AN IRON-OXIDIZING BACTERIUM FROM THE ACID DRAINAGE OF SOME BITUMINOUS COAL MINES

Abstract

A bacterium has been repeatedly isolated from acid mine drainage of some mines on Pittsburgh, Sewickley, and Upper Freeport bituminous coal seams which can bring about rapid oxidation of the drainage''s ferrous iron to ferric iron. In the drainage, sterilized by Seitz filtration, the iron remains in the ferrous state for long periods of time. The bacterium can bring about comparable changes in ferrous iron content of Seitz-filtered artificial acid mine drainage of pH 2.3 composed of distilled water, H2SO4, FeSO4 (2000 ppm.), and (NH4)2SO4 (100 ppm.). The bacterium is a small, Gram-negative, non-sporeforming rod. Growth in Waksman''s Na2S2O3 broth produces acid comparable to Thiobacillus thiooxidans. Growth on Na2So03 agar produces frosty-appearing colonies unlike those of T. thioparus or T. thiooxidans. Growth in acid mine water produces a rusty precipitate of an iron compound. Growth on acid mine water agar gives colonies with iron precipitation. The morph. characters of bacterium, and its auto trophic nature on thiosulfate medium with production of sulfuric acid to give low pH, indicate properties closely resembling those of the genus Thiobacillus. The mecha-nism responsible for oxidation of ferrous iron in natural and artificial acid mine waters has not yet been detd.