Proteomic analysis of Psychrobacter cryohalolentis K5 during growth at subzero temperatures.

It is crucial to examine the physiological processes of psychrophiles at temperatures below 4 degrees C, particularly to facilitate extrapolation of laboratory results to in situ activity. Using two dimensional electrophoresis, we examined patterns of protein abundance during growth at 16, 4, and -4 degrees C of the eurypsychrophile Psychrobacter cryohalolentis K5 and report the first identification of cold inducible proteins (CIPs) present during growth at subzero temperatures. Growth temperature substantially reprogrammed the proteome; the relative abundance of 303 of the 618 protein spots detected (approximately 31% of the proteins at each growth temperature) varied significantly with temperature. Five CIPs were detected specifically at -4 degrees C; their identities (AtpF, EF-Ts, TolC, Pcryo_1988, and FecA) suggested specific stress on energy production, protein synthesis, and transport during growth at subzero temperatures. The need for continual relief of low-temperature stress on these cellular processes was confirmed via identification of 22 additional CIPs whose abundance increased during growth at -4 degrees C (relative to higher temperatures). Our data suggested that iron may be limiting during growth at subzero temperatures and that a cold-adapted allele was employed at -4 degrees C for transport of iron. In summary, these data suggest that low-temperature stresses continue to intensify as growth temperatures decrease to -4 degrees C.