Autotransporter BrkA and Chaperone Protein DegP may be Required for Escherichia coli Survival at Elevated Temperatures

Abstract

Autotransporters, a class of virulence-associated proteins in the outer membrane of Gram-negative bacteria, are capable of independent secretion and often contribute to pathogenicity. Bordetella pertussis, the causative agent of whooping cough, expresses the 103 kDa type Va autotransporter Bordetella resistance to killing (BrkA), a virulence factor that helps the bacterium resist complement-mediated killing. DegP is a chaperone that acts as a temperature-dependent serine protease and plays a critical role in degrading misfolded periplasmic proteins and maintaining protein homeostasis under environmental stress, particularly elevated temperatures. While DegP has been implicated in autotransporter folding and secretion in Escherichia coli, its role in BrkA expression and function remains uncharacterized. In this study, we assessed the heat-stress response in E. coli by measuring optical density after overnight growth to evaluate survival of wild-type and ∆degP mutant strains at 37°C and 42°C in the context of BrkA expression. Optical density measurements revealed that ∆degP strains failed to grow at 42°C regardless of BrkA expression, validating previous work on DegP’s role in heat tolerance. Interestingly, wild-type E. coli strains also failed to grow at 42°C, but this phenotype was rescued by BrkA expression. This suggests a novel protective role for BrkA during heat stress that may be DegP-dependent. These findings reaffirm DegP’s importance in thermal stress response and highlight interactions between periplasmic chaperones and autotransporters during environmental stress. This study provides insight on the roles of DegP and BrkA in bacterial viability during elevated temperatures, offering new avenues for investigating stress mechanisms and potential targets for modulating bacterial survival.