acidtolerant

Acidtolerant is an adjective used in biology to describe organisms, enzymes, or biological systems that can survive, function, or grow in environments with low pH. It is commonly applied to microorganisms and to plants or soils affected by acidity. The term is distinct from acidophilic, which denotes a preference for acidic conditions, and from aciduric, which denotes tolerance to acidity without necessarily thriving.

In microbiology, acid tolerance refers to the ability of organisms to endure low pH environments. Many bacteria employ multiple strategies, including actively pumping protons out of the cytoplasm, regulating membrane permeability, and producing acid shock proteins. The glutamate decarboxylase Gad system is a well-studied example that consumes intracellular protons to raise cytoplasmic pH. Other mechanisms include adjusting fatty acid composition of membranes and activating DNA repair pathways. Some acid tolerance responses are inducible, developing in reaction to acidic stress.

Examples include lactic acid bacteria such as Lactobacillus and certain yeasts that play roles in fermentation and biotechnology. Pathogens such as Helicobacter pylori also exhibit strong acid tolerance, enabling survival in the stomach. Environmental bacteria can tolerate acidic soils or waters, contributing to acid-stress ecology.

Ecological and practical relevance: acid tolerance shapes microbial communities, fermentation processes, and bioremediation efforts. Understanding acid tolerance informs the selection of probiotic strains, optimization of fermentation, and agricultural practices for managing acidic soils. Acidtolerant does not necessarily imply optimal growth at low pH unless the organism is described as acidophilic; it often denotes survival or growth within a range of acidic conditions.