Lactobacillus casei 64H contains a phosphoenolpyruvate-dependent phosphotransferase system for uptake of galactose, as confirmed by analysis of ptsH and different gal mutants

• Published in: Journal of bacteriology Vol. 181; no. 1; pp. 225 - 230
• Main Authors: Bettenbrock, K, Siebers, U, Ehrenreich, P, Alpert, C A
• Format: Journal Article
• Language: English
• Published: United States American Society for Microbiology 01.01.1999; American Society for Microbiology (ASM)
• Subjects: Bacteria; Bacterial Proteins; Bacteriology; Biochemistry; Biological Transport, Active; Galactose - metabolism; Genes, Bacterial; Genetics; Kinetics; Lacticaseibacillus casei - genetics; Lacticaseibacillus casei - growth & development; Lacticaseibacillus casei - metabolism; Lactobacillus casei; Lactose - metabolism; Metabolism; Mutation; Phenotype; Phosphoenolpyruvate Sugar Phosphotransferase System - genetics; Phosphoenolpyruvate Sugar Phosphotransferase System - metabolism; Physiology and Metabolism
• ISSN: 0021-9193; 1098-5530
• DOI: 10.1128/JB.181.1.225-230.1999

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.