Identification of reference genes for quantitative Real-Time PCR in Bifidobacterium bifidum PRL2010 based on transcriptome analysis

In this study, we investigated the transcriptome of Bifidobacterium bifidum PRL2010 during in vitro growth by micro array technology. When B. bifidum PRL2010 was grown in liquid broth, 425 of the 1644 PRL2010 genes represented on the array were expressed in at least one of the three investigated growth phases, i.e., lag-, exponential and stationary phase. These transcriptional analyses identified a core in vitro transcriptome encompassing 150 genes, which resulted expressed in all phases. A proportion of the latter genes were further investigated as potential reference genes by Quantitative Real Time PCR (qRT-PCR) assays. Their expression stability was evaluated under different growth conditions, encompassing cultivation on different carbon sources, exposure to environmental stresses (thermal, acidic and osmotic) and growth phases. Our analyses validated six reference genes suitable for normalizing mRNA expression levels in qRT-PCR experiments applied to bifidobacteria. Transcriptional profiling of B.bifidum PRL2010 at different growth phases (lag phase, early exponential phase, late exponential phase, early stationary phase).