Bacterial

growth was assessed from culture turbidity at 600 nm (OD600). Cells were CP673451 concentration recovered during exponential phase (OD600 of 0.4) or early stationary phase (OD600 = 1.2), which was defined as the point where growth began to cease plus one period equivalent to the shortest generation time on that substrate. Bacteria were selleck chemicals llc also recovered 12, 24, 36, 48 or 72 h after the beginning of the stationary phase. For RNA isolation, 100 ml of culture was immediately harvested by centrifugation (at 15,000 × g for 1 min at 4°C) and the supernatant was decanted. Cell pellets were resuspended in 4 ml RNAprotect Bacteria Reagent (QIAGEN GmbH). After 5 min incubation, the suspensions were centrifuged again (at 5,000 × g for 5 min at room temperature); the supernatant was discarded and pellets were stored at -80°C. RNA isolation Prior to RNA extraction, pellets were slowly thawed, then resuspended in 0.5 ml TES buffer [10 mM Tris-HCl (pH 8.0), 1 mM EDTA, 100 mM NaCl], followed by addition of and mixing with 0.25 ml lysis solution [20 mM sodium acetate (pH 5.5), 1 mM EDTA, 0.5% SDS].

After that, see more the total RNA was further purified by the hot acid-phenol method as described previously [35]. RNA samples were purified from contaminating DNA by treatment with 50 U of DNase I (RNase free; Roche) during 1 h at 37°C. Finally, the RNA was dissolved in 50 μl diethylpyrocarbonate (DEPC)-treated water and quantified by absorbance at 260 and 280 nm on a NanoDrop spectrophotometer (Witec AG). The integrity of RNA was determined by agarose gel electrophoresis and the absence of DNA was verified by PCR. Reverse transcription PCR (RT-PCR) Reverse transcription was made on RNA isolated from cultures grown

with 3-chlorobenzoate, glucose or fructose, and harvested 24 h after the beginning of stationary phase. 0.5 μg of total RNA was denatured by heating at 65°C and reverse transcribed using the Omniscript RT kit (QIAGEN GmbH) following the instructions of the manufacturer, using primers listed in Additional file 1, Table S2. Primer designations refer to their exact position on ICEclc according to the numbering in AJ617740 (Genbank Accession number). 30 cycles of PCR amplification Tolmetin with the produced cDNA templates was performed with the HotStarTaq Master Mix kit (QIAGEN GmbH), using one tenth of volume from the reverse transcription reaction and 10 μM of a pair of specific primers (Additional file 1, Table S2). Amplification of regions between ORF94175 and inrR known to be co-transcribed served as positive control for the quality of the RT-PCR reaction. Finally, for each RNA sample, a PCR was performed without reverse transcriptase step, in order to control for the absence of DNA contamination. Mapping of transcriptional start sites The 5′ end of the transcript including inrR was mapped with the SMART RACE cDNA Amplification Kit (Clontech Laboratories, Inc.) according to the manufacturer’s protocol. cDNA was synthesized from 0.