We report in this study the first genome sequencing, profiling and characterization of a bacterial strain from the Psychrobacter genus, isolated from the 5,000-year-old ice layer in the Scarisoara Ice Cave.

This Psychrobacter strain showed a multidrug-resistance phenotype and significant antimicrobial activity, which was further correlated with clinically important resistance genes. The strain is a polyextremophile, showing both psychrophilic and moderate halophilic characteristics. Phylogenetic analysis placed the Scarisoara strain close to other psychrophilic Psychrobacter species. Functional assays revealed specific enzymatic activity, and a multi-drug resistance phenotype. The genome contains over 100 genes associated with antimicrobial resistance, some of them of clinical and epidemiological importance. This bacterium exhibited antimicrobial activity against several clinically isolated pathogens, both Gram-negative and Gram-positive pathogens, which could be correlated with the presence of genes encoding for antimicrobial compounds such as glycopeptides and bacitracin.

Based on its functional and genomic profile, the Psychrobacter strain from the five-millennia-old ice layer of the Scarisoara Ice Cave glacier can be regarded as an ancient, ice-adapted polyextremophile with significant potential for novel ecological, biotechnological and medical applications. To the best of our knowledge, this study provides the first genome analysis of a Psychrobacter species isolated from an ice cave, as well as the first characterization of ancient resistomes within this largely unexplored environment.