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Journal of Bacteriology, May 2001, p. 2957-2962, Vol. 183, No. 9
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.9.2957-2962.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Competence Regulation by Oxygen Availability and by Nox Is Not Related to Specific Adjustment of Central Metabolism in Streptococcus pneumoniae

Sabine Chapuy-Regaud,1 Frédérique Duthoit,1 Laurence Malfroy-Mastrorillo,1 Pierre Gourdon,2 Nic D. Lindley,2 and Marie-Claude Trombe1,*

Laboratoire de Génétique et Physiologie Bactérienne EA 3036, Centre Hospitalo-Universitaire de Rangueil, Université Paul Sabatier, 31403 Toulouse Cedex,1 and Centre de Bioingénierie Gilbert Durand, UMR INSA/CNRS and INSA/INRA, Institut National des Sciences Appliquées, 31077 Toulouse Cedex 4,2 France

Received 17 November 2000/Accepted 6 February 2001

In Streptococcus pneumoniae oxygen availability is a major determinant for competence development in exponentially growing cultures. NADH oxidase activity is required for optimal competence in cultures grown aerobically. The implication of oxidative metabolism and more specifically of Nox on central metabolism has been examined. Glycolytic flux throughout exponential growth revealed homolactic fermentation with a lactate production/glucose utilization ratio close to 2, whatever the aerobiosis level of the culture. Loss-of-function mutations in nox, which encodes NADH oxidase, did not change this trait. Consistently, mRNA levels of glyceraldehyde-3-phosphate dehydrogenase, L-lactate dehydrogenase, pyruvate oxidase, and NADH oxidase remained comparable to wild-type levels, as did the specific activities of key enzymes which control central metabolism. Competence regulation by oxygen involving the NADH oxidase activity is not due to significant modification of carbon flux through glycolysis. Failure to obtain loss-of-function mutation in L-ldh, which encodes the L-lactate dehydrogenase, indicates its essential role in pneumococci whatever their growth status.

* Corresponding author. Mailing address: Laboratoire de Génétique et Physiologie Bactérienne EA 3036, Centre Hospitalo-Universitaire de Rangueil, Université Paul Sabatier, 31403 Toulouse Cedex, France. Phone: 61 32 29 74. Fax: 61 32 26 20. E-mail: Trombe{at}CICT.FR.

Journal of Bacteriology, May 2001, p. 2957-2962, Vol. 183, No. 9
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.9.2957-2962.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


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