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Applied and Environmental Microbiology, January 2001, p. 33-41, Vol. 67, No. 1
0099-2240/01/$04.00+0   DOI: 10.1128/AEM.67.1.33-41.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Relationship between Glycolysis and Exopolysaccharide Biosynthesis in Lactococcus lactis

Ana Ramos,1 Ingeborg C. Boels,2 Willem M. de Vos,2 and Helena Santos1,*

Instituto de Tecnologia Química e Biológica/Universidade Nova de Lisboa and Instituto de Biologia Experimental e Tecnológica, 2780-156 Oeiras, Portugal,1 and NIZO Food Research and Wageningen Centre for Food Sciences, 6710 BA Ede, The Netherlands2

Received 15 May 2000/Accepted 10 October 2000

The relationships between glucose metabolism and exopolysaccharide (EPS) production in a Lactococcus lactis strain containing the EPS gene cluster (Eps+) and in nonproducer strain MG5267 (Eps-) were characterized. The concentrations of relevant phosphorylated intermediates in EPS and cell wall biosynthetic pathways or glycolysis were determined by 31P nuclear magnetic resonance. The concentrations of two EPS precursors, UDP-glucose and UDP-galactose, were significantly lower in the Eps+ strain than in the Eps- strain. The precursors of the peptidoglycan pathway, UDP-N-acetylglucosamine and UDP-N-acetylmuramoyl-pentapeptide, were the major UDP-sugar derivatives detected in the two strains examined, but the concentration of the latter was greater in the Eps+ strain, indicating that there is competition between EPS synthesis and cell growth. An intermediate in biosynthesis of histidine and nucleotides, 5-phosphorylribose 1-pyrophosphate, accumulated at concentrations in the millimolar range, showing that the pentose phosphate pathway was operating. Fructose 1,6-bisphosphate and glucose 6-phosphate were the prominent glycolytic intermediates during exponential growth of both strains, whereas in the stationary phase the main metabolites were 3-phosphoglyceric acid, 2-phosphoglyceric acid, and phosphoenolpyruvate. The activities of relevant enzymes, such as phosphoglucose isomerase, alpha -phosphoglucomutase, and UDP-glucose pyrophosphorylase, were identical in the two strains. 13C enrichment on the sugar moieties of pure EPS showed that glucose 6-phosphate is the key metabolite at the branch point between glycolysis and EPS biosynthesis and ruled out involvement of the triose phosphate pool. This study provided clues for ways to enhance EPS production by genetic manipulation.

* Corresponding author. Mailing address: Instituto de Tecnologia Química e Biológica/Universidade Nova de Lisboa, Rua da Quinta Grande, 6, Apt. 127, 2780-156 Oeiras, Portugal. Phone: 351-21-4469828. Fax: 351-21-4428766. E-mail: santos{at}itqb.unl.pt.

Applied and Environmental Microbiology, January 2001, p. 33-41, Vol. 67, No. 1
0099-2240/01/$04.00+0   DOI: 10.1128/AEM.67.1.33-41.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


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