Pseudorhizobium pelagicum gen. nov., sp. nov. isolated from a pelagic Mediterranean zone

Two novel Alphaproteobacteria strains, R1-200B4T and R2-400B4, were isolated from the Mediterranean Sea off the coast of Alicante in Spain. The phylogenetic analysis of the 16S rRNA gene showed that they are related to members of Family Rhizobiaceae. The 16S rRNA gene sequence of strain R1-200B4T presents 97.0% and 95.6% similarity with respect to the type strains of the type species from genera Neorhizobium and Rhizobium, Neorhizobium galegae HAMBI 540T and Rhizobium leguminosarum USDA 2370T, respectively. The remaining genera of family Rhizobiaceae showed similarities lower than 95%. The recA and atpD gene sequences of strain R1-200B4T showed, respectively, 90% and 88.6% similarity with respect to N. galegae HAMBI 540T and 87% and 86% with respect to R. leguminosarum USDA 2370T. The calculated ANI values between the genomes of the strain R1-200B4T and those of N. galegae HAMBI 540T and R. leguminosarum 3841 are 75.9% and 74.0%, respectively. The major fatty acids are those from summed feature 8 (C18:1 ω6c/C18:1 ω7c) and the C16:0. Catalase and oxidase were positive. Nitrate reduction and aesculin hydrolysis were positive. Production of β-galactosidase and urease was positive. The production of indol, arginine dehydrolase or gelatinase was negative. Growth was observed in presence of 7% NaCl. Therefore, based on the phylogenetic, chemotaxonomic and phenotypic data obtained in this study, we propose to classify the strains isolated in this study in a new genus named Pseudorhizobium gen. nov. and a new species named Pseudorhizobium pelagicum sp. nov. with the type strain R1-200B4T (= LMG 28314T = CECT 8629T).