The Cold-Shock Response

When a bacterial culture growing exponentially at a temperature optimum for its growth is shifted to low temperature, it exhibits cold-shock response. This is irrespective of the preferred optimum growth temperature; thus all types of bacteria such as psychrotrophic, psychrophilic, mesophilic, and thermophilic bacteria possess cellular machinery to elicit this response. Recent global transcript profiling of Escherichia coli cells undergoing cold shock showed that several genes encoding proteins involved in sugar transport and metabolism were induced by cold shock. Cold-shock response of cold-adapted bacteria is similar to that of mesophiles in aspects such as in many cases a lag phase of growth precedes acclimation to low temperature, specific proteins are induced by temperature downshift, membranes undergo adaptive changes, and enzymes are adapted to function at low temperature. One of the main differences in the cold-shock response of these two types of bacteria is the presence of cold acclimation proteins (Caps) in cold-adapted bacteria. The cold-shock response machinery of cyanobacteria is different from that of E. coli. The two main differences are: (i) the absence of CspA homologs and (ii) the presence of desaturases. Desaturases play an important role in cold-shock response of cyanobacteria. With the advent of DNA microarray technology, several groups have carried out global transcript profiling of cold-shock response of different bacteria. Cellular events occurring during cold-shock response are used in applications such as in food and agricultural industry and in research.