Advances in acid-resistant mechanisms and modifications of Escherichia coli

Abstract:

Microbial cells are often subjected to acid stress in natural environments or industrial applications, which severely restricts cell growth and product synthesis efficiency. In order to survive in acidic environments, acid-resistant bacteria have developed diverse protective mechanisms such as hydrogen ion consumption, membrane protection, and metabolic modification to maintain intracellular pH homeostasis. Therefore, in-depth research on acid-resistant mechanisms and improving acid resistance of strains are important for microbial biosynthesis of value-added products. As a model microorganism, Escherichia coli has been well studied regarding the acid-resistant mechanisms. In recent years, significant progress has been achieved in the research on the acid-resistant modification of E. coli. This paper reviews the acid-resistant mechanisms of E. coli in terms of oxidative or glucose-repressed system (acid resistance system 1, AR1), glutamate-dependent acid resistant system (acid resistance system 2, AR2), arginine-dependent acid resistant system (acid resistance system 3, AR3), lysine-dependent acid resistant system (acid resistance system 4, AR4), ornithine-dependent acid resistant system (acid resistance system 5, AR5), cell membrane protection, and biomolecular repair. Furthermore, we summarize the progress in constructing acid-resistant E. coli strains by metabolic engineering, global transcriptional engineering, and adaptive laboratory evolution. Finally, we discuss the subsequent research directions for further deciphering the acid-resistant mechanisms and improving acid resistance of E. coli.