Adaptive defensive mechanism of bioleaching microorganisms under extremely environmental acid stress: Advances and perspectives

Bioleaching microorganisms inhabit extremely acidic environments (pH < 3.0) and can be used in the biohydrometallurgical industry. They employ several strategies, such as biofilms formation, mechanical defense, membrane reversal potential, proton efflux, intracellular buffering, and protection, or repair mechanism of biomacromolecules, to maintain their intracellular pH within a narrow range, which is close to neutral, for conducting normal physiological activity. In this review, we describe the effects of these strategies on the homeostasis of intracellular pH of bioleaching microorganisms and the relevant energy metabolism. The potential significance of horizontal gene transfer and gene loss in their adaptation to the environment, and the prospect of new technologies, such as cryo EM technology, in revealing the potential acid-resistant components have also been discussed.