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Journal of Bacteriology, January 1999, p. 225-230, Vol. 181, No. 1
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.

Lactobacillus casei 64H Contains a Phosphoenolpyruvate-Dependent Phosphotransferase System for Uptake of Galactose, as Confirmed by Analysis of ptsH and Different gal Mutants

Katja Bettenbrock,dagger Ulrike Siebers,Dagger Petra Ehrenreich, and Carl-Alfred Alpert*

Universität Osnabrück, Fachbereich Biologie/Chemie, AG Genetik, 49076 Osnabrück, Germany

Received 31 July 1998/Accepted 26 October 1998

Galactose metabolism in Lactobacillus casei 64H was analyzed by genetic and biochemical methods. Mutants with defects in ptsH, galK, or the tagatose 6-phosphate pathway were isolated either by positive selection using 2-deoxyglucose or 2-deoxygalactose or by an enrichment procedure with streptozotocin. ptsH mutations abolish growth on lactose, cellobiose, N-acetylglucosamine, mannose, fructose, mannitol, glucitol, and ribitol, while growth on galactose continues at a reduced rate. Growth on galactose is also reduced, but not abolished, in galK mutants. A mutation in galK in combination with a mutation in the tagatose 6-phosphate pathway results in sensitivity to galactose and lactose, while a galK mutation in combination with a mutation in ptsH completely abolishes galactose metabolism. Transport assays, in vitro phosphorylation assays, and thin-layer chromatography of intermediates of galactose metabolism also indicate the functioning of a permease/Leloir pathway and a phosphoenolpyruvate-dependent phosphotransferase system (PTS)/tagatose 6-phosphate pathway. The galactose-PTS is induced by growth on either galactose or lactose, but the induction kinetics for the two substrates are different.

* Corresponding author. Present address: Institut National de la Recherche Agronomique, Unité de Recherches sur la Viande, Domaine de Vilvert, 78352 Jouy-en-Josas, Cedex, France. Phone: 33 01 34 65 21 06. Fax: 33 01 34 65 21 05. E-mail: Alpert{at}biotec.jouy.inra.fr.

dagger Present address: Max-Planck-Intitut für Dynamik komplexer technischer Systeme, Zenit-Gebäude, 39120 Magdeburg, Germany.

Dagger Present address: Max-Planck-Institut für Neurobiologie, Abteilung Neurobiochemie, 82152 Martinsried, Germany.

Journal of Bacteriology, January 1999, p. 225-230, Vol. 181, No. 1
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.


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