capA, a cspA-like gene that encodes a cold acclimation protein in the psychrotrophic bacterium Arthrobacter globiformis SI55

By use of Arthrobacter globiformis SI55, a psychrotrophic bacterium capable of growth between -5 and +32 degrees C, we cloned and sequenced capA, a gene homologous to cspA encoding the major cold shock protein in Escherichia coli. The deduced protein sequence has a high level of identity with the sequences of other CspA-related proteins from various sources, and no particular residue or domain that could be specific to cold-adapted microorganisms emerged. We show that CapA was produced very rapidly following cold shock, but unlike its mesophilic counterparts, it was still expressed during prolonged growth at low temperature. Its synthesis is regulated at the translational level, and we showed that growth resumption following a temperature downshift correlated with CapA expression. Transient inhibitions in protein synthesis during the first stages of the cold shock response severely impaired the subsequent acclimation of A. globiformis SI55 to low temperature and delayed CapA expression. The cold shock response in A. globiformis SI55 is an adaptative process in which CapA may play a crucial role. We suggest that low-temperature acclimation is conditioned mainly by the ability of cells to restore an active translational machinery after cold shock in a process that may be different from that present in mesophiles.