Ferroplasma acidiphilum is an acidophilic, autotrophic, ferrous iron-oxidizing, cell wall-lacking, mesophilic member of the Ferroplasmaceae. F. acidophilum is a mesophile with a temperature optimum of approximately 35 °C, growing optimally at a pH of 1.7. F. acidophilum is generally found in acidic mine tailings, primarily those containing pyrite (FeS2). It is especially abundant in cases of severe acid mine drainage, where other organisms such as Acidithiobacillus and Leptospirillum lower the pH of the environment to the extent that F. acidophilum is allowed to flourish.