The Bacillus subtilis men genes encode biosynthetic enzymes for formation of the respiratory chain component menaquinone. The menp1 promoter previously was shown to be the primary cis element for menFD gene expression. In the present work, it was found that either supplementation with nonfermentable carbon sources or reutilization of glycolytic end products increased menp1 activity in the late postexponential phase. The effect on menp1 activity by a particular end product (such as acetoin or acetate) was prevented by blocking the corresponding pathway for end product utilization. Alteration of a TGAAA motif within the promoter region resulted in unregulated menp1 activity throughout the culture cycle, irrespective of the carbon source added.