Bacterial Stress Responses

Abstract

The bacterial stress response is an early-evolved system of protein-folding proteins, both molecular chaperones and protein-folding catalysts, linked to appropriate transcription factors for generating appropriate cellular responses to external and internal stress. Two key requirements of this vital stress response system are robustness and resilience. Most of our understanding of the bacterial stress response comes largely from study of the K12 laboratory strain of E. coli. The essential elements of the cytoplasmic stress response are the protein pairs: chaperonin 60/chaperonin 10 and DnaK/DnaJ whose mechanisms of action are distinct but which work together to maintain cytoplasmic proteostasis. Other cytoplasmic stress proteins include the small heat shock proteins and bacterial Hsp90. The other major cell volume in bacteria is the periplasmic space which, in contrast the cytoplasm, has an oxidising environment. This requires another set of stress proteins including the protein disulphide isomerases and the peptidylprolyl isomerases. Essential to our understanding of the bacterial cell stress response is the realisation that it is a biological control system whose overall role is to enable prokaryotes to cope with any stresses that the environment throws at them – such as the infectious process. It is unclear how the moonlighting actions of certain of these proteins integrates with their protein-folding/stress relieving actions.