Trehalose synthesis is induced upon exposure of Escherichia coli to cold and is essential for viability at low temperatures

Trehalose accumulates dramatically in microorganisms during heat shock and osmotic stress and helps protect cells against thermal injury and oxygen radicals. Here we demonstrate an important role of this sugar in cold-adaptation of bacteria. A mutant Escherichia coli strain unable to produce trehalose died much faster than the wild type at 4degreesC. Transformation of the mutant with the otsA/otsB genes, responsible for trehalose synthesis, restored trehalose content and cell viability at 4degreesC. After temperature downshift from 37degreesC to 16degreesC ("cold shock"), trehalose levels in wild-type cells increased up to 8-fold. Although this accumulation of trehalose did not influence growth at WC, it enhanced cell viability when the temperature fell further to 4degreesC. Before the trehalose build-up, levels of mRNA encoding OtsA/OtsB increased markedly. This induction required the or factor, RpoS, but was independent of the major cold-shock protein, CspA. otsA/B mRNA was much more stable at 16degreesC than at 37degreesC and contained a "downstream box" characteristic of cold-inducible mRNAs. Thus, otsA/otsB induction and trehalose synthesis are activated during cold shock (as well as during heat shock) and play an important role in resistance of E. coli (and probably other organisms) to low temperatures.