title: A functional genomics approach to establish the complement of carbohydrate transporters in Streptococcus pneumoniae.
abstract: The aerotolerant anaerobe Streptococcus pneumoniae is part of the normal nasopharyngeal microbiota of humans and one of the most important invasive pathogens. A genomic survey allowed establishing the occurrence of twenty-one phosphotransferase systems, seven carbohydrate uptake ABC transporters, one sodium:solute symporter and a permease, underlining an exceptionally high capacity for uptake of carbohydrate substrates. Despite high genomic variability, combined phenotypic and genomic analysis of twenty sequenced strains did assign the substrate specificity only to two uptake systems. Systematic analysis of mutants for most carbohydrate transporters enabled us to assign a phenotype and substrate specificity to twenty-three transport systems. For five putative transporters for galactose, pentoses, ribonucleosides and sulphated glycans activity was inferred, but not experimentally confirmed and only one transport system remains with an unknown substrate and lack of any functional annotation. Using a metabolic approach, 80% of the thirty-two fermentable carbon substrates were assigned to the corresponding transporter. The complexity and robustness of sugar uptake is underlined by the finding that many transporters have multiple substrates, and many sugars are transported by more than one system. The present work permits to draw a functional map of the complete arsenal of carbohydrate utilisation proteins of pneumococci, allows re-annotation of genomic data and might serve as a reference for related species. These data provide tools for specific investigation of the roles of the different carbon substrates on pneumococcal physiology in the host during carriage and invasive infection.
authors.affiliation: Lab Microbiologia Molecolare e Biotecnologia, Dip Biologia Molecolare, Università di Siena, Siena, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Bidossi
authors.forename: Laura
authors.initials: L
authors.lastname: Mulas
authors.forename: Francesca
authors.initials: F
authors.lastname: Decorosi
authors.forename: Leonarda
authors.initials: L
authors.lastname: Colomba
authors.forename: Susanna
authors.initials: S
authors.lastname: Ricci
authors.forename: Gianni
authors.initials: G
authors.lastname: Pozzi
authors.forename: Josef
authors.initials: J
authors.lastname: Deutscher
authors.forename: Carlo
authors.initials: C
authors.lastname: Viti
authors.forename: Marco Rinaldo
authors.initials: MR
authors.lastname: Oggioni
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D050260:Carbohydrate Metabolism; D014644:Genetic Variation; D016680:Genome, Bacterial / Q000235:genetics*; D023281:Genomics / Q000379:methods; D046228:Microarray Analysis; D008969:Molecular Sequence Data; D010641:Phenotype; D010770:Phosphotransferases / Q000235:genetics / Q000378:metabolism*; D013296:Streptococcus pneumoniae / Q000235:genetics*; D013379:Substrate Specificity
chemical_list: D018528:ATP-Binding Cassette Transporters; D010770:Phosphotransferases