Identificação e filogenia de rizóbios simbióticos de espécies florestais

Abstract

Brazil is known for its great plant diversity and biotechnological potential. The rhizobium-legume symbiosis is an important source of fixed nitrogen (ammonia) in the biosphere and the identification of rhizobia that promote better fixation in their host is a very valuable area of knowledge to generate alternatives to mineral nitrogen fertilizers. Several new species of symbiotic nitrogen-fixing bacteria have already been described, mainly belonging to the genera Bradyrhizobium and Rhizobium. However, there is no identification at the species level of strains that nodulate and fix N2 in symbiosis with the native forest legume Machaerium nyctitans (Vell.) Benth. and Platypodium elegans (Voegel.). The aim of this work was to genetically and phenotypically characterize strains isolated from forest species (Machaerium nyctitans and Platypodium elegans) with noduliferous and atmospheric nitrogen fixing capacities. In addition, new species of the genera Bradyrhizobium and Rhizobium were presented, among them. For this purpose, DNA extraction of strains UFLA01-814, UFLA01-839, UFLA01-860, UFLA01-1127, UFLA01-1134 and UFLA01-1164 was performed for subsequent genome sequencing of each one. The genomic analysis included the comparison of the genome of the study strains with genomes of the Bradyrhizbium and Rhizobium genera available at the NCBI (National Center for Biotechnology Information) by ANI (average nucleotide identity) and TYGS (Type genome server). From the evidence found and the entire characterization of the strains, it is possible to prove the existence of four new species of rhizobia, three of the genus Bradyrhizobium and one of the genus Rhizobium.