Abstract
Zooplankton in the Southern Ocean represent unique microhabitats for microbial communities that contribute significantly to polar biogeochemical cycles. In this study, we performed a polyphasic and genomic characterization of two Gram-negative, psychrotolerant bacterial strains, HL-MZ7T and HL-MZ19, isolated from Antarctic zooplankton. Phylogenetic and phylogenomic analyses clearly placed these isolates within the genus Pseudocolwellia, forming a sister clade to Pseudocolwellia agarivorans QM50T. The complete genomes of HL-MZ7T (4.5 Mbp) and HL-MZ19 (4.6 Mbp) exhibited DNA G + C contents of 36.0% and 35.9%, respectively. Average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values confirmed that both strains represent a novel genomic species, distinct from P. agarivorans QM50T (79.5% ANI and 24.0% dDDH). Comparative genomic analysis revealed a rich repertoire of genes associated with cold environmental adaptation and host-microbe interactions. Notably, we identified biosynthetic gene clusters of aryl polyenes and homoserine lactones, alongside genes involved in surface adhesion and nutrient acquisition, suggesting a specialized symbiotic potential within the zooplankton micro-niche. Phenotypically, the strains are characterized as strictly aerobic, with optimal growth at 15–20 °C and 3.0% (w/v) sea salts. These findings expand the genomic and ecological understanding of zooplankton-associated bacteria in polar marine ecosystems, and support the proposal of Pseudocolwellia antarctica sp. nov.
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Funding
This research was supported by the Global-LAMP Program of the National Research Foundation of Korea (NRF) grant funded by the Ministry of Education (RS-2023-00301976); NRF grant funded by the Korea government (Ministry of Science and ICT) (RS-2024-00405801); Korea Institute of Marine Science & Technology Promotion (KIMST) grant funded by the Ministry of Oceans and Fisheries (RS-2024-00436649).
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Kim, M.K., Oh, S.J., Lee, B.M. et al. Genomic and phenotypic insights into Pseudocolwellia antarctica sp. nov., a novel psychrotolerant bacterium with symbiotic potential from Antarctic zooplankton.
Sci Rep (2026). https://doi.org/10.1038/s41598-026-53601-5
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DOI: https://doi.org/10.1038/s41598-026-53601-5
Keywords
Pseudocolwellia antarctica
- Southern Ocean
- Zooplankton
- Symbiosis
- Cold adaptation
Source: Ecology - nature.com
