Rhizobium croatiense sp. nov. and Rhizobium redzepovicii sp. nov., two new species isolated from nodules of Phaseolus vulgaris in Croatia

Phaseolus vulgaris is a legume indigenous to America which is nodulated by strains of genus Rhizobium in Croatia. Four of these strains, 13T(T), 9(T), 18T(T) and 8Z are phylogenetically close to the species from the Rhizobium leguminosarum phylogenetic complex in the 16S rRNA gene analysis. The results of both the analyses of the concatenated recA and atpD genes and whole genomes revealed that the strains 13T(T) and 9(T) clustered with Rhizobium sophoriradicis CCBAU 03470(T) and the strains 18T(T) and 8Z with Rhizobium ecuadorense CNPSO 671(T). Whole genome average nucleotide identity blast (ANIb) and dDDH values between the strains 13T(T) and the type strain of R. sophoriradicis and between the strains 18T(T) and the type strain of R. ecuadorense were lower than 95% and 70%, respectively, which are the threshold values recommended for bacterial species differentiation. These results combined with those of chemotaxonomic and phenotypic analyses support the affiliation of these strains to two novel species within the genus Rhizobium for which we propose the names Rhizobium croatiense sp. nov. 13T(T) (=LMG 32397(T), = HAMBI 3740(T)) as type strain and Rhizobium redzepovicii sp. nov. 18T(T) (=LMG 32398(T), = HAMBI 3741(T)) as type strain. (C) 2022 The Author(s). Published by Elsevier GmbH.

Automated summary

This study identified a symbiotic relationship between nodulated legume and strains of genus Rhizobium in Croatia. The analysis revealed that these strains are closely related to species from the Rhizobium leguminosarum phylogenetic complex. Based on genetic and phenotypic analyses, two novel species within the genus Rhizobium were proposed and named Rhizobium croatiense and Rhizobium redzepovicii.