title: Lactose-over-glucose preference in Bifidobacterium longum NCC2705: glcP, encoding a glucose transporter, is subject to lactose repression.
abstract: Analysis of culture supernatants obtained from Bifidobacterium longum NCC2705 grown on glucose and lactose revealed that glucose utilization is impaired until depletion of lactose. Thus, unlike many other bacteria, B. longum preferentially uses lactose rather than glucose as the primary carbon source. Glucose uptake experiments with B. longum cells showed that glucose transport was repressed in the presence of lactose. A comparative analysis of global gene expression profiling using DNA arrays led to the identification of only one gene repressed by lactose, the putative glucose transporter gene glcP. The functionality of GlcP as glucose transporter was demonstrated by heterologous complementation of a glucose transport-deficient Escherichia coli strain. Additionally, GlcP exhibited the highest substrate specificity for glucose. Primer extension and real-time PCR analyses confirmed that expression of glcP was mediated by lactose. Hence, our data demonstrate that the presence of lactose in culture medium leads to the repression of glucose transport and transcriptional down-regulation of the glucose transporter gene glcP. This may reflect the highly adapted life-style of B. longum in the gastrointestinal tract of mammals.
authors.affiliation: Nestlé Research Center, Vers-chez-les-Blanc, 1000 Lausanne 26, Switzerland.
authors.forename: Stephan
authors.initials: S
authors.lastname: Parche
authors.forename: Manfred
authors.initials: M
authors.lastname: Beleut
authors.forename: Enea
authors.initials: E
authors.lastname: Rezzonico
authors.forename: Doris
authors.initials: D
authors.lastname: Jacobs
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Arigoni
authors.forename: Fritz
authors.initials: F
authors.lastname: Titgemeyer
authors.forename: Ivana
authors.initials: I
authors.lastname: Jankovic
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D001644:Bifidobacterium / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D001692:Biological Transport; D003470:Culture Media; D021901:DNA, Intergenic / Q000235:genetics; D015536:Down-Regulation / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005947:Glucose / Q000378:metabolism*; D051246:Glucose Transport Proteins, Facilitative / Q000235:genetics; D007785:Lactose / Q000502:physiology*; D008969:Molecular Sequence Data; D010733:Phosphoglucomutase / Q000235:genetics; D013379:Substrate Specificity; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D021901:DNA, Intergenic; D051246:Glucose Transport Proteins, Facilitative; D010733:Phosphoglucomutase; D005947:Glucose; D007785:Lactose