Genomic and physiological analysis of C carotenoid-producing novel Halorubrum ruber sp. nov.

A novel haloarchaeal species designated as MBLA0099 was isolated from seawater near Yeongheung Island. Cells were Gram-negative, non-motile, red-pigmented, and rod-shaped. They grew at 10-45°C, within pH 5.5-9.0, and between 7.5% and 30% NaCl concentrations. Cells were able to grow without Mg and were lysed in distilled water. The size of the whole-genome and G + C content of DNA was 3.02 Mb and 68.9 mol%, respectively. Phylogenetic analysis shows that the strain MBLA0099 belongs to the genus Halorubrum. The average nucleotide and amino acid identity, and in silico DNA-DNA hybridization values were below the species delineation threshold. Pan-genomic analysis revealed that 3.2% of all genes present in strain MBLA0099 were unique to the strain. The red carotenoid produced by strain MBLA0099 was subjected to spectrometric and chromatographic analyses and confirmed to be bacterioruberin as C50 carotenoid. Mevalonic acid, terpenoid backbone, and carotenoid biosynthesis pathway were annotated for strain MBLA0099. The C50 carotenoid production by strain MBLA0099 was also enhanced under various stress conditions including relatively netural pH, high oxidative and salinity conditions. Additionally, the strain MBLA0099-derived bacterioruberin showed the antioxidant activity with EC value of 12.29 µg/ml, based on the evaluation of DPPH free radical scavenging activity. The present study would be the first report on the identification of C carotenoid from the strain MBLA0099 representing a novel species of the genus Halorubrum, for which the name Halorubrum ruber sp. nov. is proposed. The typestrain used was MBLA0099 (= KCTC 4296 = JCM 34701).