title: Diverse genotypes of Bradyrhizobium nodulate herbaceous Chamaecrista (Moench) (Fabaceae, Caesalpinioideae) species in Brazil.
abstract: 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.
authors.affiliation: Programa de Pós-Graduação em Biotecnologia, Universidade Estadual de Feira de Santana, Brazil.
authors.forename: José Miguel Ferreira Dos
authors.initials: JM
authors.lastname: Santos
authors.affiliation: Programa de Pós-Graduação em Biologia e Biotecnologia de Microrganismos, Universidade Estadual de Santa Cruz, Brazil.
authors.forename: Patricia Alves
authors.initials: PA
authors.lastname: Casaes Alves
authors.affiliation: Programa de Pós-Graduação em Biologia e Biotecnologia de Microrganismos, Universidade Estadual de Santa Cruz, Brazil.
authors.forename: Verônica Cordeiro
authors.initials: VC
authors.lastname: Silva
authors.affiliation: Programa de Pós-Graduação em Biologia e Biotecnologia de Microrganismos, Universidade Estadual de Santa Cruz, Brazil.
authors.forename: Mariana Ferreira
authors.initials: MF
authors.lastname: Kruschewsky Rhem
authors.affiliation: The James Hutton Institute, Invergowrie, Dundee DD2 5DA, UK.
authors.forename: Euan K
authors.initials: EK
authors.lastname: James
authors.affiliation: Departamento de Ciências Agrárias e Ambientais, UESC-Universidade Estadual de Santa Cruz, Rod. Jorge Amado, Km 16, Ilhéus, BA 45662-900, Brazil. Electronic address: egross@uesc.br.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Gross
mesh_terms: D020369:Bradyrhizobium / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D001938:Brazil; D031288:Chamaecrista / Q000382:microbiology*; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics; D020043:Genes, Essential; D005838:Genotype; D010802:Phylogeny; D055170:Plant Root Nodulation; D018517:Plant Roots / Q000382:microbiology*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D013559:Symbiosis
chemical_list: D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D021903:DNA, Ribosomal Spacer; D012336:RNA, Ribosomal, 16S
keywords: Bradyrhizobium; Chamaecrista; Housekeeping genes; Nodule formation; Nodule ultrastructure; Phylogeny