Metabolic diversity and adaptive mechanisms of iron- and/or sulfur-oxidizing autotrophic acidophiles in extremely acidic environments.

Many studies have investigated the mechanisms underlying the survival and growth of certain organisms in extremely acidic environments known to be harmful to most prokaryotes and eukaryotes. Acidithiobacillus and Leptospirillum spp. are dominant bioleaching bacteria widely used in bioleaching systems, which are characterized by extremely acidic environments. To survive and grow in such settings, these acidophiles utilize shared molecular mechanisms that allow life in extreme conditions. In this review, we have summarized the results of published genomic analyses, which underscore the ability of iron- and/or sulfur-oxidizing autotrophic acidophiles belonging to the genera Acidithiobacillus and Leptospirillum to adapt to acidic environmental conditions. Several lines of evidence point at the metabolic diversity and multiplicity of pathways involved in the survival of these organisms. The ability to thrive in adverse environments requires versatile activation of structural and functional adaptive responses, including bacterial adhesion, motility, and resistance to heavy metals. We have highlighted recent developments centered on the key survival mechanisms employed by dominant extremophiles, and have laid the foundation for future studies focused on the ability of acidophiles to thrive in extremely acidic environments.