Differential induction of heat shock, SOS, and oxidation stress regulons and accumulation of nucleotides in Escherichia coli

Abstract

Heat and various inhibitory chemicals were tested in Escherichia coli for the ability to cause accumulation of adenylylated nucleotides and to induce proteins of the heat shock (htpR-controlled), the oxidation stress (oxyR-controlled), and the SOS (lexA-controlled) regulons. Under the conditions used, heat and ethanol initiated solely a heat shock response, hydrogen peroxide and 6-amino-7-chloro-5,8-dioxoquinoline (ACDQ) induced primarily an oxidation stress response and secondarily an SOS response, nalidixic acid and puromycin induced primarily an SOS and secondarily a heat shock response, isoleucine restriction induced a poor heat shock response, and CdCl2 strongly induced all three stress responses. ACDQ, CdCl2, and H2O2 each stimulated the synthesis of approximately 35 proteins by factors of 5- to 50-fold, and the heat shock, oxidation stress, and SOS regulons constituted a minor fraction of the overall cellular response. The pattern of accumulation of adenylylated nucleotides during these treatments was inconsistent with a simple role for these nucleotides as alarmones sufficient for triggering the heat shock response, but was consistent with a role in the oxyR-mediated response.