Project description:One longstanding question in microbiology is how microbes buffer perturbations in energy metabolism. In this study, we systematically analyzed the impact of different levels of ATP demand in Escherichia coli under various conditions (aerobic and anaerobic, with and without cell growth). One key finding is that, under all conditions tested, the glucose uptake increases with rising ATP demand, but only to a critical level beyond which it drops markedly, even below wild-type levels. Focusing on anaerobic growth and using metabolomics and proteomics data in combination with a kinetic model, we show that this biphasic behavior is induced by the dual dependency of the phosphofructokinase on ATP (substrate) and ADP (allosteric activator). This mechanism buffers increased ATP demands by a higher glycolytic flux but, as shown herein, it collapses under very low ATP concentrations. Model analysis also revealed two major rate-controlling steps in the glycolysis under high ATP demand, which could be confirmed experimentally. Our results provide new insights on fundamental mechanisms of bacterial energy metabolism and guide the rational engineering of highly productive cell factories.
Project description:Comparative analysis of changes in gene and protein expression and fatty acid profiles between Escherichia coli K-12 MG1655 ΔfadD ΔaraBAD expressing an acyl-acyl carrier protein thioesterase from Umbellularia californica (BTE) or a non-functional mutant thioesterase (BTE-H204A) to determine the functional basis for losses in cell viability, membrane integrity, or other stresses and metabolic perturbations that may be present. New hypotheses obtained from the study will assist in metabolic engineering efforts of improved strains exhibiting higher fatty acid yields and productivities.
Project description:Escherichia coli DH1 cultures with treated with 6% 1,4 Butanediol for 1 hour and compared with untreated cultures The data from this experiment was used to identify a candidate for further study as described in Szmidt et al 2013 Utilizing a highly responsive gene, yhjX, in E. coli based production of 1,4-Butanediol submitted to Chemical Engineering Science
Project description:Cellular metabolism controls gene expression through allosteric interactions between metabolites and transcription factors. Methods to detect these regulatory interactions are mostly based on in vitro binding assays, but there are no methods to identify them at a genome-scale in vivo. Here we show that dynamic transcriptome and metabolome data identify metabolites that are potential effectors of transcription factors in E. coli. By switching the culture conditions between starvation and growth for 20 hours, we induced strong metabolite concentration changes and accompanying gene expression changes, which were measured by LC-MS/MS and RNA sequencing. From the transcriptome data we calculated the activity of 209 transcriptional regulators with Network Component Analysis, and then tested which metabolites correlated with these activities. This approach captured, for instance, the in vivo Hill-kinetics of CRP regulation by cyclic-AMP, a canonical example of allosteric transcription factor regulation in E. coli. By testing correlations between all pairs of transcription factors and metabolites, we predicted putative effectors of 65 transcription factors, and validated five of them in vitro. These results show that the combination of transcriptomics and metabolomics can generate hypotheses about metabolism-transcription interactions that are relevant in vivo and drive transitions between physiological states.
Project description:The only target locus of transcription factor BglJ known to date is the bgl operon, and activation of bgl by BglJ requires RcsB. Transcription factor LeuO is involved in stress responses and known as antagonist of H-NS. To identifiy novel targets of BglJ, we overexpressed BglJ in Escherichia coli K12 and measured differential gene expression by performing DNA microarray analysis. Moreover, to analyze whether all targets of BglJ require RcsB, we overexpressed BglJ in an rcsB deletion background. In addition, we overexpressed LeuO to identifiy targets of LeuO.
Project description:Metabolism controls gene expression through allosteric interactions between metabolites and transcription factors. These interactions are usually measured with in vitro assays, but there are no methods to identify them at a genome-scale in vivo. Here we show that dynamic transcriptome and metabolome data identify metabolites that control transcription factors in E. coli. By switching an E. coli culture between starvation and growth, we induce strong metabolite concentration changes and gene expression changes. Using Network Component Analysis we calculate the activities of 209 transcriptional regulators and correlate them with metabolites. This approach captures, for instance, the in vivo kinetics of CRP regulation by cyclic-AMP. By testing correlations between all pairs of transcription factors and metabolites, we predict putative effectors of 71 transcription factors, and validate five interactions in vitro. These results show that combining transcriptomics and metabolomics generates hypotheses about metabolism-transcription interactions that drive transitions between physiological states.
Project description:Allosteric regulation is central to the role of the glycolytic enzyme pyruvate kinase M2 (PKM2) in cancer metabolism. Multiple activating and inhibitory allosteric ligands regulate PKM2 activity by controlling the equilibrium between high activity tetramers and low activity dimers and monomers. However, how allosteric inputs from simultaneous binding of different ligands are integrated to regulate PKM2 activity remains elusive. Here, we show that, [PKM2 activation and tetramerisation can be uncoupled as] in the presence of the allosteric inhibitor phenylalanine (Phe), saturating amounts of the activator fructose 1,6-bisphosphate (F-1,6-bP) can induce PKM2 tetramerisation, but fail to maximally increase enzymatic activity. We use a new computational framework to identify residues that mediate FBP-induced allostery and show that, while mutation of A327 and C358 do not abrogate the ability of F-1,6-BP to increase PKM2 activity, it prevents Phe from interfering with it. Our findings demonstrate a role for residues involved in FBP allostery in enabling the integration of allosteric input from Phe and reveal an allosteric cross-talk that underlies the co-ordinate regulation of PKM2 activity by distinct allosteric ligands. The absolute amount of the isoforms of PKM (PKM1/2) were quantified in the cell lines of interested to inform the described model.
Project description:Bacterial transcription factors (TFs) regulate gene expression to adapt to changing environments; when combined, the TF’s regulatory actions comprise transcriptional regulatory networks (TRNs). The chromatin immunoprecipitation (ChIP) assay is the major contemporary method for mapping in vivo protein-DNA interactions in the genome. It enables the genome-wide study of transcription factor binding sites (TFBSs) and gene regulation. Here, we present the genome-wide binding for major TFs in E. coli K-12 MG1655.
Project description:Carboxylic acids are an attractive biorenewable chemical. Enormous progress has been made in engineering microbes for production of these compounds though titers remain lower than desired. Here we used transcriptome analysis of Escherichia coli during exogenous challenge with octanoic acid (C8) at pH 7.0. This analysis suggests that C8 challenge causes intracellular acidification and membrane damage.