title: Analysis of genomic diversity among photosynthetic stem-nodulating rhizobial strains from northeast Argentina.
abstract: The genomic diversity among photosynthetic rhizobia from northeast Argentina was assessed. Forty six isolates obtained from naturally occurring stem and root nodules of Aeschynomene rudis plants were analyzed by three molecular typing methods with different levels of taxonomic resolution: repetitive sequence-based PCR (rep-PCR) genomic fingerprinting with BOX and REP primers, amplified 16S rDNA restriction analysis (ARDRA), and 16S-23S rDNA intergenic spacer-restriction fragment length polymorphism (IGS-RFLP) analysis. The in vivo absorption spectra of membranes of strains were similar in the near infrared region with peaks at 870 and 800 nm revealing the presence of light harvesting complex I, bacteriochlorophyll-binding polypeptides (LHI-Bchl complex). After extraction with acetone-methanol the spectra differed in the visible part displaying peaks belonging to canthaxanthin or spirilloxanthin as the main carotenoid complement. The genotypic characterization by rep-PCR revealed a high level of genomic diversity among the isolates and almost all the photosynthetic ones have identical ARDRA patterns and fell into one cluster different from Bradyrhizobium japonicum and Bradyrhizobium elkanii. In the combined analysis of ARDRA and rep-PCR fingerprints, 7 clusters were found including most of the isolates. Five of those contained only photosynthetic isolates; all canthaxanthin-containing strains grouped in one cluster, most of the other photosynthetic isolates were grouped in a second large cluster, while the remaining three clusters contained a few strains. The other two clusters comprising reference strains of B. japonicum and B. elkanii, respectively. The IGS-RFLP analysis produced similar clustering for almost all the strains. The 16S rRNA gene sequence of one representative isolate was determined and the DNA sequence analysis confirmed the position of photosynthetic rhizobia in a distinct phylogenetic group within the Bradyrhizobium rDNA cluster.
authors.affiliation: Cátedra de Microbiologia Agricola, Facultad de Agronomía, Universidad de Buenos Aires and Instituto de Investigaciones Bioquímicas y Fisiológicas/Banco Nacional de Microorganismos (CONICET), Argentina.
authors.forename: Marcela S
authors.initials: MS
authors.lastname: Montecchia
authors.forename: Norma L
authors.initials: NL
authors.lastname: Kerber
authors.forename: Norma L
authors.initials: NL
authors.lastname: Pucheu
authors.forename: Alejandro
authors.initials: A
authors.lastname: Perticari
authors.forename: Augusto F
authors.initials: AF
authors.lastname: García
mesh_terms: D001118:Argentina; D015373:Bacterial Typing Techniques; D002338:Carotenoids / Q000378:metabolism; D016172:DNA Fingerprinting / Q000379:methods; D004269:DNA, Bacterial / Q000032:analysis*; D021903:DNA, Ribosomal Spacer / Q000032:analysis; D007887:Fabaceae / Q000382:microbiology*; D005838:Genotype; D008969:Molecular Sequence Data; D010788:Photosynthesis; D010802:Phylogeny; D018517:Plant Roots / Q000382:microbiology; D016133:Polymerase Chain Reaction / Q000379:methods; D012150:Polymorphism, Restriction Fragment Length; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012338:RNA, Ribosomal, 23S / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics; D012231:Rhizobium / Q000145:classification* / Q000235:genetics*; D017422:Sequence Analysis, DNA
chemical_list: D004269:DNA, Bacterial; D021903:DNA, Ribosomal Spacer; D012336:RNA, Ribosomal, 16S; D012338:RNA, Ribosomal, 23S; D002338:Carotenoids