Nitrosomonas europaea cells treated with chloroform for one hour and compared to untreated cells

We analyzed the global transcriptional response of N. europaea when exposed to chloroform (7 µM for 1 h). Chloroform led to down regulation of 501 genes and up regulation of 251 genes. These up regulated genes included genes for heat shock proteins, sigmafactors of extracytoplasmic function subfamily and newly identified genes of toxin-antitoxin loci in N. europaea. Our study showed that despite a significant decrease of transcription in response to the stress, N. europaea expresses a plethora of defense genes when exposed to chloroform. Keywords: stress response, global transcription, toxin-antitoxin genes We selected chloroform concentrations and exposure times that caused significant changes in cell physiology but without them being too severe. Our experiments demonstrated that 7 uM chloroform caused the desired effect. Based on the physiological, proteomic and transcriptional observations, we analyzed the whole-genome transcriptional responses of N. europaea at 1 h after the chloroform treatment. Cells from treated samples and untreated control samples were collected for RNA extraction and hybridization with Affymetrix microarray GeneChip.