Bacterial adaptation to low temperature: Implications for cold-inducible genes

A subset of proteins, termed cold-shock proteins, is transiently synthesize d when bacterial cells are abruptly exposed to a low temperature. This phen omenon was originally found in Escherichia coli and later found to be a col d-shock response common to many bacterial species. CspA of 7.4 kD, a major cold-shock protein in E. coli, has been shown to share structural similarit y with a class of eukaryotic Y box proteins which have RNA-binding domains. Transient synthesis of CspA upon cold shock is mediated by increased stabi lization of the mRNA at low temperatures. The proposed role of some cold-sh ock proteins including CspA in the bacterial adaptation to low temperatures is to function as a RNA chaperone in the regulation of translation. Some e nzymes of psychrotrophic or psychrophilic bacteria exhibit unique features of a cold-adapted enzyme, high catalytic activity at a low temperature and rapid inactivation at a moderate temperature A monomeric isocitrate dehydro genase isozyme (IDH-II) of a psychrophilic bacterium, Vibrio sp, strain ABE -1, is a typical cold-adapted enzyme. In addition, this enzyme is induced a t low temperatures. Low temperature-dependent expression of icdII encoding IDH-II is controlled by two different cis-elements located at the untransla ted upstream region of the gene, one is a silencer and the other is essenti al for the low temperature response. The physiological role of IDH-II is ev aluated by transforming E. coli with icdII, The growth rate of the E:coli t ransformants at low temperatures is dependent on the level of expressed IDH -II activity.