The genus Micromonospora has been found in nodules of several legumes and some new species of this genus were isolated from these plant organs. In this study we analysed the taxonomic diversity of Micromonospora strains isolated from alfalfa nodules in Spain and Australia on the basis of three phylogenetic markers, the rrs and gyrB genes and 16S-23S intergenic spacer (ITS). The genome analysis of selected strains representative of different clusters or lineages found after rrs, gyrB and ITS analyses confirmed the results obtained with these phylogenetic markers. They showed that the analysed strains belong to at least 18 Micromonospora species including previously described ones, such as Micromonospora noduli, Micromonospora ureilytica, Micromonospora taraxaci, Micromonospora zamorensis, Micromonospora aurantiaca and Micromonospora tulbaghiae. Most of these strains belong to undescribed species of Micromonospora showing the high taxonomic diversity of strains from this genus inhabiting alfalfa nodules. Although Micromonospora strains are not able to induce the formation of these nodules, and it seems that they do not contribute to fix atmospheric nitrogen, they could play a role related with the mechanisms of plant growth promotion and pathogen protection presented by Micromonospora strains isolated from legume nodules.

属小单已经在几个豆类和该属的一些新品种的结节被发现从这些植物器官隔离。在这项研究中，我们基于三种系统发育标记，rrs和gyrB基因以及16S-23S基因间隔子（ITS），分析了从西班牙和澳大利亚的苜蓿小结节中分离得到的微单孢菌菌株的分类学多样性。在rrs，gyrB和ITS分析后发现的代表不同簇或谱系的选定菌株的基因组分析，证实了使用这些系统发育标记所获得的结果。他们表明，所分析的菌株至少属于18个单孢菌物种，包括先前所描述的，如小单孢noduli，小单孢ureilytica，小单孢蒲公英，小单孢zamorensis，小单孢aurantiaca和小单孢tulbaghiae。这些菌株中的大多数属于未描述的小单孢菌属物种，显示出来自该属苜蓿根瘤的该菌株的高分类学多样性。虽然微单孢菌菌株不能诱导这些根瘤的形成，似乎它们对固定大气中的氮没有贡献，它们可能与从豆类根瘤中分离出的微单孢菌菌株提供的促进植物生长和病原体保护的机制有关。