Abstract
Two novel Gram-stain-negative, strictly aerobic, halophilic and non-motile bacterial strains, designated NKW23(T) and NKW57(T), were isolated from a brittle star Ophioplocus japonicus collected from a tidal pool in Wakayama, Japan. The results of phylogenetic analysis based on 16S rRNA gene sequences indicated that NKW23(T) represented a member of the family Paracoccaceae, with Limibaculum halophilum CAU 1123(T) as its closest relative (94.4% sequence identity). NKW57(T) was identified as representing a member of the family Microbulbiferaceae, with up to 94.9% sequence identity with its closest relatives. Both strains displayed average nucleotide identity (ANI) and digital DNA-DNA hybridisation (dDDH) values below the species delimitation threshold against their closest relatives. Additionally, amino acid identity (AAI) values of both strains fell below the genus-defining threshold. Phylogenetic trees based on genome sequences indicated that NKW23(T) formed a novel lineage, branching deeply prior to the divergence of the genera Limibaculum and Thermohalobaculum, with an evolutionary distance (ED) of 0.31-0.32, indicative of genus-level differentiation. NKW57(T) similarly formed a distinct lineage separate from the species of the genus Microbulbifer. The major respiratory quinones of NKW23(T) and NKW57(T) were ubiquinone-10 (Q-10) and Q-8, respectively. The genomic DNA G+C contents of NKW23(T) and NKW57(T) were 71.4 and 58.8%, respectively. On the basis of the physiological and phylogenetic characteristics, it was proposed that these strains should be classified as novel species representing two novel genera: Paralimibaculum aggregatum gen. nov., sp. nov., with strain NKW23(T) (=JCM 36220(T)=KCTC 8062(T)) as the type strain, and Biformimicrobium ophioploci gen. nov., sp. nov., with strain NKW57(T) (=JCM 36221(T)=KCTC 8063(T)) as the type strain.