Fig. 7

Adherent pneumococci gain access to host-derived carbohydrates and activate non-glucose sugar importers. a There were 295 genes differentially expressed between pneumococcal strains exposed to epithelial cells: 118 unique genes of the 295 genes were activated in ∆cps2E compared to wild type (wt) pneumococci while 185 unique genes were repressed. Note that eight genes showed activation and repression at different time points. b Most of the differentially expressed genes are of unknown function (83 genes, 28 % of 295), followed by cellular transport (41 genes, 14 %), amino acid metabolism (14 genes, 5 %), and DNA replication, repair, and recombination (14 genes, 5 %). Note that an individual gene can be part of multiple classes. c Of the 41 transporter genes, 16 are described to transport carbohydrates. The carbohydrate importers transport a wide range of carbohydrates, from simple monosaccharides to complex polysaccharides. d At 60 mpi, the expression of glucose transporters (manLM, blue boxes) was repressed (p < 0.05, FC = 1.5) in ∆cps2E compared to encapsulated S. pneumoniae. Eight non-glucose transporters were activated (p < 0.05, FC > 2) in the ∆cps2E strain: SPD_0089, celC, SPD_0295, SPD_0232/33/34, rafE, and malD. e We validated the data by qRT-PCR for three sugar importers: malD (polysaccharides), rafE (oligosaccharide), and SPD_0234 (non-glucose disaccharide). By removing epithelial mucus prior to infection, the importers were no longer activated in ∆cps2E compared to wild type (FC < 2, Washed). Incubation with type III porcine mucin (5 g/L) did not activate the genes in ∆cps2E compared to encapsulated pneumococci (FC < 2)