The genes encoding Zymomonas mobilis pyruvate decarboxylase (pdc) and alcohol dehydrogenase II (adhB) were expressed in Bacillus subtilis YB886(pLOI500) under the control of a Bacillus SPO2 phage promoter and caused a 50% reduction of growth rate compared with the unmodified vector. Expression was further confirmed by Western blots, activity stains of native gels, and in vitro measurements of alcohol dehydrogenase activity. Additional strains of Bacillus were also transformed, and all produced similar but low levels of these enzymes. Although higher specific activities will be required for efficient ethanol production, no fundamental barriers exist to the expression of these Z. mobilis genes in Bacillus. Two abundant new proteins (ca. mass 33,000 daltons and 14,000 daltons) were observed in Coomassie Blue-stained gels; they are similar in size to the proteins induced by recombinant products in Escherichia coli.