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Journal of Bacteriology, June 2000, p. 3088-3096, Vol. 182, No. 11
Institute of Biotechnology 1, Research Center
Jülich, D-52425 Jülich, Germany
Received 18 October 1999/Accepted 6 March 2000
Growth of Corynebacterium glutamicum on mixtures of the
carbon sources glucose and acetate is shown to be distinct from growth on either substrate alone. The organism showed nondiauxic growth on
media containing acetate-glucose mixtures and simultaneously metabolized these substrates. Compared to those for growth on acetate
or glucose alone, the consumption rates of the individual substrates
were reduced during acetate-glucose cometabolism, resulting in similar
total carbon consumption rates for the three conditions. By
13C-labeling experiments with subsequent nuclear
magnetic resonance analyses in combination with metabolite balancing,
the in vivo activities for pathways or single enzymes in the central
metabolism of C. glutamicum were quantified for growth on
acetate, on glucose, and on both carbon sources. The activity of the
citric acid cycle was high on acetate, intermediate on acetate plus
glucose, and low on glucose, corresponding to in vivo activities
of citrate synthase of 413, 219, and 111 nmol · (mg of
protein)
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Quantitative Determination of Metabolic Fluxes during
Coutilization of Two Carbon Sources: Comparative Analyses with
Corynebacterium glutamicum during Growth on Acetate
and/or Glucose
1 · min
1, respectively. The
citric acid cycle was replenished by carboxylation of
phosphoenolpyruvate (PEP) and/or pyruvate (30 nmol · [mg of protein]
1 · min
1) during growth on
glucose. Although levels of PEP carboxylase and pyruvate carboxylase
during growth on acetate were similar to those for growth on glucose,
anaplerosis occurred solely by the glyoxylate cycle (99 nmol · [mg of protein]
1 · min
1).
Surprisingly, the anaplerotic function was fulfilled completely by the
glyoxylate cycle (50 nmol · [mg of
protein]
1 · min
1) on glucose plus
acetate also. Consistent with the predictions deduced from the
metabolic flux analyses, a glyoxylate cycle-deficient mutant of
C. glutamicum, constructed by targeted deletion of the isocitrate lyase and malate synthase genes, exhibited impaired growth
on acetate-glucose mixtures.
*
Corresponding author. Mailing address: Institute of
Biotechnology 1, Research Center Jülich, D-52428 Jülich,
Germany, Phone: 49-2461-615169. Fax: 49-2461-612710. E-mail:
v.wendisch{at}fz-juelich.de.
Dedicated to Rudolf K. Thauer on the occasion of his 60th birthday.
Present address: Abt. Mikrobiologie und Biotechnologie, University
of Ulm, D-89061 Ulm, Germany.
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