Our research primarily involves Clostridium which is a species containing strains with the rare ability To produce the useful chemical isopropanol, in addition to acetone, butanol and ethanol. In related studies, we also included another solvent-producing organism, and Bacillus macerans, which is a facultative anaerobe and produces a high level of acetone and ethanol under anaerobic conditions. Because B. macerans does not produce butyric ac id or butanol, it provides a simpler system for the study of the acetoacetyl-CoA-reacting enzymes and also an organism outside the clostridial group for a mechanistic study of the solventogenic switch. The objectives for this report period were to purify and characterize distinct forms of alcohol dehydrogenases; to purify and characterize acetoacetyl-CoA-reacting enzymes; and to study the organization of solvent-production genes.