We have characterized genetic, phenotypic and symbiotic properties of bacterial strains previously isolated from nitrogen-fixing nodules of Retama sphaerocarpa from Northern Algeria. Phylogenetic analyses of 16S rRNA genes and three concatenated housekeeping genes, recA, atpD and glnII, placed them in a new divergent group that is proposed to form a new Bradyrhizobium species, Bradyrhizobium algeriense sp. nov. (type strain RST89T, LMG 27618 and CECT 8363). Based on these phylogenetic markers and on genomic identity data derived from draft genomic sequences, Bradyrhizobium valentinum LmjM3T, Bradyrhizobium lablabi CCBAU 23086T, Bradyrhizobium retamae Ro19T, and Bradyrhizobium jicamae PAC68T are the closest relatives of B. algeriense RST89T, with sequence identities of 92–94% and Average Nucleotide Identities (ANIm) under 90%, well below the 95–96% species circumscription threshold. Likewise, a comparison of whole-cell proteomic patterns, estimated by Matrix-Assisted Laser Desorption/Ionization-Time-of-Flight (MALDI-TOF) mass spectrometric analysis, yielded almost identical spectra between B. algeriense strains but significant differences with B. valentinum, Bradyrhizobium paxllaeri, Bradyrhizobium icense, B. lablabi, B. jicamae and B. retamae. A phylogenetic tree based on symbiotic gene nodC revealed that the B. algeriense sequences cluster with sequences from the Bradyrhizobium symbiovar retamae, previously defined with B. retamae strains isolated from Retama monosperma. B. algeriense strains were able to establish effective symbioses with Retama raetam, Lupinus micranthus, Lupinus albus and Genista numidica, but not with Lupinus angustifolius or Glycine max.
