The Role of Bacteria in the Formation of Acid from Certain Sul-

I This contribution is one of a series of papers by the Multiple Fellowship on Mine Acid Control sustained at Mellon Institute by the Sanitary Water Board, Department of Health, Commonwealth of Pennsylvania. catalyst. Indeed, Carpeniter and Heirndon (1933) suggested that bacterial activity by some sulfur oxidizing organism might explain, in part, the high acidities usually encountered in bituminous coal mine drainage. By chemical theory alone, they maintained, it was difficult to explain the rapid formation of acid in mines. Colmer and Hinkle (1947) postulated that Thiobacillus thiooxidans, or an unknown similar organism, was involved in the oxidation of sulfur and sulfur compounds in coal to form sulfuric acid. The same authors observed an unidentified bacterium to oxidize ferrous iron rapidly to the ferric state in acid mine waters. Leathen and Madison (1949) obtained T. thiooxidans in pure culture in elemental sulfur medium from all of the acid mine effluents examined. Iron oxidizing bacteria were isolated, also in pure culture, by the use of a new inorganic medium containing ferrous iron. This medium failed to support the growth of T. thiooxidans and was better suited for study of oxidation of ferrous iron than media containing "natural" mine water. The present study was designed to determine the role of both sulfur and iron oxidizing bacteria in acid formation from museum grade pyrite and marcasite, and from "sulfur balls", the most common sulfuritic constituent of bituminous coal. The role of T. thiooxidans in acid formation is reported herein, while the role of iron oxidizing bacteria isolated by us is the subject of Section II of this report.