production of Thiobacillus denitrificans for the enzyme rhodanese. Appl. Microbiol. 14:998-1003. 1966.-A method for the anaerobic growth of 7hiobacillus denitrificans in a 140-liter (total capacity) stainless-steel culture vessel is described. As a result of controlling the pH value of cultures, and of ensuring that certain essential nutrients were in excess, cell yields approaching 700 mg (dry weight) per liter were obtained. These were over threefold higher than the best yields hitherto reported. The average rhodanese content of the cells from four cultures was 176,000 units per gram (dry weight). Adenosine-5'-phosphosulfate reductase (average content, 238 units per gram dry weight) and adenylate kinase (average content, 15,300 units per gram, dry weight) were also present. Earlier methods of cultivating Thiobacillus denitrificans under anaerobic conditions were based on use of the medium of Baalsrud and Baalsrud (2), which contains: NH4Cl, 0.05%; 998 Vol. 14, No. 6