, 2008). An untreated control was included. Bacteria were collected after 20 min of treatment before significant growth differences were observed due to the antimicrobial effect of the drugs. It is noted that we observed a weak growth inhibition at the two highest concentrations of thioridazine. Total RNA was prepared by a hot acid–phenol procedure (Moazed et GSK-3 inhibitor review al., 1986). Total nucleic acid concentrations and purity were estimated using absorbance readings (260 nm/280 nm) on a NanoDrop (Saveen Werner). The genes were analyzed by either Northern blotting or primer extension. For genes larger than 1000 bp we performed primer extensions to obtain

a clear result. Primer extension analyses Metformin chemical structure were performed as described previously (Klitgaard et al., 2008) and Northern blot analyses were carried out as described elsewhere (Nielsen et al., 2010). All primers and DNA probes used for primer extension and Northern

blot analyses, respectively (Table 1), were labelled at the 5′ end with 32P γATP. The primer extension and Northern blot products were visualized by autoradiography and/or phosphor imaging using a Typhoon scanner (GE Healthcare). Spot intensities were quantified using imagequant 5.0 software (Molecular Dynamics) and gene expression ratios were calculated relative to the untreated control. Expression levels on Northern blots were normalized to the 16S rRNA gene levels on the reprobed membrane preliminary to the calculation of expression ratios. Treatments were compared with the untreated control and only changes of at least twofold up- or downregulation were considered. Expression of the mecA gene has previously been shown to be induced by oxacillin and to be reduced yet again when oxacillin was

combined with thioridazine (Klitgaard et al., 2008). Related to this, it was interesting to comprehend whether other PBPs and genes involved in β-lactam resistance were affected by the combinatorial treatment or if the effect was specific to the non-native PBP2a. pbpB is transcribed from three different promoters: P1 and P1′ are located upstream of the first gene in the operon (recU) and the VraSR-regulated P2 is located immediately upstream of pbpB; the latter will be described in coherence Amylase with the VraSR regulon below. The distal P1 and P1′ promoters of pbpB were unaffected by the drug addition (Fig. 2a and b) besides a slight induction of pbpB P1′ by oxacillin as observed previously (Utaida et al., 2003). In contrast, the level of pbpD transcript was reduced at the highest concentrations of thioridazine (Fig. 2c). The femAB gene products were induced by oxacillin. This induction was further increased by addition of low concentrations of thioridazine; however, at higher thioridazine concentrations the induction is diminished (Fig. 2d).