Acidophile definition

A microorganism that grows at acidic pHs below 4. (Alcamo’s Fundamentals of Microbiology)

An organism that grows best at acidic pH values. (Brock Biology of Microorganisms)

A bacterium that grows below pH 4. (Microbiology: An Introduction by Tortora, Funke, and Case)

A microorganism that has its growth optimum between about pH 0 and 5.5. (Prescott’s Microbiology)