PMID:15466549

Citation	Abranches, J, Chen, YY and Burne, RA (2004) Galactose metabolism by Streptococcus mutans. Appl. Environ. Microbiol. 70:6047-52
Abstract	The galK gene, encoding galactokinase of the Leloir pathway, was insertionally inactivated in Streptococcus mutans UA159. The galK knockout strain displayed only marginal growth on galactose, but growth on glucose or lactose was not affected. In strain UA159, the sugar phosphotransferase system (PTS) for lactose and the PTS for galactose were induced by growth in lactose and galactose, although galactose PTS activity was very low, suggesting that S. mutans does not have a galactose-specific PTS and that the lactose PTS may transport galactose, albeit poorly. To determine if the galactose growth defect of the galK mutant could be overcome by enhancing lactose PTS activity, the gene encoding a putative repressor of the operon for lactose PTS and phospho-beta-galactosidase, lacR, was insertionally inactivated. A galK and lacR mutant still could not grow on galactose, although the strain had constitutively elevated lactose PTS activity. The glucose PTS activity of lacR mutants grown in glucose was lower than in the wild-type strain, revealing an influence of LacR or the lactose PTS on the regulation of the glucose PTS. Mutation of the lacA gene of the tagatose pathway caused impaired growth in lactose and galactose, suggesting that galactose can only be efficiently utilized when both the Leloir and tagatose pathways are functional. A mutation of the permease in the multiple sugar metabolism operon did not affect growth on galactose. Thus, the galactose permease of S. mutans is not present in the gal, lac, or msm operons.
Links	PubMed PMC522122 Online version:10.1128/AEM.70.10.6047-6052.2004
Keywords	Base Sequence; DNA, Bacterial/genetics; Galactokinase/genetics; Galactokinase/metabolism; Galactose/metabolism; Genes, Bacterial; Mutagenesis, Insertional; Operon; Phosphoenolpyruvate Sugar Phosphotransferase System/genetics; Phosphoenolpyruvate Sugar Phosphotransferase System/metabolism; Streptococcus mutans/genetics; Streptococcus mutans/growth & development; Streptococcus mutans/metabolism
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
STRMU:GAL1		GO:0006012: galactose metabolic process	ECO:0000315:		P		When compared to the doubling time of the wild type strain UA159 of Streptococcus mutans, the growth of JAM2, a galK deficient strain of Streptococcus mutans, had impaired growth equivalent to an organism grown in TV base medium with no added sugar. A measurement of the organism's optical density was used to measure growth. See table 2 for reference.	complete CACAO 3862
STRMU:GAL1	involved_in	GO:0006012: galactose metabolic process	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete

References

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