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J. Bacteriol., Dec 1997, 7351-7359, Vol 179, No. 23
JE Craig, MJ Ford, DC Blaydon and AL Sonenshein
The citB gene of Bacillus subtilis encodes aconitase, the enzyme of the
Krebs citric acid cycle, which is responsible for the interconversion of
citrate and isocitrate. A B. subtilis strain with an insertion mutation in
the citB gene was devoid of aconitase activity and aconitase protein,
required glutamate for growth in minimal medium, and was unable to
sporulate efficiently in nutrient broth sporulation medium. Mutant cells
failed to form the asymmetric septum characteristic of sporulating cells
and were defective in transcription of the earliest-expressed spo genes,
that is, the genes dependent on the Spo0A phosphorelay. However, this early
block in sporulation was partially overcome when cells of the citB mutant
were induced to sporulate by resuspension in a poor medium. Accumulation of
citrate in the mutant cells or in their culture fluid may be responsible
for the early block, possibly because citrate can chelate divalent cations
needed for the activity of the phosphorelay.
Copyright © 1997, American Society for Microbiology
A null mutation in the Bacillus subtilis aconitase gene causes a block in Spo0A-phosphate-dependent gene expression
Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
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