Effect of CORM-2 on E. coli transcriptome

We recently reported that carbon monoxide (CO) has bactericidal activity. To understand its mode of action we analysed the gene expression changes occurring when Escherichia coli, grown aerobically and anaerobically, is treated with the carbon monoxide releasing molecule, CORM-2. The E. coli microarray analysis shows that E. coli CORM-2 response is multifaceted with a high number of differentially regulated genes spread through several functional categories, namely genes involved in inorganic ion transport and metabolism, regulators, and genes implicated in posttranslational modification, such as chaperones. CORM-2 has higher impact in E. coli cells grown anaerobically, as judged by the existence of repressed genes belonging to eight functional classes which are absent in aerobically CORM-2 treated cells. In spite of the relatively stable nature of the CO molecule, our results show that CO is able to trigger a significant alteration in the transcriptome of E. coli which necessarily has effects in several key metabolic pathways. Total RNA from two independent cultures of cells grown either aerobically or anaerobically and treated with 250 μM CORM-2 during 15 min or left untreated were processed for use in the Affymetrix GeneChip E. coli Genome 2.0 Arrays, according to the manufacturer’s instructions. Arrays were scanned in an Affymetrix GeneChip scanner 2500 and analysed first with Affymetrix MAS 5.0 software to obtain Absent/Present calls and to assure that all quality parameters were within the recommended range. Hybridization, scanning and detection procedures were done at the Genomics Unit of Instituto Gulbenkian de Ciência (Portugal).