Abstract:Proper pH is crucial for the survival and functions of microorganisms, whether in the environment or within cells. Under acidic or alkaline stress, microorganisms have evolved diverse strategies, such as proton transport, production of acidic or alkaline substances, and cell membrane protection, to maintain intracellular pH homeostasis. Moreover, microorganisms have evolved the ability to actively change the extracellular pH. This article reviews the mechanisms by which microorganisms maintain intracellular pH homeostasis under acid or alkaline stress and alter extracellular pH. It aims to enhance our understanding of the interaction between microorganisms and the environment and provide a reference for further research on the synergistic mechanisms between microorganisms and the environment.