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Journal of Bacteriology, August 1999, p. 5042-5050, Vol. 181, No. 16
Department of Plant and Microbial
Biology1 and Department of Molecular and
Cell Biology,2 University of California,
Berkeley, California 94720
Received 4 February 1999/Accepted 11 June 1999
Previous studies showed that Salmonella typhimurium
apparently senses external nitrogen limitation as a decrease in the
concentration of the internal glutamine pool. To determine whether the
inverse relationship observed between doubling time and the glutamine pool size in enteric bacteria was also seen in phylogenetically distant
organisms, we studied this correlation in Bacillus
subtilis, a gram-positive, sporulating bacterium. We measured the
sizes of the glutamine and glutamate pools for cells grown in batch culture on different nitrogen sources that yielded a range of doubling
times, for cells grown in ammonia-limited continuous culture, and for
mutant strains (glnA) in which the catalytic activity of
glutamine synthetase was lowered. Although the glutamine pool size of
B. subtilis clearly decreased under certain conditions of
nitrogen limitation, particularly in continuous culture, the inverse
relationship seen between glutamine pool size and doubling time in
enteric bacteria was far less obvious in B. subtilis. To
rule out the possibility that differences were due to the fact that
B. subtilis has only a single pathway for ammonia
assimilation, we disrupted the gene (gdh) that encodes the
biosynthetic glutamate dehydrogenase in Salmonella. Studies
of the S. typhimurium gdh strain in ammonia-limited
continuous culture and of gdh glnA double-mutant strains
indicated that decreases in the glutamine pool remained profound in
strains with a single pathway for ammonia assimilation. Simple working
hypotheses to account for the results with B. subtilis are
that this organism refills an initially low glutamine pool by
diminishing the utilization of glutamine for biosynthetic reactions and/or replenishes the pool by means of macromolecular degradation.
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Sensing of Nitrogen Limitation by Bacillus
subtilis: Comparison to Enteric Bacteria

*
Corresponding author. Mailing address: 111 Koshland
Hall, UC Berkeley, Berkeley, CA 94720-3102. Phone: (510) 643-9308. Fax: (510) 642-4995. E-mail: kustu{at}nature.berkeley.edu.
Present address: diaDexus, LLC, Santa Clara, CA 95054.
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