Genomic analysis of the permafrost isolate Psychrobacter arcticus 273-4 has revealed that a variety of adaptations are employed to enable active growth at subzero temperatures. Many of these low-temperature adaptations are largely similar to adaptations found in other psychrophilic microorganisms isolated from other low-temperature environments and include: changes in amino acid abundance that favor protein mobility; RNA and protein chaperones; and desaturation of membrane lipids. Unlike other psychrophiles, P. arcticus 273-4 constitutively expressed the major cold shock protein (cspA, an RNA chaperone); employed several pairs of isozymes (homologous enzymes with different temperature optima); regulated cell wall elasticity as temperatures decreased; and utilized resources efficiently. These unique low-temperature adaptations may be advantageous in permafrost, where subzero temperatures reign.