Genome analysis of Hyunsoonleella sp. J2K-J805 reveals putative genes associated with zeaxanthin biosynthesis.

Hyunsoonleella sp. strain J2K-J805 is a yellow-pigmented marine bacterium isolated from coastal seawater collected at Jongdal-ri, Jeju Island, Republic of Korea. Here, we report the single-contig genome sequence of strain J2K-J805 obtained using Oxford Nanopore sequencing and de novo assembly. The genome is 3,825,400 bp long with a DNA G + C content of 34.9 mol%, 100% breadth of coverage, a mean depth of 50×, 99.98% completeness, and 0.01% contamination. Annotation predicted 3285 coding sequences, 37 tRNAs, 6 rRNAs, 24 ncRNAs, 16 pseudogenes, and 3 CRISPR arrays. Whole-genome comparisons indicated that strain J2K-J805 is most closely related to Hyunsoonleella flava T58T (OrthoANIu 87.72%; dDDH 34.5%), with values below the species-delineation thresholds. Screening of public metagenomes recovered J2K-J805-associated k-mers mainly from marine, aquatic, and sediment datasets, whereas no species representative in the screened GTDB collection met the species-level cutoff. The genome encoded a co-localized cluster of carotenoid biosynthesis genes (crtI, crtB, crtZ, and crtY), the IPP isomerase gene idi, and a near-complete mevalonate (MVA) pathway, consistent with a putative pathway for zeaxanthin biosynthesis. This genome expands the genomic resources available for the genus Hyunsoonleella and provides a foundation for comparative studies of carotenoid biosynthesis in marine Flavobacteriaceae.