Project description: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.
Project description: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. 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.)
Project description:BACKGROUND:Isobutanol is a promising next generation biofuel with demonstrated high yield microbial production, but the toxicity of this molecule reduces fermentation volumetric productivity and final titers. Organic solvent tolerance is a complex, multigenic phenotype that has been recalcitrant to rational engineering approaches. We apply experimental evolution followed by genome resequencing and a gene expression study to elucidate genetic bases on adaptation to exogenous isobutanol stress. RESULTS:The adaptations acquired in our evolved lineages exhibit antagonistic pleiotropy between minimal and rich medium, and appear to be specific to the effects of longer chain alcohols. By examining genotypic adaptation in multiple independent lineages, we find evidence of parallel evolution in hfq, mdh, acrAB, gatYZABCD, and rph genes. Many isobutanol tolerant lineages show reduced rpoS activity, perhaps related to mutations in hfq or acrAB. Consistent with the complex, multigenic nature of solvent tolerance, we observe adaptations in a diversity of cellular processes. Many adaptations appear to involve epistasis between different mutations, implying a rugged fitness landscape for isobutanol tolerance. We observe a trend of evolution targeting post-transcriptional regulation and high centrality nodes of biochemical networks. Collectively, the genotypic adaptations we observe suggest mechanisms of adaptation to isobutanol stress based on remodelling the cell envelope and surprisingly, stress response attenuation. CONCLUSIONS:We have discovered a set of genotypic adaptations that confer increased tolerance to exogenous isobutanol stress. Our results are immediately useful to efforts to engineer more isobutanol tolerant host strains of E. coli for isobutanol production. We suggest that rpoS and post-transcriptional regulators, such as hfq, RNA helicases, and sRNAs may be interesting mutagenesis targets for futurue global phenotype engineering.
Project description:BACKGROUND:Isobutanol is a promising next generation biofuel with demonstrated high yield microbial production, but the toxicity of this molecule reduces fermentation volumetric productivity and final titers. Organic solvent tolerance is a complex, multigenic phenotype that has been recalcitrant to rational engineering approaches. We apply experimental evolution followed by genome resequencing and a gene expression study to elucidate genetic bases on adaptation to exogenous isobutanol stress. RESULTS:The adaptations acquired in our evolved lineages exhibit antagonistic pleiotropy between minimal and rich medium, and appear to be specific to the effects of longer chain alcohols. By examining genotypic adaptation in multiple independent lineages, we find evidence of parallel evolution in hfq, mdh, acrAB, gatYZABCD, and rph genes. Many isobutanol tolerant lineages show reduced rpoS activity, perhaps related to mutations in hfq or acrAB. Consistent with the complex, multigenic nature of solvent tolerance, we observe adaptations in a diversity of cellular processes. Many adaptations appear to involve epistasis between different mutations, implying a rugged fitness landscape for isobutanol tolerance. We observe a trend of evolution targeting post-transcriptional regulation and high centrality nodes of biochemical networks. Collectively, the genotypic adaptations we observe suggest mechanisms of adaptation to isobutanol stress based on remodelling the cell envelope and surprisingly, stress response attenuation. CONCLUSIONS:We have discovered a set of genotypic adaptations that confer increased tolerance to exogenous isobutanol stress. Our results are immediately useful to efforts to engineer more isobutanol tolerant host strains of E. coli for isobutanol production. We suggest that rpoS and post-transcriptional regulators, such as hfq, RNA helicases, and sRNAs may be interesting mutagenesis targets for futurue global phenotype engineering. Two strains (WT strain and G3.2 mutant strain), each with two culture conditions (with and without isobutanol in medium). Three biological replicates for each strain/culture condition. Twelve samples in total.
Project description:The response to acidity is crucial for neutralophilic bacteria. Escherichia coli has a well characterized regulatory network to induce multiple defense mechanisms against excess of protons. Nevertheless, systemic studies of the transcriptional and translational reprogramming of E. coli to different acidic strengths have not yet been performed. Here, we used ribosome profiling and mRNA sequencing to determine the response of E. coli to pH 7.6, 5.8 and 4.4. Data were analyzed using the high-throughput HRIBO pipeline and previously undetected adaptations of E. coli to acid stress were found including up-regulation of glycerol catabolism and siderophore production, down-regulation of many membrane proteins and regulation by the transcriptional regulators YdeO, MhpR, IscR, and YdcI. Several examples of differential transcriptional and translational regulation of genes were identified as well as potential novel small open reading frames. These results expand the acid resistance network and provide new insights into the fine-tuned response of E. coli.
Project description:The purpose of this study is to determine whether the presence of pathogenic Escherichia coli in colon is associated with psychiatric disorders.
Project description:Transcriptional profiling of E. coli cells comparing control harboring the empty vector pRadGro (Ec-pR) with E. coli expressing the Deinococcus radiodurans response regulator DR1558 (Ec-1558) Expression of DR1558 conferred to multi-stress tolerance to E. coli.
Project description:Despite the characterization of many aetiologic genetic changes. The specific causative factors in the development of sporadic colorectal cancer remain unclear. This study was performed to detect the possible role of Enteropathogenic Escherichia coli (EPEC) in developing colorectal carcinoma.