named Rhizobium leguminosarum biovar phaseoli (type I strains) and is characterized by the capacity to establish an effective symbiosis with bean plants, the reiteration of the nitrogenase structural genes, the organization of the common nodulation genes into two separate transcriptional units bearing nodA and nodBC, the presence of the polysaccharide inhibition gene, psi, and the 16S ribosomal DNA sequence. An analysis of the sequence of a fragment of the 16S rRNA gene shows that this gene is quite different from the gene of R. leguminosarum. In addition, all R. etli strains have identical sequences. We describe these analyses and discuss additional evidence supporting our proposal.
基于对16S核糖体DNA的序列分析，提出了一种能使菜豆结瘤的新根瘤菌物种。这个分类单元，即新种菜豆根瘤菌（Rhizobium etli sp. nov.），以前被命名为菜豆根瘤菌生物型菜豆（I型菌株），其特征在于能够与豆科植物建立有效的共生关系、固氮酶结构基因的重复、共同结瘤基因组织成两个分别携带nodA和nodBC的独立转录单元、多糖抑制基因psi的存在以及16S核糖体DNA序列。对16S rRNA基因片段序列的分析表明，该基因与菜豆根瘤菌的基因有很大不同。此外，所有菜豆根瘤菌菌株都具有相同的序列。我们描述了这些分析，并讨论了支持我们提议的其他证据。
