Bacteria respond to an abrupt decrease in temperature with a specific response, in which cold-induced proteins (CIPs) are transiently expressed at a higher level. Employing two-dimensional gel electrophoresis, several CIPs have been identified. In spite of this, the overall function of the cold shock response is unclear. Recently, the main attention has focused on a group of conserved cold shock proteins (CSPs) that have been shown to have the highest induction after cold shock and to play a major regulatory role in the physiology of adaptation to low temperatures. CSPs, of which Escherichia coli, Bacillus subtilis, and B. cereus possess a family comprising at least 3-7 proteins, are small acidic proteins that share over 45% of sequence identity. Recent evidence suggests that members of this wide-spread protein family can function both at the transcriptional and translational level in vitro. However, the exact mode of action has yet to be established. In addition, post-transcriptional regulation seems to play a major role in the induction of CSPs, a process in which the ribosome may be involved. This is in accordance with a model in which the ribosome has been proposed to be the sensor of temperature in bacteria.
