Production of Adenosine Triphosphate in Normal Cells and Sporulation Mutants of Bacillus subtilis

In sporulating Bacillus subtilis, the cellular concentration of ATP increases very little during vegetative growth in nutrient sporulation medium, shows a small peak at the end of growth, and then remains approximately constant during the developmental period. Therefore, ATP itself does not seem to control the onset of massive sporulation. ATP turns over rapidly because its concentration decreases to one-twentieth of the original value in less than 1 min after replacement of air by nitrogen. Sporulation mutants blocked in the citric acid cycle are unable to maintain the normal ATP concentration after growth has stopped. ATP synthesis is not restored by the addition of acetate or citric acid cycle compounds preceding the block, but it is restored by cycle compounds following the block or by other carbon sources. Other sporulation mutants blocked in some reaction necessary to provide acetyl coenzyme A during the developmental period are also unable to maintain ATP after cessation of growth, but their ATP synthesis is restored by any metabolizable carbon source, including acetate or citric acid cycle compounds. Finally, mutants blocked in the Embden-Meyerhof path or in the pyruvate dehydrogenase complex continue to maintain ATP after growth in nutrient sporulation medium has stopped. The measurement of ATP and its response to different compounds can therefore be used to classify sporulation mutants and to localize on the biochemical chart the pathways that may be affected by the mutation.