Pseudofrankia coriaricola sp. nov., isolated from root nodules of Coriaria myrtifolia

Strains BMG5.36ᵀ and BMG5.37, two filamentous actinobacteria, were isolated from root nodules of Coriaria myrtifolia collected in Algeria and subjected to a polyphasic taxonomic analysis to determine their position within the family Frankiaceae . The strains formed branched, septate hyphae bearing sporangium-like structures. Chemotaxonomic characteristics, including a fatty acid profile dominated by iso-C _16:0 , C _17:1 ω 8c and C _15:0 , as well as cell-wall sugars and phospholipid composition, were consistent with assignment to the genus Pseudofrankia . Phylogenetic and phylogenomic analyses based on 16S rRNA gene sequences and 120 conserved single-copy proteins placed the strains in a distinct and well-supported lineage within Pseudofrankia , clearly separated from members of Frankia , Protofrankia and Parafrankia . Digital DNA–DNA hybridization (dDDH) and average nucleotide identity (ANI) values showed that the two strains represent a single genomic species (95.9% dDDH; >99.9% ANI) and are distinct from all described species (dDDH <70%; ANI <95%), with the highest relatedness of 41.6% dDDH and 91.1% ANI. Pan-genome analysis revealed an open genome with a reduced core and a large accessory fraction, including shared accessory gene clusters supporting their genomic coherence and differentiation. Genome mining indicated metabolic versatility and traits consistent with ecological specialization. Phenotypic features, including tolerance to NaCl, substrate utilization and antibiotic susceptibility patterns, further distinguished the strains from related taxa. On the basis of the combined genotypic and phenotypic evidence, strains BMG5.36ᵀ (=DSM 105291ᵀ=CECT 9310ᵀ) and BMG5.37 (=DSM 110006=CECT 9311) are considered to represent a novel species of the genus Pseudofrankia , for which the name Pseudofrankia coriaricola sp. nov. is proposed.