Azospirillum sp. strain Sp245T, originally identified as belonging to Azospirillum brasilense , is recognized as a plant-growth-promoting rhizobacterium due to its ability to fix atmospheric nitrogen and to produce plant-beneficial compounds. Azospirillum sp. Sp245T and other related strains were isolated from the root surfaces of different plants in Brazil. Cells are Gram-negative, curved or slightly curved rods, and motile with polar and lateral flagella. Their growth temperature varies between 20 to 38 °C and their carbon source utilization is similar to other Azospirillum species. A preliminary 16S rRNA sequence analysis showed that the new species is closely related to A. brasilense Sp7T and A. formosense CC-Nfb-7T. Housekeeping genes revealed that Azospirillum sp. Sp245T, BR 12001 and Vi22 form a separate cluster from strain A. formosense CC-Nfb-7T, and a group of strains closely related to A. brasilense Sp7T. Overall genome relatedness index (OGRI) analyses estimated based on average nucleotide identity (ANI) and digital DNA–DNA hybridization (dDDH) between Azospirillum sp. Sp245T and its close relatives to other Azospirillum species type strains, such as A. brasilense Sp7T and A. formosense CC-Nfb-7T , revealed values lower than the limit of species circumscription. Moreover, core-proteome phylogeny including 1079 common shared proteins showed the independent clusterization of A. brasilense Sp7T, A. formosense CC-Nfb-7T and Azospirillum sp. Sp245T, a finding that was corroborated by the genome clustering of OGRI values and housekeeping phylogenies. The DNA G+C content of the cluster of Sp245T was 68.4–68.6 %. Based on the phylogenetic, genomic, phenotypical and physiological analysis, we propose that strain Sp245T together with the strains Vi22 and BR12001 represent a novel species of the genus Azospirillum , for which the name Azospirillum baldaniorum sp. nov. is proposed. The type strain is Sp245T (=BR 11005T=IBPPM 219T) (GCF_007827915.1, GCF_000237365.1, and GCF_003119195.2).

Strain Az39T of Azospirillum is a diazotrophic plant growth-promoting bacterium isolated in 1982 from the roots of wheat plants growing in Marcos Juárez, Córdoba, Argentina. It produces indole-3-acetic acid in the presence of l-tryptophan as a precursor, grows at 20–38 °C (optimal 38 °C), and the cells are curved or spiral-shaped, with diameters ranging from 0.5–0.9 to 1.8–2.2 µm. They contain C16 : 0, C18 : 0 and C18 : 1  ω7c/ω6c as the main fatty acids. Phylogenetic analysis of its 16S rRNA gene sequence confirmed that this strain belongs to the genus Azospirillum , showing a close relationship with Azospirillum baldaniorum Sp245T, Azospirillum brasilense Sp7T and Azospirillum formosense CC-Nfb-7T. Housekeeping gene analysis revealed that Az39T, together with five strains of the genus (Az19, REC3, BR 11975, MTCC4035 and MTCC4036), form a cluster apart from A. baldaniorum Sp245T, A. brasilense Sp7T and A. formosense CC-Nfb-7T. Average nucleotide identity (ANI) and digital DNA–DNA hybridization (dDDH) between Az39T and the aforementioned type strains revealed values below 96 %, the circumscription limit for the species delineation (ANI: 95.3, 94.1 and 94.0 %; dDDH: 62.9, 56.3 and 55.6 %). Furthermore, a phylogeny evaluation of the core proteome, including 809 common shared proteins, showed an independent grouping of Az39T, Az19, REC3, BR 11975, MTCC4035 and MTCC4036. The G+C content in the genomic DNA of these six strains varied from 68.3 to 68.5 %. Based on the combined phylogenetic, genomic and phenotypic characterization presented here, we consider that strain Az39T, along with strains Az19, REC3, BR 11975, MTCC4035 and MTCC4036, are members of a new Azospirillum species, for which the name Azospirillum argentinense sp. nov. is proposed. The type strain is Az39T (=LBPCV39T=BR 148428T=CCCT 22.01T).

O metabolismo de nitrogênio em plantas de arroz é severamente afetado pela deficiência de cálcio e magnésio Nitrogen metabolism in rice plants is severely affected by calcium and magnesium deficiency

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