Exposure to low temperatures induces the biosynthesis of specific sets of proteins, including cold shock proteins (Csps). Since many of the specific functions of pychrophilic Csps are unknown, the roles of Csps from an Arctic bacterium, Polaribacter irgensii KOPRI 22228, were examined. The genes encoding CspA and CspC of P. irgensii were cloned in this study. Sequence analysis showed that these proteins have cold shock domains containing two RNA-binding motifs, RNP1 and RNP2. Both proteins bound oligo(dT)-cellulose resins, suggesting single-stranded nucleic acid-binding activity. When the P. irgensii Csps were overexpressed in Escherichia coli, the cold-resistance of the host was increased by more than five-fold. The P. irgensii Csps also rescued a cold-sensitive E. coli csp-quadruple deletion strain, BX04, at low temperatures. These results suggest that Csps from P. irgensii play a role in survival in polar environments.