Congresso Brasileiro de Microbiologia 2023

Congresso Brasileiro de Microbiologia 2023

Resumo: 189-1

189-1

POLYPHASIC ANALYSIS OF RHIZOBIA ISOLATED FROM NODULES OF Phaseolus vulgaris L. IN THREE BRAZILIAN BIOMES AND INDICATION OF PUTATIVE NEW SPECIES OF Rhizobium

Autores:

Fernanda Terezinha Moura (UEL - UNIVERSIDADE ESTADUAL DE LONDRINA, EMBRAPA - Empresa Brasileira de Pesquisa Agropecuária) ; Luisa Caroline Ferraz Helene (VITTIA - Vittia Fertilizantes e Biológicos) ; Renan Augusto Ribeiro (EMBRAPA - Empresa Brasileira de Pesquisa Agropecuária) ; Marco Antonio Nogueira (EMBRAPA - Empresa Brasileira de Pesquisa Agropecuária) ; Mariangela Hungria (UEL - UNIVERSIDADE ESTADUAL DE LONDRINA, EMBRAPA - Empresa Brasileira de Pesquisa Agropecuária)

Resumo:

Common bean (Phaseolus vulgaris L.) is a legume of great socioeconomic importance and a main protein source for the population in many countries, including Brazil. An important feature of the legume is its ability to fix atmospheric nitrogen (^N2) in symbiosis with diazotrophic bacteria collectively called “rhizobia”. The symbiosis is characterized by the formation of new organs in the roots, the nodules, where the process of Biological Nitrogen Fixation (BNF) takes place. This study aimed to access the diversity of 13 rhizobia isolated from common bean nodules from seven different municipalities in Mato Grosso do Sul, Brazil, covering three biomes (Cerrado, Pantanal, and Mata Atlântica). A polyphasic approach was used, including phenotypic, genotypic, and phylogenetic analyses. Based on the partial sequences of the 16S rRNA gene, the phylogenetic tree split the strains into two large clades, seven in the Rhizobium etli and six in the Rhizobium tropici. As the 16S rRNA gene is highly conserved and often unable to distinguish closely related species, we proceeded with the Multilocus Sequence Analysis (MLSA) with four concatenated housekeeping genes (glnII, gyrB, recA, and rpoA), which confirmed the phylogenetic position of the strains in the two main clades. The genomes were sequenced, allowing the determination of the parameters of Average Nucleotide Identity (ANI) and digital DNA–DNA hybridization (dDDH). Comparing five strains with the closest Rhizobium species indicated values of ANI and dDDH below the cut-offs for species delineation, ranging from 81.84 to 92.50% and 24.0 to 50.7%, respectively. Phenotypic differences between the strains were also observed, especially in the ability to grow in Luria-Bertani medium, and in YM (Yeast extract-Mannitol) medium with pH 4.0, at 40°C, with 1% NaCl, and in antibiotics intrinsic resistance. Considering the 13 strains, only six were able to reinfect and nodulate the host plant, of which only five showed pink or red internal color. Considering the polyphasic approach, the study pointed out five new putative species, composed one new species of the R. etli clade with two strains, and four new species in the R. tropici clade with six strains, and the remaining five strains being classified as R. phaseoli.

Palavras-chave:

common bean, biological nitrogen fixation, MLSA, nodulation

Agência de fomento:

INCT - Plant Growth Promoting Microorganisms for Agricultural Sustainability and Environmental Responsibility (CNPq 465133/2014-4, Fundação Araucária-STI 043/2019, CAPES)