Impairment of Ribosome Maturation or Function Confers Salt Resistance on Escherichia coli Cells

We found that loss of integrity of the ribosome by removal of a putative ribosome maturation factor or a ribosomal protein conferred salt tolerance on Escherichia coli cells. Some protein synthesis inhibitors including kasugamycin and chloramphenicol also had a similar effect, although kasugamycin affected neither 16S rRNA maturation nor subunit association into a 70S ribosome. Thus, salt tolerance is a common feature of cells in which maturation or function of the ribosome is impaired. In these cells, premature induction of an alternative sigma factor, σE, by salt stress was observed. These results suggest the existence of a yet-unknown stress response pathway mediated by the bacterial ribosome.