Requirement for Acetate and Glycine (or Serine) for Sporulation Without Growth of Bacillus subtilis.
Cells of Bacillus subtilis sporulate when they are transferred, at any time of growth in nutrient sporulation medium, to a potassium-phosphate buffer containing slowly utilizable carbon sources such as l-aspartate, citrate, l-glutamate, or lactate. Transfer to buffer containing more rapidly utilizable carbon sources such as malate or glucose leads to sporulation only when the cells either had reached the end of growth or when the transfer medium also contains glycine. Acetate, which as a sole carbon source does not allow growth, also does not alone permit sporulation; however, the presence of both acetate (0.05 m) and glycine or l-serine (0.01 m) in the buffer medium allows sporulation if the cells are transferred to this medium after they have grown in the nutrient sporulation medium beyond the end of the exponential growth phase (T(0)). The development, required before transfer, does not seem to involve the end of a round of deoxyribonucleic acid duplication, as experiments with tryptophan-starved cells have indicated. Glycine or serine cannot be replaced by any of the known metabolites, which are partially derived from them. Amino acid analysis of nutrient sporulation medium showed that glycine (but not serine) is present at a concentration of 0.3 mm at the beginning of the developmental period, thus allowing, in combination with an acetyl-coenzyme A (CoA) precursor, sporulation but not growth. Acetyl-CoA is required not only for adenosine-triphosphate synthesis but also for some other reactions.
Laboratory of Molecular Biology, National Institute of Neurological Diseases and Stroke, Bethesda, Maryland 20014.
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Freese