Importance of glutathione for growth and survival of Escherichia coli cells: detoxification of methylglyoxal and maintenance of intracellular K+.

The role of the tripeptide glutathione in the growth and survival of Escherichia coli cells has been investigated. Glutathione-deficient mutants leak potassium and have a reduced cytoplasmic pH. These mutants are more sensitive to methylglyoxal than the parent strain, indicating that in the absence of glutathione-dependent detoxification, acidification of the cytoplasm cannot fully protect cells. However, increasing the intracellular pH of the glutathione-deficient strain resulted in enhanced sensitivity to methylglyoxal. This suggests that acidification of the cytoplasm can provide some protection to E. coli cells in the absence of glutathione. In the presence of the Kdp system, glutathione-deficient mutants are highly sensitive to methylglyoxal. This is due to the higher intracellular pH in these cells. In the absence of methylglyoxal, the presence of the Kdp system in a glutathione-deficient strain also leads to an extended lag upon dilution into fresh medium. These data highlight the importance of glutathione for the regulation of the K+ pool and survival of exposure to methylglyoxal.