Relative transcription levels of pilus-encoding genes from B. bifidum PRL2010, B. adolescentis ATCC15703, B. dentium Bd1 and B. animalis subsp. lactis DSM10140 upon cultivation in MRS supplemented with various carbon sources (lactose, FOS, N-acetylglucosamine, mucin), or bovine milk, versus growth in MRS supplemented with glucose as unique carbon source as analysed by quantitative real-time PCR assays. The histograms indicate the relative amounts of the pilin/sortase mRNAs for the specific samples. In each panel, the ORF numbering indicates the gene code according to Figure 1. The values on the y-axes as well as the value (between brackets) represent the fold fold change relative to reference genes as indicated in the materials and method section. For B. dentium Bd1 qRT-PCR experiments were performed only on those pili-encoding loci, i.e., pil2, pil5 and pil6, which display a typical gene constellation of the pilus locus (see Figure 2).