Rhodoglobus galactosidasius sp. nov., a psychrophilic Actinomycetota producing a cold-active β-galactosidase isolated from Cape Hallett, Antarctica

Abstract

A novel psychrophilic member of the phylum Actinomycetota , designated strain CPHL_1 T , was isolated from the shoreline of Cape Hallett, Antarctica. Cells were Gram-positive, aerobic, non-motile, non-spore-forming rods (0.7–1.0 µm in length) with orange to yellow pigmentation. Optimal growth occurred at 15 °C, pH 8.0, with NaCl tolerance up to 3% (w/v). Strain CPHL_1 T exhibited cytosolic cold-active β-galactosidase activity, with an optimum at 15 °C and pH 7.0 and formed non-adherent biofilms. Phylogenetic analysis based on 16S rRNA gene sequence placed the strain within the genus Rhodoglobus , showing high similarity to Rhodoglobus vestalii LV3 T (99.4%) and Rhodoglobus aureus CMS 81y T (97.6%). Chemotaxonomic characteristics, including the predominance of anteiso-C 15 : 0 , anteiso-C 17 : 0 and iso-C 16 : 0 fatty acids, the presence of MK-11, MK-10 and MK-12 as the major respiratory quinones, and genomic G+C content of 60%, further supported its assignment to the genus Rhodoglobus . Whole-genome comparisons revealed clear taxonomic distinction, with strain CPHL_1 T sharing 88.9% average nucleotide identity (ANI) and 38.3% digital DNA–DNA hybridization (dDDH) values with R. aureus , and 81.7% ANI and 25.1% dDDH with R. vestalii , confirming its status as a novel species. Phylogenetic analysis revealed that the β-galactosidases from these Rhodoglobus strains form a well-supported clade with high sequence similarity. Based on these data, a novel species is proposed: Rhodoglobus galactosidasius sp. nov. (type strain CPHL_1 T =ITEM 19986 T =KCTC 59592 T ). Genomic analyses also highlighted its biosynthetic potential for specialized metabolites, consistent with the recognized metabolic diversity of the genus.

The authors' abstract, as published at the source. INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY, 2026 · DOI ↗