Appl Environ Microbiol, January 1998, p. 74-81, Vol. 64, No. 1
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Laboratoire de Synthèse,
Received 30 May 1997/Accepted 19 September 1997
We investigated the carbon metabolism of three strains of
Fibrobacter succinogenes and one strain of
Fibrobacter intestinalis. The four strains produced the
same amounts of the metabolites succinate, acetate, and formate in
approximately the same ratio (3.7/1/0.3). The four strains similarly
stored glycogen during all growth phases, and the glycogen-to-protein
ratio was close to 0.6 during the exponential growth phase.
13C nuclear magnetic resonance (NMR) analysis of
[1-13C]glucose utilization by resting cells of the four
strains revealed a reversal of glycolysis at the triose phosphate level
and the same metabolic pathways. Glycogen futile cycling was
demonstrated by 13C NMR by following the simultaneous
metabolism of labeled [13C]glycogen and exogenous
unlabeled glucose. The isotopic dilutions of the CH2 of
succinate and the CH3 of acetate when the resting cells
were metabolizing [1-13C]glucose and unlabeled glycogen
were precisely quantified by using 13C-filtered
spin-echo difference 1H NMR spectroscopy. The measured
isotopic dilutions were not the same for succinate and acetate; in the
case of succinate, the dilutions reflected only the contribution of
glycogen futile cycling, while in the case of acetate, another
mechanism was also involved. Results obtained in complementary
experiments are consistent with reversal of the succinate
synthesis pathway. Our results indicated that for all of the strains,
from 12 to 16% of the glucose entering the metabolic pathway
originated from prestored glycogen. Although genetically diverse, the
four Fibrobacter strains studied had very similar carbon
metabolism characteristics.
*
Corresponding author. Mailing address for Anne-Marie
Delort: Laboratoire de Synthèse, Electrosynthèse et Etude
de Systèmes à Intérêt Biologique, UMR
6504-CNRS, Université Blaise-Pascal, 63177, Aubière,
France. Phone: (33) 04 73 40 77 14. Fax: (33) 04 73 40 77 17. E-mail:
amdelort{at}chimtp.univ-bpclermont.fr. Mailing address for
Evelyne Forano: Laboratoire de Microbiologie, Institut National de la
Recherche Agronomique, Centre de Recherches de Clermont-Ferrand-Theix, 63122 Saint-Genès-Champanelle,
France. Phone: (33) 04 73 62 42 48. Fax: (33) 04 73 62 45 81. E-mail: forano{at}clermont.inra.fr.
Present address: Central Laboratories, Slovak Technical University,
81237 Bratislava, Slovakia.
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