RESUMEN
Forty-eight Burkholderia isolates from different land use systems in the Amazon region were compared to type strains of Burkholderia species for phenotypic and functional characteristics that can be used to promote plant growth. Most of these isolates (n=46) were obtained by using siratro (Macroptilium atropurpureum - 44) and common bean (Phaseolus vulgaris - 2) as the trap plant species; two isolates were obtained from nodules collected in the field from Indigofera suffruticosa and Pithecellobium sp. The evaluated characteristics were the following: colony characterisation on "79" medium, assimilation of different carbon sources, enzymatic activities, solubilisation of phosphates, nitrogenase activity and antifungal activity against Fusarium oxysporium f. sp. phaseoli. Whole cell protein profiles, 16S rRNA, gyrB, and recA gene sequencing and multilocus sequence typing were used to identify the isolates. The isolates showed different cultural and biochemical characteristics depending on the legume species from which they were obtained. Except for one isolate from I. suffruticosa, all isolates were able to solubilise calcium phosphate and present nitrogenase activity under free-living conditions. Only one isolate from common beans, showed antifungal activity. The forty four isolates from siratro nodules were identified as B. fungorum; isolates UFLA02-27 and UFLA02-28, obtained from common bean plants, were identified as B. contaminans; isolate INPA89A, isolated from Indigofera suffruticosa, was a close relative of B. caribensis but could not be assigned to an established species; isolate INPA42B, isolated from Pithecellobium sp., was identified as B. lata. This is the first report of nitrogenase activity in B. fungorum, B. lata and B. contaminans.
Asunto(s)
Biodiversidad , Burkholderia/clasificación , Burkholderia/metabolismo , Variación Genética , Fijación del Nitrógeno , Plantas/microbiología , Microbiología del Suelo , Proteínas Bacterianas/análisis , Proteínas Bacterianas/genética , Técnicas de Tipificación Bacteriana , Brasil , Burkholderia/genética , Burkholderia/aislamiento & purificación , Análisis por Conglomerados , Girasa de ADN/genética , ADN Bacteriano/química , ADN Bacteriano/genética , ADN Ribosómico/química , ADN Ribosómico/genética , Datos de Secuencia Molecular , Tipificación de Secuencias Multilocus , Filogenia , ARN Ribosómico 16S/genética , Rec A Recombinasas/genética , Rizosfera , Análisis de Secuencia de ADNRESUMEN
The aim of the present study was to identify a collection of 35 Cupriavidus isolates at the species level and to examine their capacity to nodulate and fix N(2). These isolates were previously obtained from the root nodules of two promiscuous trap species, Phaseolus vulgaris and Leucaena leucocephala, inoculated with soil samples collected near Sesbania virgata plants growing in Minas Gerais (Brazil) pastures. Phenotypic and genotypic methods applied for this study were SDS-PAGE of whole-cell proteins, and 16S rRNA and gyrB gene sequencing. To confirm the ability to nodulate and fix N(2), the presence of the nodC and nifH genes was also determined, and an experiment was carried out with two representative isolates in order to authenticate them as legume nodule symbionts. All 35 isolates belonged to the betaproteobacterium Cupriavidus necator, they possessed the nodC and nifH genes, and two representative isolates were able to nodulate five different promiscuous legume species: Mimosa caesalpiniaefolia, L. leucocephala, Macroptilium atropurpureum, P. vulgaris and Vigna unguiculata. This is the first study to demonstrate that C. necator can nodulate legume species.