Santos José Miguel Ferreira Dos, Casaes Alves Patricia Alves, Silva Verônica Cordeiro, Kruschewsky Rhem Mariana Ferreira, James Euan K, Gross Eduardo
Programa de Pós-Graduação em Biotecnologia, Universidade Estadual de Feira de Santana, Brazil.
Programa de Pós-Graduação em Biologia e Biotecnologia de Microrganismos, Universidade Estadual de Santa Cruz, Brazil.
Syst Appl Microbiol. 2017 Mar;40(2):69-79. doi: 10.1016/j.syapm.2016.12.004. Epub 2017 Jan 10.
The genus Chamaecrista comprises more than 330 species which are mainly distributed across tropical America, especially in Brazil (256 spp.), the main center of radiation. In this study, nodulation of herbaceous Chamaecrista species that are commonly found growing in different vegetation types in the north eastern Brazilian state of Bahia was assessed together with the diversity of rhizobia isolated from their root nodules. Genetic characterization of the isolates was performed using molecular markers to examine the phylogeny of their "core" (16S rRNA, ITS, recA, glnII, dnaK and gyrB) and symbiosis-related (nifH, nodC) genomes. Nodule morphology, anatomy and ultrastructure were also examined, as was the capacity of the isolates to form nodules on Chamaecrista desvauxii and siratro (Macroptilium atropurpureum). Analysis of 16S rRNA gene sequences demonstrated that the isolates belonged to seven clusters within the genus Bradyrhizobium, and more detailed analyses using sequences of the ITS region and concatenated housekeeping genes grouped the Chamaecrista rhizobia by vegetation type and plant species. These analyses also suggested some potentially novel Bradyrhizobium species, which was corroborated by analyses of their nifH and nodC sequences, as these formed separated branches from all Bradyrhizobium type strains. All the 47 strains tested produced effective nodules on C. desvauxii but none on siratro. Chamaecrista nodules are herein described for the first time in detail: they are indeterminate and structurally similar to others described in the Caesalpinioideae, with infection threads in the invasion and nitrogen fixation zones, and with both infected and uninfected (interstitial) cells in the nitrogen fixation zone.
合萌属包含330多种植物，主要分布于热带美洲，尤其是巴西（256种），这里是该属植物的主要辐射中心。在本研究中，对巴西东北部巴伊亚州不同植被类型中常见的草本合萌属植物的结瘤情况进行了评估，并对从其根瘤中分离出的根瘤菌多样性进行了研究。使用分子标记对分离菌株进行遗传特征分析，以研究其“核心”基因组（16S rRNA、ITS、recA、glnII、dnaK和gyrB）和共生相关基因组（nifH、nodC）的系统发育。还研究了根瘤的形态、解剖结构和超微结构，以及分离菌株在德氏合萌和大翼豆（紫花大翼豆）上形成根瘤的能力。16S rRNA基因序列分析表明，分离菌株属于慢生根瘤菌属的七个簇，使用ITS区域序列和串联持家基因进行的更详细分析，根据植被类型和植物种类对合萌根瘤菌进行了分类。这些分析还表明存在一些潜在的新慢生根瘤菌物种，对其nifH和nodC序列的分析证实了这一点，因为这些序列与所有慢生根瘤菌模式菌株形成了单独的分支。所有测试的47个菌株都能在德氏合萌上产生有效的根瘤，但在大翼豆上均不能结瘤。本文首次详细描述了合萌根瘤：它们是不定型的，结构上与云实亚科中描述的其他根瘤相似，在侵入和固氮区域有感染丝，在固氮区域有受感染和未受感染（间隙）的细胞。
