Identification of phenotypic and genotypic properties and cold adaptive mechanisms of novel freeze–thaw stress-resistant strain Pseudomonas mandelii from Antarctica

Antarctica is a region with harsh conditions which have become a focus of research for identifying novel extreme microorganisms in recent years. Here, we identified and characterized the KGI_MA19 isolate obtained by enriched culture and freeze–thaw stress treatment from the sediment samples of King George Island in Antarctica. Whole-genome sequencing, MLSA, and phylogenetic analyses revealed that this isolate was a novel strain of Pseudomonas mandelii sharing less similarity to the first Pseudomonas mandelii isolate 6A1 from Antarctica. The phenotypic and biochemical characterizations indicate that this psychrotolerant and halotolerant strain can use disaccharides as a carbon source, has denitrification ability, and has multiple antibiotic resistance. Moreover, comparative proteomic analyses showed that P. mandelii KGI_MA19 adapts to the cold environment by changing its membrane composition, excreting EPS, and producing major cold shock proteins, in addition to turning off its other stress response mechanisms.