Identification of isobutanol response network of E. coli. Escherichia coli

Isobutanol has emerged as a potential biofuel due to recent metabolic engineering efforts. Here we used gene expression and transcription factor(TF)-gene interaction data, genetic knockouts, and Network Component Analysis (NCA) to map the isobutanol response network of Escherichia coli under aerobic conditions. A transcriptional response network consisting of 2004 genes/TFs and 2600 interactions was identified. Through further investigation ArcA, Fur, and PhoB were demonstrated to be important mediators of this response. In addition, the ethanol, n-butanol, and isobutanol response networks were compared in order to identify common and distinct toxicity features associated with these three alcohol based biofuels. Overall design: E. coli was grown aerobically at 37C in minimal MOPS media with 0.2% glucose as the sole carbon source. At mid-log, the cultures were split in half with one half receiving a 1% isobutanol, 1% n-butanol, or 3% ethanol (vol/vol) treatment, while the other half remained unperturbed. After 10 minutes of continued growth cultures were harvested. Total RNA was purified using a Qiagen RNeasy midikit, and labeled indirectly with amino-allyl dUTP. Every experiment had a minimum of 4 biological replicates, each with 2 technical replicates (8 arrays/experiment). Normalized log10 expression ratios were obtained from lcDNA implemented with quality filtering (receptor.seas.ucla.edu/lcDNA; Hyduke DR, Rohlin L, Kao KC, Liao JC. 2003 A software package for cDNA microarray data normalization and assessing confidence intervals. OMICS 7(3):227-234.)