Abstract
The extreme conditions of the Antarctic environment have driven the evolution of highly specialized microbial communities with unique adaptations. In this study, we characterized five Pseudomonas isolates from James Ross Island, which displayed notable taxonomic and metabolite features. Phylogenomic analysis revealed that strain P2663(T) occupies a distinct phylogenetic position within the Pseudomonas genus, related to species Pseudomonas svalbardensis, Pseudomonas silesiensis, Pseudomonas mucoides, Pseudomonas prosekii, and Pseudomonas gregormendelii. The novelty of five Antarctic isolates was further confirmed through analyses of housekeeping genes, ribotyping, and REP-PCR profiling. MALDI-TOF MS analysis identified 11 unique mass spectrometry signals shared by the Antarctic isolates, which were not detected in other related species. Additionally, chemotaxonomic characterization, including fatty acid composition, demonstrated similarities with related Pseudomonas species. Phenotypic assessments revealed distinctive biochemical and physiological traits. In-depth genomic analysis of strain P2663(T) uncovered numerous genes which could be involved in survival in extreme Antarctic conditions, including those encoding cold-shock and heat-shock proteins, oxidative and osmotic stress response proteins, and carotenoid-like pigments. Genome mining further revealed several biosynthetic gene clusters, some of which are associated with antimicrobial activity. Functional assays supported the antimicrobial capabilities of this novel species, showing antagonistic effects against clinical isolates of Pseudomonas aeruginosa, possibly mediated by tailocins (phage tail-like particles). This comprehensive polyphasic study characterized a new cold-adapted species, for which we propose the name Pseudomonas rossensis sp. nov.