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Gao Z, Tang J, Xia J, Zheng CH, Wei PJ. CNNGRN: A Convolutional Neural Network-Based Method for Gene Regulatory Network Inference From Bulk Time-Series Expression Data. IEEE/ACM TRANSACTIONS ON COMPUTATIONAL BIOLOGY AND BIOINFORMATICS 2023; 20:2853-2861. [PMID: 37267145 DOI: 10.1109/tcbb.2023.3282212] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Gene regulatory networks (GRNs) participate in many biological processes, and reconstructing them plays an important role in systems biology. Although many advanced methods have been proposed for GRN reconstruction, their predictive performance is far from the ideal standard, so it is urgent to design a more effective method to reconstruct GRN. Moreover, most methods only consider the gene expression data, ignoring the network structure information contained in GRN. In this study, we propose a supervised model named CNNGRN, which infers GRN from bulk time-series expression data via convolutional neural network (CNN) model, with a more informative feature. Bulk time series gene expression data imply the intricate regulatory associations between genes, and the network structure feature of ground-truth GRN contains rich neighbor information. Hence, CNNGRN integrates the above two features as model inputs. In addition, CNN is adopted to extract intricate features of genes and infer the potential associations between regulators and target genes. Moreover, feature importance visualization experiments are implemented to seek the key features. Experimental results show that CNNGRN achieved competitive performance on benchmark datasets compared to the state-of-the-art computational methods. Finally, hub genes identified based on CNNGRN have been confirmed to be involved in biological processes through literature.
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2
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Sah-Teli SK, Pinkas M, Hynönen MJ, Butcher SJ, Wierenga RK, Novacek J, Venkatesan R. Structural basis for different membrane-binding properties of E. coli anaerobic and human mitochondrial β-oxidation trifunctional enzymes. Structure 2023; 31:812-825.e6. [PMID: 37192613 DOI: 10.1016/j.str.2023.04.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 04/04/2023] [Accepted: 04/20/2023] [Indexed: 05/18/2023]
Abstract
Facultative anaerobic bacteria such as Escherichia coli have two α2β2 heterotetrameric trifunctional enzymes (TFE), catalyzing the last three steps of the β-oxidation cycle: soluble aerobic TFE (EcTFE) and membrane-associated anaerobic TFE (anEcTFE), closely related to the human mitochondrial TFE (HsTFE). The cryo-EM structure of anEcTFE and crystal structures of anEcTFE-α show that the overall assembly of anEcTFE and HsTFE is similar. However, their membrane-binding properties differ considerably. The shorter A5-H7 and H8 regions of anEcTFE-α result in weaker α-β as well as α-membrane interactions, respectively. The protruding H-H region of anEcTFE-β is therefore more critical for membrane-association. Mutational studies also show that this region is important for the stability of the anEcTFE-β dimer and anEcTFE heterotetramer. The fatty acyl tail binding tunnel of the anEcTFE-α hydratase domain, as in HsTFE-α, is wider than in EcTFE-α, accommodating longer fatty acyl tails, in good agreement with their respective substrate specificities.
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Affiliation(s)
- Shiv K Sah-Teli
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, 90220 Oulu, Finland
| | - Matyas Pinkas
- CEITEC Masaryk University, Kamenice 5, 62500 Brno, Czech Republic
| | - Mikko J Hynönen
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, 90220 Oulu, Finland
| | - Sarah J Butcher
- Molecular & Integrative Biosciences Research Programme, Faculty of Biological and Environmental Sciences & Helsinki Institute of Life Science-Institute of Biotechnology, University of Helsinki, 00790 Helsinki, Finland
| | - Rik K Wierenga
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, 90220 Oulu, Finland
| | - Jiri Novacek
- CEITEC Masaryk University, Kamenice 5, 62500 Brno, Czech Republic
| | - Rajaram Venkatesan
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, 90220 Oulu, Finland.
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3
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Park J, Lee SM, Ebrahim A, Scott-Nevros Z, Kim J, Yang L, Sastry A, Seo S, Palsson BO, Kim D. Model-driven experimental design workflow expands understanding of regulatory role of Nac in Escherichia coli. NAR Genom Bioinform 2023; 5:lqad006. [PMID: 36685725 PMCID: PMC9853098 DOI: 10.1093/nargab/lqad006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Revised: 12/07/2022] [Accepted: 01/09/2023] [Indexed: 01/22/2023] Open
Abstract
The establishment of experimental conditions for transcriptional regulator network (TRN) reconstruction in bacteria continues to be impeded by the limited knowledge of activating conditions for transcription factors (TFs). Here, we present a novel genome-scale model-driven workflow for designing experimental conditions, which optimally activate specific TFs. Our model-driven workflow was applied to elucidate transcriptional regulation under nitrogen limitation by Nac and NtrC, in Escherichia coli. We comprehensively predict alternative nitrogen sources, including cytosine and cytidine, which trigger differential activation of Nac using a model-driven workflow. In accordance with the prediction, genome-wide measurements with ChIP-exo and RNA-seq were performed. Integrative data analysis reveals that the Nac and NtrC regulons consist of 97 and 43 genes under alternative nitrogen conditions, respectively. Functional analysis of Nac at the transcriptional level showed that Nac directly down-regulates amino acid biosynthesis and restores expression of tricarboxylic acid (TCA) cycle genes to alleviate nitrogen-limiting stress. We also demonstrate that both TFs coherently modulate α-ketoglutarate accumulation stress due to nitrogen limitation by co-activating amino acid and diamine degradation pathways. A systems-biology approach provided a detailed and quantitative understanding of both TF's roles and how nitrogen and carbon metabolic networks respond complementarily to nitrogen-limiting stress.
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Affiliation(s)
- Joon Young Park
- School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Sang-Mok Lee
- School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Ali Ebrahim
- Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093, USA
| | - Zoe K Scott-Nevros
- School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Jaehyung Kim
- School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Laurence Yang
- Department of Chemical Engineering, Queen's University, Kingston, Canada
| | - Anand Sastry
- Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093, USA
| | - Sang Woo Seo
- School of Chemical and Biological Engineering, and Interdisciplinary Program in Bioengineering, and Institute of Chemical Processes, and Bio-MAX Institute, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Korea
| | - Bernhard O Palsson
- Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093, USA
- Department of Pediatrics, University of California, San Diego, La Jolla, CA 92093, USA
- The Novo Nordisk Foundation Center for Biosustainability, Danish Technical University, 6 Kogle Alle, Hørsholm, Denmark
| | - Donghyuk Kim
- School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
- Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093, USA
- Department of Biomedical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, Republic of Korea
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4
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Gulevich AY, Skorokhodova AY, Debabov VG. Evaluation of the Efficiency of Functional Reversal of Fatty Acid Β-Oxidation in Escherichia coli upon the Action of Various Native Acyl-CoA Dehydrogenases. APPL BIOCHEM MICRO+ 2022. [DOI: 10.1134/s0003683822040196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Abstract
Using Escherichia coli strain MG1655 lacIQ, ∆ackA-pta, ∆poxB, ∆ldhA, ∆adhE, ∆fadE, PL‑SDφ10-atoB, Ptrc-ideal-4-SDφ10-fadB, PL-SDφ10-tesB, ∆yciA as a core strain, the efficiency of the reversal of fatty acid β-oxidation upon the action of native cellular enzymes capable of serving as acyl-CoA dehydrogenases was examined. Increased expression of fadE, fabI, and ydiO/ydiQRST genes encoding the corresponding enzymes was ensured in derivatives of the core strain by substituting their native regulatory regions with artificial regulatory element Ptrc-ideal-4-SDφ10. A three-turn reversal of the cycle in the engineered recombinants was demonstrated that was accompanied by considerable secretion of butyric, caproic, and caprylic acids. The highest level of six- and eight-carbon carboxylates production was achieved upon the overexpression of the fabI gene, while the lowest levels of secretion of the corresponding compounds were demonstrated by the strain with the enhanced expression of the ydiO and ydiQRST genes. The recombinant with the individually enhanced expression of ydiO did not produce detectable amounts of the derivatives of the complete and successful β-oxidation reversal.
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5
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Degradation of Exogenous Fatty Acids in Escherichia coli. Biomolecules 2022; 12:biom12081019. [PMID: 35892328 PMCID: PMC9329746 DOI: 10.3390/biom12081019] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Revised: 07/19/2022] [Accepted: 07/19/2022] [Indexed: 12/10/2022] Open
Abstract
Many bacteria possess all the machineries required to grow on fatty acids (FA) as a unique source of carbon and energy. FA degradation proceeds through the β-oxidation cycle that produces acetyl-CoA and reduced NADH and FADH cofactors. In addition to all the enzymes required for β-oxidation, FA degradation also depends on sophisticated systems for its genetic regulation and for FA transport. The fact that these machineries are conserved in bacteria suggests a crucial role in environmental conditions, especially for enterobacteria. Bacteria also possess specific enzymes required for the degradation of FAs from their environment, again showing the importance of this metabolism for bacterial adaptation. In this review, we mainly describe FA degradation in the Escherichia coli model, and along the way, we highlight and discuss important aspects of this metabolism that are still unclear. We do not detail exhaustively the diversity of the machineries found in other bacteria, but we mention them if they bring additional information or enlightenment on specific aspects.
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6
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Ma X, Ma L, Huo YX. Reconstructing the transcription regulatory network to optimize resource allocation for robust biosynthesis. Trends Biotechnol 2021; 40:735-751. [PMID: 34895933 DOI: 10.1016/j.tibtech.2021.11.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2021] [Revised: 11/07/2021] [Accepted: 11/08/2021] [Indexed: 11/16/2022]
Abstract
An ideal microbial cell factory (MCF) should deliver maximal resources to production, which conflicts with the microbe's native growth-oriented resource allocation strategy and can therefore lead to early termination of the high-yield period. Reallocating resources from growth to production has become a critical factor in constructing robust MCFs. Instead of strengthening specific biosynthetic pathways, emerging endeavors are focused on rearranging the gene regulatory network to fundamentally reprogram the resource allocation pattern. Combining this idea with transcriptional regulation within the hierarchical regulatory network, this review discusses recent engineering strategies targeting the transcription machinery, module networks, regulatory edges, and bottom network layer. This global view will help to construct a production-oriented phenotype that fully harnesses the potential of MCFs.
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Affiliation(s)
- Xiaoyan Ma
- Key Laboratory of Molecular Medicine and Biotherapy, School of Life Science, Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, Beijing 100081, People's Republic of China
| | - Lianjie Ma
- Key Laboratory of Molecular Medicine and Biotherapy, School of Life Science, Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, Beijing 100081, People's Republic of China
| | - Yi-Xin Huo
- Key Laboratory of Molecular Medicine and Biotherapy, School of Life Science, Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, Beijing 100081, People's Republic of China; Tobacco Research Institute, Chinese Academy of Agricultural Sciences, Qingdao 266101, People's Republic of China.
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7
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Price EE, Román-Rodríguez F, Boyd JM. Bacterial approaches to sensing and responding to respiration and respiration metabolites. Mol Microbiol 2021; 116:1009-1021. [PMID: 34387370 DOI: 10.1111/mmi.14795] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 08/03/2021] [Accepted: 08/09/2021] [Indexed: 11/29/2022]
Abstract
Bacterial respiration of diverse substrates is a primary contributor to the diversity of life. Respiration also drives alterations in the geosphere and tethers ecological nodes together. It provides organisms with a means to dissipate reductants and generate potential energy in the form of an electrochemical gradient. Mechanisms have evolved to sense flux through respiratory pathways and sense the altered concentrations of respiration substrates or byproducts. These genetic regulatory systems promote efficient utilization of respiration substrates, as well as fine tune metabolism to promote cellular fitness and negate the accumulation of toxic byproducts. Many bacteria can respire one or more chemicals, and these regulatory systems promote the prioritization of high energy metabolites. Herein we focus on regulatory paradigms and discuss systems that sense the concentrations of respiration substrates and flux through respiratory pathways. This is a broad field of study, and therefore we focus on key fundamental and recent developments and highlight specific systems that capture the diversity of sensing mechanisms.
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Affiliation(s)
- Erin E Price
- Department of Biochemistry & Microbiology, Rutgers, The State University of New Jersey, New Brunswick, NJ, 08901, USA
| | - Franklin Román-Rodríguez
- Department of Biochemistry & Microbiology, Rutgers, The State University of New Jersey, New Brunswick, NJ, 08901, USA
| | - Jeffrey M Boyd
- Department of Biochemistry & Microbiology, Rutgers, The State University of New Jersey, New Brunswick, NJ, 08901, USA
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8
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Jaswal K, Shrivastava M, Chaba R. Revisiting long-chain fatty acid metabolism in Escherichia coli: integration with stress responses. Curr Genet 2021; 67:573-582. [PMID: 33740112 DOI: 10.1007/s00294-021-01178-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 03/09/2021] [Accepted: 03/11/2021] [Indexed: 12/29/2022]
Abstract
Long-chain fatty acids (LCFAs) are a tremendous source of metabolic energy, an essential component of membranes, and important effector molecules that regulate a myriad of cellular processes. As an energy-rich nutrient source, the role of LCFAs in promoting bacterial survival and infectivity is well appreciated. LCFA degradation generates a large number of reduced cofactors that may confer redox stress; therefore, it is imperative to understand how bacteria deal with this paradoxical situation. Although the LCFA utilization pathway has been studied in great detail, especially in Escherichia coli, where the earliest studies date back to the 1960s, the interconnection of LCFA degradation with bacterial stress responses remained largely unexplored. Recent work in E. coli shows that LCFA degradation induces oxidative stress and also impedes oxidative protein folding. Importantly, both issues arise due to the insufficiency of ubiquinone, a lipid-soluble electron carrier in the electron transport chain. However, to maintain redox homeostasis, bacteria induce sophisticated cellular responses. Here, we review these findings in light of our current knowledge of the LCFA metabolic pathway, metabolism-induced oxidative stress, the process of oxidative protein folding, and stress combat mechanisms. We discuss probable mechanisms for the activation of defense players during LCFA metabolism and the likely feedback imparted by them. We suggest that besides defending against intrinsic stresses, LCFA-mediated upregulation of stress response pathways primes bacteria to adapt to harsh external environments. Collectively, the interplay between LCFA metabolism and stress responses is likely an important factor that underlies the success of LCFA-utilizing bacteria in the host.
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Affiliation(s)
- Kanchan Jaswal
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, SAS Nagar, Punjab, India
| | - Megha Shrivastava
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, SAS Nagar, Punjab, India
| | - Rachna Chaba
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, SAS Nagar, Punjab, India.
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9
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The Canonical Long-Chain Fatty Acid Sensing Machinery Processes Arachidonic Acid To Inhibit Virulence in Enterohemorrhagic Escherichia coli. mBio 2021; 12:mBio.03247-20. [PMID: 33468701 PMCID: PMC7845647 DOI: 10.1128/mbio.03247-20] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Polyunsaturated fatty acids (PUFAs) play important roles in host immunity. Manipulation of lipid content in host tissues through diet or pharmacological interventions is associated with altered severity of various inflammatory diseases. The mammalian gastrointestinal tract is a complex biochemical organ that generates a diverse milieu of host- and microbe-derived metabolites. In this environment, bacterial pathogens sense and respond to specific stimuli, which are integrated into the regulation of their virulence programs. Previously, we identified the transcription factor FadR, a long-chain fatty acid (LCFA) acyl coenzyme A (acyl-CoA) sensor, as a novel virulence regulator in the human foodborne pathogen enterohemorrhagic Escherichia coli (EHEC). Here, we demonstrate that exogenous LCFAs directly inhibit the locus of enterocyte effacement (LEE) pathogenicity island in EHEC through sensing by FadR. Moreover, in addition to LCFAs that are 18 carbons in length or shorter, we introduce host-derived arachidonic acid (C20:4) as an additional LCFA that is recognized by the FadR system in EHEC. We show that arachidonic acid is processed by the acyl-CoA synthetase FadD, which permits binding to FadR and decreases FadR affinity for its target DNA sequences. This interaction enables the transcriptional regulation of FadR-responsive operons by arachidonic acid in EHEC, including the LEE. Finally, we show that arachidonic acid inhibits hallmarks of EHEC disease in a FadR-dependent manner, including EHEC attachment to epithelial cells and the formation of attaching and effacing lesions. Together, our findings delineate a molecular mechanism demonstrating how LCFAs can directly inhibit the virulence of an enteric bacterial pathogen. More broadly, our findings expand the repertoire of ligands sensed by the canonical LFCA sensing machinery in EHEC to include arachidonic acid, an important bioactive lipid that is ubiquitous within host environments.
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10
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Sah-Teli SK, Hynönen MJ, Sulu R, Dalwani S, Schmitz W, Wierenga RK, Venkatesan R. Insights into the stability and substrate specificity of the E. coli aerobic β-oxidation trifunctional enzyme complex. J Struct Biol 2020; 210:107494. [DOI: 10.1016/j.jsb.2020.107494] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Revised: 03/09/2020] [Accepted: 03/10/2020] [Indexed: 11/17/2022]
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11
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Complementary substrate specificity and distinct quaternary assembly of the Escherichia coli aerobic and anaerobic β-oxidation trifunctional enzyme complexes. Biochem J 2019; 476:1975-1994. [DOI: 10.1042/bcj20190314] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Revised: 06/20/2019] [Accepted: 06/24/2019] [Indexed: 02/03/2023]
Abstract
AbstractThe trifunctional enzyme (TFE) catalyzes the last three steps of the fatty acid β-oxidation cycle. Two TFEs are present in Escherichia coli, EcTFE and anEcTFE. EcTFE is expressed only under aerobic conditions, whereas anEcTFE is expressed also under anaerobic conditions, with nitrate or fumarate as the ultimate electron acceptor. The anEcTFE subunits have higher sequence identity with the human mitochondrial TFE (HsTFE) than with the soluble EcTFE. Like HsTFE, here it is found that anEcTFE is a membrane-bound complex. Systematic enzyme kinetic studies show that anEcTFE has a preference for medium- and long-chain enoyl-CoAs, similar to HsTFE, whereas EcTFE prefers short chain enoyl-CoA substrates. The biophysical characterization of anEcTFE and EcTFE shows that EcTFE is heterotetrameric, whereas anEcTFE is purified as a complex of two heterotetrameric units, like HsTFE. The tetrameric assembly of anEcTFE resembles the HsTFE tetramer, although the arrangement of the two anEcTFE tetramers in the octamer is different from the HsTFE octamer. These studies demonstrate that EcTFE and anEcTFE have complementary substrate specificities, allowing for complete degradation of long-chain enoyl-CoAs under aerobic conditions. The new data agree with the notion that anEcTFE and HsTFE are evolutionary closely related, whereas EcTFE belongs to a separate subfamily.
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12
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Microbial Production of Fatty Acid via Metabolic Engineering and Synthetic Biology. BIOTECHNOL BIOPROC E 2019. [DOI: 10.1007/s12257-018-0374-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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13
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Xiong X, Bales ES, Ir D, Robertson CE, McManaman JL, Frank DN, Parkinson J. Perilipin-2 modulates dietary fat-induced microbial global gene expression profiles in the mouse intestine. MICROBIOME 2017; 5:117. [PMID: 28877764 PMCID: PMC5588750 DOI: 10.1186/s40168-017-0327-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Accepted: 08/20/2017] [Indexed: 05/06/2023]
Abstract
BACKGROUND Intestinal microbiota are critical determinants of obesity and metabolic disease risk. In previous work, we showed that deletion of the cytoplasmic lipid droplet (CLD) protein perilipin-2 (Plin2) modulates gut microbial community structure and abrogates long-term deleterious effects of a high-fat (HF) diet in mice. However, the impact of Plin2 on microbiome function is unknown. RESULTS Here, we used metatranscriptomics to identify differences in microbiome transcript expression in WT and Plin2-null mice following acute exposure to high-fat/low-carbohydrate (HF) or low-fat/high-carbohydrate (LF) diets. Consistent with previous studies, dietary changes resulted in significant taxonomic shifts. Unexpectedly, when fed a HF diet, the microbiota of Plin2-null and WT mice exhibited dramatic shifts in transcript expression despite no discernible shift in community structure. For Plin2-null mice, these changes included the coordinated upregulation of metabolic enzymes directing flux towards the production of growth metabolites such as fatty acids, nucleotides, and amino acids. In contrast, the LF diet did not appear to induce the same dramatic changes in transcript or pathway expression between the two genotypes. CONCLUSIONS Our data shows that a host genotype can modulate microbiome function without impacting community structure and identify Plin2 as a specific host determinant of diet effects on microbial function. Along with uncovering potential mechanisms for integrating how diet modulates host and microbial metabolism, our findings demonstrate the limits of 16S rRNA surveys to inform on community functional activities and the need to prioritize metatranscriptomic studies to gain more meaningful insights into microbiome function.
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Affiliation(s)
- Xuejian Xiong
- Molecular Medicine, Hospital for Sick Children, 686 Bay Street, Toronto, M5G 0A4 ON Canada
| | - Elise S. Bales
- Division of Reproductive Sciences, University of Colorado, 12700 E. 19th Avenue, Aurora, 80045 CO USA
| | - Diana Ir
- Division of Infectious Diseases, University of Colorado, 12700 E. 19th Avenue, Aurora, 80045 CO USA
| | - Charles E. Robertson
- Division of Infectious Diseases, University of Colorado, 12700 E. 19th Avenue, Aurora, 80045 CO USA
- Microbiome Research Consortium, University of Colorado, 12700 E. 19th Avenue, Aurora, 80045 CO USA
| | - James L. McManaman
- Division of Reproductive Sciences, University of Colorado, 12700 E. 19th Avenue, Aurora, 80045 CO USA
- The Center for Human Nutrition, University of Colorado, 12700 E. 19th Avenue, Aurora, 80045 CO USA
| | - Daniel N. Frank
- Division of Infectious Diseases, University of Colorado, 12700 E. 19th Avenue, Aurora, 80045 CO USA
- Microbiome Research Consortium, University of Colorado, 12700 E. 19th Avenue, Aurora, 80045 CO USA
| | - John Parkinson
- Molecular Medicine, Hospital for Sick Children, 686 Bay Street, Toronto, M5G 0A4 ON Canada
- Department of Molecular Genetics, University of Toronto, 1 King’s College Circle, Toronto, M5S 1A8 ON Canada
- Department of Biochemistry, University of Toronto, 1 King’s College Circle, Toronto, M5S 1A8 ON Canada
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14
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Consuegra J, Plucain J, Gaffé J, Hindré T, Schneider D. Genetic Basis of Exploiting Ecological Opportunity During the Long-Term Diversification of a Bacterial Population. J Mol Evol 2017; 85:26-36. [PMID: 28744786 DOI: 10.1007/s00239-017-9802-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Accepted: 07/15/2017] [Indexed: 11/25/2022]
Abstract
Adaptive diversification is an essential evolutionary process, one that produces phenotypic innovations including the colonization of available ecological niches. Bacteria can diverge in sympatry when ecological opportunities allow, but the underlying genetic mechanisms are often unknown. Perhaps, the longest-lasting adaptive diversification seen in the laboratory occurred during the long-term evolution experiment, in which 12 populations of Escherichia coli have been evolving independently for more than 65,000 generations from a common ancestor. In one population, two lineages, S and L, emerged at ~6500 generations and have dynamically coexisted ever since by negative frequency-dependent interactions mediated, in part, by acetate secretion by L. Mutations in spoT, arcA, and gntR promoted the emergence of the S lineage, although they reproduced only partially its phenotypic traits. Here, we characterize the evolved mechanism of acetate consumption by the S lineage that enabled invasion and coexistence with the L lineage. We identified an additional mutation in acs that, together with the arcA mutation, drove an early restructuring of the transcriptional control of central metabolism in S, leading to improved acetate consumption. Pervasive epistatic interactions within the S genome contributed to the exploitation of this new ecological opportunity. The emergence and maintenance of this long-term polymorphism is a complex multi-step process.
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Affiliation(s)
- Jessika Consuegra
- University of Grenoble Alpes, CNRS, Grenoble INP, TIMC-IMAG, 38000, Grenoble, France
| | - Jessica Plucain
- University of Grenoble Alpes, CNRS, Grenoble INP, TIMC-IMAG, 38000, Grenoble, France
| | - Joël Gaffé
- University of Grenoble Alpes, CNRS, Grenoble INP, TIMC-IMAG, 38000, Grenoble, France
| | - Thomas Hindré
- University of Grenoble Alpes, CNRS, Grenoble INP, TIMC-IMAG, 38000, Grenoble, France.
| | - Dominique Schneider
- University of Grenoble Alpes, CNRS, Grenoble INP, TIMC-IMAG, 38000, Grenoble, France
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15
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Metabolic engineering of Corynebacterium crenatium for enhancing production of higher alcohols. Sci Rep 2016; 6:39543. [PMID: 27996038 PMCID: PMC5172369 DOI: 10.1038/srep39543] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Accepted: 11/24/2016] [Indexed: 12/19/2022] Open
Abstract
Biosynthesis approaches for the production of higher alcohols as a source of alternative fossil fuels have garnered increasing interest recently. However, there is little information available in the literature about using undirected whole-cell mutagenesis (UWCM) in vivo to improve higher alcohols production. In this study, for the first time, we approached this question from two aspects: first preferentially improving the capacity of expression host, and subsequently optimizing metabolic pathways using multiple genetic mutations to shift metabolic flux toward the biosynthetic pathway of target products to convert intermediate 2-keto acid compounds into diversified C4~C5 higher alcohols using UWCM in vivo, with the aim of improving the production. The results demonstrated the production of higher alcohols including isobutanol, 2-methyl-1-butanol, 3-methyl-1-butanol from glucose and duckweed under simultaneous saccharification and fermentation (SSF) scheme were higher based on the two aspects compared with only the use of wild-type stain as expression host. These findings showed that the improvement via UWCM in vivo in the two aspects for expression host and metabolic flux can facilitate the increase of higher alcohols production before using gene editing technology. Our work demonstrates that a multi-faceted approach for the engineering of novel synthetic pathways in microorganisms for improving biofuel production is feasible.
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16
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Scheel RA, Ji L, Lundgren BR, Nomura CT. Enhancing poly(3-hydroxyalkanoate) production in Escherichia coli by the removal of the regulatory gene arcA. AMB Express 2016; 6:120. [PMID: 27878786 PMCID: PMC5120623 DOI: 10.1186/s13568-016-0291-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Accepted: 11/09/2016] [Indexed: 11/18/2022] Open
Abstract
Recombinant Escherichia coli is a desirable platform for the production of many biological compounds including poly(3-hydroxyalkanoates), a class of naturally occurring biodegradable polyesters with promising biomedical and material applications. Although the controlled production of desirable polymers is possible with the utilization of fatty acid feedstocks, a central challenge to this biosynthetic route is the improvement of the relatively low polymer yield, a necessary factor of decreasing the production costs. In this study we sought to address this challenge by deleting arcA and ompR, two global regulators with the capacity to inhibit the uptake and activation of exogenous fatty acids. We found that polymer yields in a ΔarcA mutant increased significantly with respect to the parental strain. In the parental strain, PHV yields were very low but improved 64-fold in the ΔarcA mutant (1.92-124 mg L-1) The ΔarcA mutant also allowed for modest increases in some medium chain length polymer yields, while weight average molecular weights improved by approximately 1.5-fold to 12-fold depending on the fatty acid substrate utilized. These results were supported by an analysis of differential gene expression, which showed that the key genes (fadD, fadL, and fadE) encoding fatty acid degradation enzymes were all upregulated by 2-, 10-, and 31-fold in an ΔarcA mutant, respectively. Additionally, the short chain length fatty acid uptake genes atoA, atoE and atoD were upregulated by 103-, 119-, and 303-fold respectively, though these values are somewhat inflated due to low expression in the parental strain. Overall, this study demonstrates that arcA is an important target to improve PHA production from fatty acids.
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Affiliation(s)
- Ryan A. Scheel
- Department of Chemistry, State University of New York College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, NY 13210 USA
| | - Liyuan Ji
- Department of Chemistry, State University of New York College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, NY 13210 USA
| | - Benjamin R. Lundgren
- Department of Chemistry, State University of New York College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, NY 13210 USA
| | - Christopher T. Nomura
- Department of Chemistry, State University of New York College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, NY 13210 USA
- Center for Applied Microbiology, State University of New York College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, NY 13210 USA
- Hubei Collaborative Center for Green Transformation of Bio-Resources, College of Life Sciences, Hubei University, Wuhan, 430062 China
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17
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Gulevich AY, Skorokhodova AY, Debabov VG. Escherichia coli ydiO and ydiQRST genes encode components of acyl-CoA dehydrogenase complex of anaerobic fatty acid β-oxidation pathway. RUSS J GENET+ 2016. [DOI: 10.1134/s1022795416100021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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18
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Reconstruction and Use of Microbial Metabolic Networks: the Core Escherichia coli Metabolic Model as an Educational Guide. EcoSal Plus 2015; 4. [PMID: 26443778 DOI: 10.1128/ecosalplus.10.2.1] [Citation(s) in RCA: 138] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Biochemical network reconstructions have become popular tools in systems biology. Metabolicnetwork reconstructions are biochemically, genetically, and genomically (BiGG) structured databases of biochemical reactions and metabolites. They contain information such as exact reaction stoichiometry, reaction reversibility, and the relationships between genes, proteins, and reactions. Network reconstructions have been used extensively to study the phenotypic behavior of wild-type and mutant stains under a variety of conditions, linking genotypes with phenotypes. Such phenotypic simulations have allowed for the prediction of growth after genetic manipulations, prediction of growth phenotypes after adaptive evolution, and prediction of essential genes. Additionally, because network reconstructions are organism specific, they can be used to understand differences between organisms of species in a functional context.There are different types of reconstructions representing various types of biological networks (metabolic, regulatory, transcription/translation). This chapter serves as an introduction to metabolic and regulatory network reconstructions and models and gives a complete description of the core Escherichia coli metabolic model. This model can be analyzed in any computational format (such as MATLAB or Mathematica) based on the information given in this chapter. The core E. coli model is a small-scale model that can be used for educational purposes. It is meant to be used by senior undergraduate and first-year graduate students learning about constraint-based modeling and systems biology. This model has enough reactions and pathways to enable interesting and insightful calculations, but it is also simple enough that the results of such calculations can be understoodeasily.
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Sathesh-Prabu C, Lee SK. Production of Long-Chain α,ω-Dicarboxylic Acids by Engineered Escherichia coli from Renewable Fatty Acids and Plant Oils. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2015; 63:8199-8208. [PMID: 26359801 DOI: 10.1021/acs.jafc.5b03833] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Long-chain α,ω-dicarboxylic acids (LDCAs, ≥ C12) are widely used as a raw material for preparing various commodities and polymers. In this study, a CYP450-monooxygenase-mediated ω-oxidation pathway system with high ω-regioselectivity was heterologously expressed in Escherichia coli to produce DCAs from fatty acids. The resulting engineered E. coli produced a maximum of 41 mg/L of C12 DCA and 163 mg/L of C14 DCA from fatty acids (1 g/L), following 20 h of whole cell biotransformation. Addition of a heme precursor and the hydroxyl radical scavenger, thiourea, increased product concentration (159 mg/L of C12 DCA and 410 mg/L of C14 DCA) in a shorter culture duration than that of the corresponding controls. DCAs of various chain lengths were synthesized from coconut oil hydrolysate using the engineered E. coli. This novel synthetic biocatalytic system could be applied to produce high value DCAs in a cost-effective manner from renewable plant oils.
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Affiliation(s)
- Chandran Sathesh-Prabu
- School of Energy and Chemical Engineering, and ‡School of Life Sciences, Ulsan National Institute of Science and Technology (UNIST) , Ulsan 689-798, Republic of Korea
| | - Sung Kuk Lee
- School of Energy and Chemical Engineering, and ‡School of Life Sciences, Ulsan National Institute of Science and Technology (UNIST) , Ulsan 689-798, Republic of Korea
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20
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Khodayari A, Chowdhury A, Maranas CD. Succinate Overproduction: A Case Study of Computational Strain Design Using a Comprehensive Escherichia coli Kinetic Model. Front Bioeng Biotechnol 2015; 2:76. [PMID: 25601910 PMCID: PMC4283520 DOI: 10.3389/fbioe.2014.00076] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Accepted: 12/05/2014] [Indexed: 01/25/2023] Open
Abstract
Computational strain-design prediction accuracy has been the focus for many recent efforts through the selective integration of kinetic information into metabolic models. In general, kinetic model prediction quality is determined by the range and scope of genetic and/or environmental perturbations used during parameterization. In this effort, we apply the k-OptForce procedure on a kinetic model of E. coli core metabolism constructed using the Ensemble Modeling (EM) method and parameterized using multiple mutant strains data under aerobic respiration with glucose as the carbon source. Minimal interventions are identified that improve succinate yield under both aerobic and anaerobic conditions to test the fidelity of model predictions under both genetic and environmental perturbations. Under aerobic condition, k-OptForce identifies interventions that match existing experimental strategies while pointing at a number of unexplored flux re-directions such as routing glyoxylate flux through the glycerate metabolism to improve succinate yield. Many of the identified interventions rely on the kinetic descriptions that would not be discoverable by a purely stoichiometric description. In contrast, under fermentative (anaerobic) condition, k-OptForce fails to identify key interventions including up-regulation of anaplerotic reactions and elimination of competitive fermentative products. This is due to the fact that the pathways activated under anaerobic condition were not properly parameterized as only aerobic flux data were used in the model construction. This study shed light on the importance of condition-specific model parameterization and provides insight on how to augment kinetic models so as to correctly respond to multiple environmental perturbations.
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Affiliation(s)
- Ali Khodayari
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, USA
| | - Anupam Chowdhury
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, USA
| | - Costas D. Maranas
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, USA
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21
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Siedler S, Bringer S, Polen T, Bott M. NADPH-dependent reductive biotransformation with Escherichia coli and its pfkA deletion mutant: influence on global gene expression and role of oxygen supply. Biotechnol Bioeng 2014; 111:2067-75. [PMID: 24771245 DOI: 10.1002/bit.25271] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Revised: 02/25/2014] [Accepted: 04/14/2014] [Indexed: 11/11/2022]
Abstract
An Escherichia coli ΔpfkA mutant lacking the major phosphofructokinase possesses a partially cyclized pentose phosphate pathway leading to an increased NADPH per glucose ratio. This effect decreases the amount of glucose required for NADPH regeneration in reductive biotransformations, such as the conversion of methyl acetoacetate (MAA) to (R)-methyl 3-hydroxybutyrate (MHB) by an alcohol dehydrogenase from Lactobacillus brevis. Here, global transcriptional analyses were performed to study regulatory responses during reductive biotransformation. DNA microarray analysis revealed amongst other things increased expression of soxS, supporting previous results indicating that a high NADPH demand contributes to the activation of SoxR, the transcriptional activator of soxS. Furthermore, several target genes of the ArcAB two-component system showed a lower mRNA level in the reference strain than in the ΔpfkA mutant, pointing to an increased QH2 /Q ratio in the reference strain. This prompted us to analyze yields and productivities of MAA reduction to MHB under different oxygen regimes in a bioreactor. Under anaerobic conditions, the specific MHB production rates of both strains were comparable (7.4 ± 0.2 mmolMHB h(-1) gcdw (-1) ) and lower than under conditions of 15% dissolved oxygen, where those of the reference strain (12.8 mmol h(-1) gcdw (-1) ) and of the ΔpfkA mutant (11.0 mmol h(-1) gcdw (-1) ) were 73% and 49% higher. While the oxygen transfer rate (OTR) of the reference strain increased after the addition of MAA, presumably due to the oxidation of the acetate accumulated before MAA addition, the OTR of the ΔpfkA strain strongly decreased, indicating a very low respiration rate despite sufficient oxygen supply. The latter effect can likely be attributed to a restricted conversion of NADPH into NADH via the soluble transhydrogenase SthA, as the enzyme is outcompeted in the presence of MAA by the recombinant NADPH-dependent alcohol dehydrogenase. The differences in respiration rates can explain the suggested higher ArcAB activity in the reference strain.
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Affiliation(s)
- Solvej Siedler
- Institut für Bio- und Geowissenschaften, IBG-1: Biotechnologie, Forschungszentrum Jülich, D-52425, Jülich, Germany
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22
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SearchDOGS bacteria, software that provides automated identification of potentially missed genes in annotated bacterial genomes. J Bacteriol 2014; 196:2030-42. [PMID: 24659774 DOI: 10.1128/jb.01368-13] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
We report the development of SearchDOGS Bacteria, software to automatically detect missing genes in annotated bacterial genomes by combining BLAST searches with comparative genomics. Having successfully applied the approach to yeast genomes, we redeveloped SearchDOGS to function as a standalone, downloadable package, requiring only a set of GenBank annotation files as input. The software automatically generates a homology structure using reciprocal BLAST and a synteny-based method; this is followed by a scan of the entire genome of each species for unannotated genes. Results are provided in a HTML interface, providing coordinates, BLAST results, syntenic location, omega values (Ka/Ks, where Ks is the number of synonymous substitutions per synonymous site and Ka is the number of nonsynonymous substitutions per nonsynonymous site) for protein conservation estimates, and other information for each candidate gene. Using SearchDOGS Bacteria, we identified 155 gene candidates in the Shigella boydii sb227 genome, including 56 candidates of length < 60 codons. SearchDOGS Bacteria has two major advantages over currently available annotation software. First, it outperforms current methods in terms of sensitivity and is highly effective at identifying small or highly diverged genes. Second, as a freely downloadable package, it can be used with unpublished or confidential data.
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23
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The highly conserved MraZ protein is a transcriptional regulator in Escherichia coli. J Bacteriol 2014; 196:2053-66. [PMID: 24659771 DOI: 10.1128/jb.01370-13] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The mraZ and mraW genes are highly conserved in bacteria, both in sequence and in their position at the head of the division and cell wall (dcw) gene cluster. Located directly upstream of the mraZ gene, the Pmra promoter drives the transcription of mraZ and mraW, as well as many essential cell division and cell wall genes, but no regulator of Pmra has been found to date. Although MraZ has structural similarity to the AbrB transition state regulator and the MazE antitoxin and MraW is known to methylate the 16S rRNA, mraZ and mraW null mutants have no detectable phenotypes. Here we show that overproduction of Escherichia coli MraZ inhibited cell division and was lethal in rich medium at high induction levels and in minimal medium at low induction levels. Co-overproduction of MraW suppressed MraZ toxicity, and loss of MraW enhanced MraZ toxicity, suggesting that MraZ and MraW have antagonistic functions. MraZ-green fluorescent protein localized to the nucleoid, suggesting that it binds DNA. Consistent with this idea, purified MraZ directly bound a region of DNA containing three direct repeats between Pmra and the mraZ gene. Excess MraZ reduced the expression of an mraZ-lacZ reporter, suggesting that MraZ acts as a repressor of Pmra, whereas a DNA-binding mutant form of MraZ failed to repress expression. Transcriptome sequencing (RNA-seq) analysis suggested that MraZ also regulates the expression of genes outside the dcw cluster. In support of this, purified MraZ could directly bind to a putative operator site upstream of mioC, one of the repressed genes identified by RNA-seq.
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24
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Janßen HJ, Steinbüchel A. Fatty acid synthesis in Escherichia coli and its applications towards the production of fatty acid based biofuels. BIOTECHNOLOGY FOR BIOFUELS 2014; 7:7. [PMID: 24405789 PMCID: PMC3896788 DOI: 10.1186/1754-6834-7-7] [Citation(s) in RCA: 181] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Accepted: 12/24/2013] [Indexed: 05/04/2023]
Abstract
The idea of renewable and regenerative resources has inspired research for more than a hundred years. Ideally, the only spent energy will replenish itself, like plant material, sunlight, thermal energy or wind. Biodiesel or ethanol are examples, since their production relies mainly on plant material. However, it has become apparent that crop derived biofuels will not be sufficient to satisfy future energy demands. Thus, especially in the last decade a lot of research has focused on the production of next generation biofuels. A major subject of these investigations has been the microbial fatty acid biosynthesis with the aim to produce fatty acids or derivatives for substitution of diesel. As an industrially important organism and with the best studied microbial fatty acid biosynthesis, Escherichia coli has been chosen as producer in many of these studies and several reviews have been published in the fields of E. coli fatty acid biosynthesis or biofuels. However, most reviews discuss only one of these topics in detail, despite the fact, that a profound understanding of the involved enzymes and their regulation is necessary for efficient genetic engineering of the entire pathway. The first part of this review aims at summarizing the knowledge about fatty acid biosynthesis of E. coli and its regulation, and it provides the connection towards the production of fatty acids and related biofuels. The second part gives an overview about the achievements by genetic engineering of the fatty acid biosynthesis towards the production of next generation biofuels. Finally, the actual importance and potential of fatty acid-based biofuels will be discussed.
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Affiliation(s)
- Helge Jans Janßen
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, Corrensstrasse 3, D-48149, Münster, Germany
| | - Alexander Steinbüchel
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, Corrensstrasse 3, D-48149, Münster, Germany
- Environmental Sciences Department, King Abdulaziz University, Jeddah, Saudi Arabia
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25
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Park DM, Akhtar MS, Ansari AZ, Landick R, Kiley PJ. The bacterial response regulator ArcA uses a diverse binding site architecture to regulate carbon oxidation globally. PLoS Genet 2013; 9:e1003839. [PMID: 24146625 PMCID: PMC3798270 DOI: 10.1371/journal.pgen.1003839] [Citation(s) in RCA: 104] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 08/13/2013] [Indexed: 12/02/2022] Open
Abstract
Despite the importance of maintaining redox homeostasis for cellular viability, how cells control redox balance globally is poorly understood. Here we provide new mechanistic insight into how the balance between reduced and oxidized electron carriers is regulated at the level of gene expression by mapping the regulon of the response regulator ArcA from Escherichia coli, which responds to the quinone/quinol redox couple via its membrane-bound sensor kinase, ArcB. Our genome-wide analysis reveals that ArcA reprograms metabolism under anaerobic conditions such that carbon oxidation pathways that recycle redox carriers via respiration are transcriptionally repressed by ArcA. We propose that this strategy favors use of catabolic pathways that recycle redox carriers via fermentation akin to lactate production in mammalian cells. Unexpectedly, bioinformatic analysis of the sequences bound by ArcA in ChIP-seq revealed that most ArcA binding sites contain additional direct repeat elements beyond the two required for binding an ArcA dimer. DNase I footprinting assays suggest that non-canonical arrangements of cis-regulatory modules dictate both the length and concentration-sensitive occupancy of DNA sites. We propose that this plasticity in ArcA binding site architecture provides both an efficient means of encoding binding sites for ArcA, σ(70)-RNAP and perhaps other transcription factors within the same narrow sequence space and an effective mechanism for global control of carbon metabolism to maintain redox homeostasis.
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Affiliation(s)
- Dan M. Park
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Md. Sohail Akhtar
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Aseem Z. Ansari
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Robert Landick
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Department of Bacteriology; University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Patricia J. Kiley
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
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26
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O’Brien EJ, Lerman JA, Chang RL, Hyduke DR, Palsson BØ. Genome-scale models of metabolism and gene expression extend and refine growth phenotype prediction. Mol Syst Biol 2013; 9:693. [PMID: 24084808 PMCID: PMC3817402 DOI: 10.1038/msb.2013.52] [Citation(s) in RCA: 309] [Impact Index Per Article: 28.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Accepted: 09/05/2013] [Indexed: 12/18/2022] Open
Abstract
Growth is a fundamental process of life. Growth requirements are well-characterized experimentally for many microbes; however, we lack a unified model for cellular growth. Such a model must be predictive of events at the molecular scale and capable of explaining the high-level behavior of the cell as a whole. Here, we construct an ME-Model for Escherichia coli--a genome-scale model that seamlessly integrates metabolic and gene product expression pathways. The model computes ~80% of the functional proteome (by mass), which is used by the cell to support growth under a given condition. Metabolism and gene expression are interdependent processes that affect and constrain each other. We formalize these constraints and apply the principle of growth optimization to enable the accurate prediction of multi-scale phenotypes, ranging from coarse-grained (growth rate, nutrient uptake, by-product secretion) to fine-grained (metabolic fluxes, gene expression levels). Our results unify many existing principles developed to describe bacterial growth.
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Affiliation(s)
- Edward J O’Brien
- Department of Bioengineering, University of California San Diego, La Jolla, CA, USA
| | - Joshua A Lerman
- Department of Bioengineering, University of California San Diego, La Jolla, CA, USA
| | - Roger L Chang
- Department of Bioengineering, University of California San Diego, La Jolla, CA, USA
| | - Daniel R Hyduke
- Department of Bioengineering, University of California San Diego, La Jolla, CA, USA
| | - Bernhard Ø Palsson
- Department of Bioengineering, University of California San Diego, La Jolla, CA, USA
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27
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Ma Q, Liu B, Zhou C, Yin Y, Li G, Xu Y. An integrated toolkit for accurate prediction and analysis of cis-regulatory motifs at a genome scale. ACTA ACUST UNITED AC 2013; 29:2261-8. [PMID: 23846744 DOI: 10.1093/bioinformatics/btt397] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
MOTIVATION We present an integrated toolkit, BoBro2.0, for prediction and analysis of cis-regulatory motifs. This toolkit can (i) reliably identify statistically significant cis-regulatory motifs at a genome scale; (ii) accurately scan for all motif instances of a query motif in specified genomic regions using a novel method for P-value estimation; (iii) provide highly reliable comparisons and clustering of identified motifs, which takes into consideration the weak signals from the flanking regions of the motifs; and (iv) analyze co-occurring motifs in the regulatory regions. RESULTS We have carried out systematic comparisons between motif predictions using BoBro2.0 and the MEME package. The comparison results on Escherichia coli K12 genome and the human genome show that BoBro2.0 can identify the statistically significant motifs at a genome scale more efficiently, identify motif instances more accurately and get more reliable motif clusters than MEME. In addition, BoBro2.0 provides correlational analyses among the identified motifs to facilitate the inference of joint regulation relationships of transcription factors. AVAILABILITY The source code of the program is freely available for noncommercial uses at http://code.google.com/p/bobro/. CONTACT xyn@bmb.uga.edu SUPPLEMENTARY INFORMATION Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Qin Ma
- Computational Systems Biology Laboratory, Department of Biochemistry and Molecular Biology, Institute of Bioinformatics, University of Georgia, Athens, GA 30602, USA
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28
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Parsons JB, Rock CO. Bacterial lipids: metabolism and membrane homeostasis. Prog Lipid Res 2013; 52:249-76. [PMID: 23500459 PMCID: PMC3665635 DOI: 10.1016/j.plipres.2013.02.002] [Citation(s) in RCA: 298] [Impact Index Per Article: 27.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Revised: 02/27/2013] [Accepted: 02/28/2013] [Indexed: 11/29/2022]
Abstract
Membrane lipid homeostasis is a vital facet of bacterial cell physiology. For decades, research in bacterial lipid synthesis was largely confined to the Escherichia coli model system. This basic research provided a blueprint for the biochemistry of lipid metabolism that has largely defined the individual steps in bacterial fatty acid and phospholipids synthesis. The advent of genomic sequencing has revealed a surprising amount of diversity in the genes, enzymes and genetic organization of the components responsible for bacterial lipid synthesis. Although the chemical steps in fatty acid synthesis are largely conserved in bacteria, there are surprising differences in the structure and cofactor requirements for the enzymes that perform these reactions in Gram-positive and Gram-negative bacteria. This review summarizes how the explosion of new information on the diversity of biochemical and genetic regulatory mechanisms has impacted our understanding of bacterial lipid homeostasis. The potential and problems of developing therapeutics that block pathogen phospholipid synthesis are explored and evaluated. The study of bacterial lipid metabolism continues to be a rich source for new biochemistry that underlies the variety and adaptability of bacterial life styles.
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Affiliation(s)
- Joshua B Parsons
- Department of Infectious Diseases, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
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29
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Zarzycki-Siek J, Norris MH, Kang Y, Sun Z, Bluhm AP, McMillan IA, Hoang TT. Elucidating the Pseudomonas aeruginosa fatty acid degradation pathway: identification of additional fatty acyl-CoA synthetase homologues. PLoS One 2013; 8:e64554. [PMID: 23737986 PMCID: PMC3667196 DOI: 10.1371/journal.pone.0064554] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Accepted: 04/16/2013] [Indexed: 01/22/2023] Open
Abstract
The fatty acid (FA) degradation pathway of Pseudomonas aeruginosa, an opportunistic pathogen, was recently shown to be involved in nutrient acquisition during BALB/c mouse lung infection model. The source of FA in the lung is believed to be phosphatidylcholine, the major component of lung surfactant. Previous research indicated that P. aeruginosa has more than two fatty acyl-CoA synthetase genes (fadD; PA3299 and PA3300), which are responsible for activation of FAs using ATP and coenzyme A. Through a bioinformatics approach, 11 candidate genes were identified by their homology to the Escherichia coli FadD in the present study. Four new homologues of fadD (PA1617, PA2893, PA3860, and PA3924) were functionally confirmed by their ability to complement the E. coli fadD mutant on FA-containing media. Growth phenotypes of 17 combinatorial fadD mutants on different FAs, as sole carbon sources, indicated that the four new fadD homologues are involved in FA degradation, bringing the total number of P. aeruginosa fadD genes to six. Of the four new homologues, fadD4 (PA1617) contributed the most to the degradation of different chain length FAs. Growth patterns of various fadD mutants on plant-based perfumery substances, citronellic and geranic acids, as sole carbon and energy sources indicated that fadD4 is also involved in the degradation of these plant-derived compounds. A decrease in fitness of the sextuple fadD mutant, relative to the ΔfadD1D2 mutant, was only observed during BALB/c mouse lung infection at 24 h.
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Affiliation(s)
- Jan Zarzycki-Siek
- Department of Microbiology, University of Hawaii at Manoa, Honolulu, Hawaii, United States of America
| | - Michael H. Norris
- Department of Molecular Bioscience and Bioengineering, University of Hawaii at Manoa, Honolulu, Hawaii, United States of America
| | - Yun Kang
- Department of Microbiology, University of Hawaii at Manoa, Honolulu, Hawaii, United States of America
| | - Zhenxin Sun
- Department of Microbiology, University of Hawaii at Manoa, Honolulu, Hawaii, United States of America
| | - Andrew P. Bluhm
- Department of Microbiology, University of Hawaii at Manoa, Honolulu, Hawaii, United States of America
| | - Ian A. McMillan
- Department of Molecular Bioscience and Bioengineering, University of Hawaii at Manoa, Honolulu, Hawaii, United States of America
| | - Tung T. Hoang
- Department of Microbiology, University of Hawaii at Manoa, Honolulu, Hawaii, United States of America
- Department of Molecular Bioscience and Bioengineering, University of Hawaii at Manoa, Honolulu, Hawaii, United States of America
- * E-mail:
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30
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Cintolesi A, Rodríguez-Moyá M, Gonzalez R. Fatty acid oxidation: systems analysis and applications. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2013; 5:575-85. [DOI: 10.1002/wsbm.1226] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 03/26/2013] [Accepted: 03/29/2013] [Indexed: 12/30/2022]
Affiliation(s)
- Angela Cintolesi
- Department of Chemical and Biomolecular Engineering; Rice University; Houston TX USA
| | - María Rodríguez-Moyá
- Department of Chemical and Biomolecular Engineering; Rice University; Houston TX USA
| | - Ramon Gonzalez
- Department of Chemical and Biomolecular Engineering; Rice University; Houston TX USA
- Department of Bioengineering; Rice University; Houston TX USA
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Rabinovitch-Deere CA, Oliver JWK, Rodriguez GM, Atsumi S. Synthetic biology and metabolic engineering approaches to produce biofuels. Chem Rev 2013; 113:4611-32. [PMID: 23488968 DOI: 10.1021/cr300361t] [Citation(s) in RCA: 134] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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Feng Y, Cronan JE. Crosstalk of Escherichia coli FadR with global regulators in expression of fatty acid transport genes. PLoS One 2012; 7:e46275. [PMID: 23029459 PMCID: PMC3460868 DOI: 10.1371/journal.pone.0046275] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2012] [Accepted: 08/29/2012] [Indexed: 02/03/2023] Open
Abstract
Escherichia coli FadR plays two regulatory roles in fatty acid metabolism. FadR represses the fatty acid degradation (fad) system and activates the unsaturated fatty acid synthetic pathway. Cross-talk between E. coli FadR and the ArcA-ArcB oxygen-responsive two-component system was observed that resulted in diverse regulation of certain fad regulon β-oxidation genes. We have extended such analyses to the fadL and fadD genes, the protein products of which are required for long chain fatty acid transport and have also studied the role of a third global regulator, the CRP-cAMP complex. The promoters of both the fadL and fadD genes contain two experimentally validated FadR-binding sites plus binding sites for ArcA and CRP-cAMP. Despite the presence of dual binding sites FadR only modestly regulates expression of these genes, indicating that the number of binding sites does not determine regulatory strength. We report complementary in vitro and in vivo studies indicating that the CRP-cAMP complex directly activates expression of fadL and fadD as well as the β-oxidation gene, fadH. The physiological relevance of the fadL and fadD transcription data was validated by direct assays of long chain fatty acid transport.
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Affiliation(s)
- Youjun Feng
- Department of Microbiology, University of Illinois, Urbana, Illinois, United States of America
| | - John E. Cronan
- Department of Microbiology, University of Illinois, Urbana, Illinois, United States of America
- Department of Biochemistry, University of Illinois, Urbana, Illinois, United States of America
- * E-mail:
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Abstract
Regulatory networks inferred from microarray data sets provide an estimated blueprint of the functional interactions taking place under the assayed experimental conditions. In each of these experiments, the gene expression pathway exerts a finely tuned control simultaneously over all genes relevant to the cellular state. This renders most pairs of those genes significantly correlated, and therefore, the challenge faced by every method that aims at inferring a molecular regulatory network from microarray data, lies in distinguishing direct from indirect interactions. A straightforward solution to this problem would be to move directly from bivariate to multivariate statistical approaches. However, the daunting dimension of typical microarray data sets, with a number of genes p several orders of magnitude larger than the number of samples n, precludes the application of standard multivariate techniques and confronts the biologist with sophisticated procedures that address this situation. We have introduced a new way to approach this problem in an intuitive manner, based on limited-order partial correlations, and in this chapter we illustrate this method through the R package qpgraph, which forms part of the Bioconductor project and is available at its Web site.
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Babujee L, Apodaca J, Balakrishnan V, Liss P, Kiley PJ, Charkowski AO, Glasner JD, Perna NT. Evolution of the metabolic and regulatory networks associated with oxygen availability in two phytopathogenic enterobacteria. BMC Genomics 2012; 13:110. [PMID: 22439737 PMCID: PMC3349551 DOI: 10.1186/1471-2164-13-110] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Accepted: 03/22/2012] [Indexed: 01/31/2023] Open
Abstract
Background Dickeya dadantii and Pectobacterium atrosepticum are phytopathogenic enterobacteria capable of facultative anaerobic growth in a wide range of O2 concentrations found in plant and natural environments. The transcriptional response to O2 remains under-explored for these and other phytopathogenic enterobacteria although it has been well characterized for animal-associated genera including Escherichia coli and Salmonella enterica. Knowledge of the extent of conservation of the transcriptional response across orthologous genes in more distantly related species is useful to identify rates and patterns of regulon evolution. Evolutionary events such as loss and acquisition of genes by lateral transfer events along each evolutionary branch results in lineage-specific genes, some of which may have been subsequently incorporated into the O2-responsive stimulon. Here we present a comparison of transcriptional profiles measured using densely tiled oligonucleotide arrays for two phytopathogens, Dickeya dadantii 3937 and Pectobacterium atrosepticum SCRI1043, grown to mid-log phase in MOPS minimal medium (0.1% glucose) with and without O2. Results More than 7% of the genes of each phytopathogen are differentially expressed with greater than 3-fold changes under anaerobic conditions. In addition to anaerobic metabolism genes, the O2 responsive stimulon includes a variety of virulence and pathogenicity-genes. Few of these genes overlap with orthologous genes in the anaerobic stimulon of E. coli. We define these as the conserved core, in which the transcriptional pattern as well as genetic architecture are well preserved. This conserved core includes previously described anaerobic metabolic pathways such as fermentation. Other components of the anaerobic stimulon show variation in genetic content, genome architecture and regulation. Notably formate metabolism, nitrate/nitrite metabolism, and fermentative butanediol production, differ between E. coli and the phytopathogens. Surprisingly, the overlap of the anaerobic stimulon between the phytopathogens is also relatively small considering that they are closely related, occupy similar niches and employ similar strategies to cause disease. There are cases of interesting divergences in the pattern of transcription of genes between Dickeya and Pectobacterium for virulence-associated subsystems including the type VI secretion system (T6SS), suggesting that fine-tuning of the stimulon impacts interaction with plants or competing microbes. Conclusions The small number of genes (an even smaller number if we consider operons) comprising the conserved core transcriptional response to O2 limitation demonstrates the extent of regulatory divergence prevalent in the Enterobacteriaceae. Our orthology-driven comparative transcriptomics approach indicates that the adaptive response in the eneterobacteria is a result of interaction of core (regulators) and lineage-specific (structural and regulatory) genes. Our subsystems based approach reveals that similar phenotypic outcomes are sometimes achieved by each organism using different genes and regulatory strategies.
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Affiliation(s)
- Lavanya Babujee
- Biotechnology Center, University of Wisconsin-Madison, WI, USA
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Engineered reversal of the β-oxidation cycle for the synthesis of fuels and chemicals. Nature 2011; 476:355-9. [PMID: 21832992 DOI: 10.1038/nature10333] [Citation(s) in RCA: 405] [Impact Index Per Article: 31.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Accepted: 06/23/2011] [Indexed: 01/19/2023]
Abstract
Advanced (long-chain) fuels and chemicals are generated from short-chain metabolic intermediates through pathways that require carbon-chain elongation. The condensation reactions mediating this carbon-carbon bond formation can be catalysed by enzymes from the thiolase superfamily, including β-ketoacyl-acyl-carrier protein (ACP) synthases, polyketide synthases, 3-hydroxy-3-methylglutaryl-CoA synthases, and biosynthetic thiolases. Pathways involving these enzymes have been exploited for fuel and chemical production, with fatty-acid biosynthesis (β-ketoacyl-ACP synthases) attracting the most attention in recent years. Degradative thiolases, which are part of the thiolase superfamily and naturally function in the β-oxidation of fatty acids, can also operate in the synthetic direction and thus enable carbon-chain elongation. Here we demonstrate that a functional reversal of the β-oxidation cycle can be used as a metabolic platform for the synthesis of alcohols and carboxylic acids with various chain lengths and functionalities. This pathway operates with coenzyme A (CoA) thioester intermediates and directly uses acetyl-CoA for acyl-chain elongation (rather than first requiring ATP-dependent activation to malonyl-CoA), characteristics that enable product synthesis at maximum carbon and energy efficiency. The reversal of the β-oxidation cycle was engineered in Escherichia coli and used in combination with endogenous dehydrogenases and thioesterases to synthesize n-alcohols, fatty acids and 3-hydroxy-, 3-keto- and trans-Δ(2)-carboxylic acids. The superior nature of the engineered pathway was demonstrated by producing higher-chain linear n-alcohols (C ≥ 4) and extracellular long-chain fatty acids (C > 10) at higher efficiency than previously reported. The ubiquitous nature of β-oxidation, aldehyde/alcohol dehydrogenase and thioesterase enzymes has the potential to enable the efficient synthesis of these products in other industrial organisms.
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Evans MR, Fink RC, Vazquez-Torres A, Porwollik S, Jones-Carson J, McClelland M, Hassan HM. Analysis of the ArcA regulon in anaerobically grown Salmonella enterica sv. Typhimurium. BMC Microbiol 2011; 11:58. [PMID: 21418628 PMCID: PMC3075218 DOI: 10.1186/1471-2180-11-58] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2010] [Accepted: 03/21/2011] [Indexed: 12/18/2022] Open
Abstract
Background Salmonella enterica serovar Typhimurium (S. Typhimurium) is a Gram-negative pathogen that must successfully adapt to the broad fluctuations in the concentration of dissolved dioxygen encountered in the host. In Escherichia coli, ArcA (Aerobic Respiratory Control) helps the cells to sense and respond to the presence of dioxygen. The global role of ArcA in E. coli is well characterized; however, little is known about its role in anaerobically grown S. Typhimurium. Results We compared the transcriptional profiles of the virulent wild-type (WT) strain (ATCC 14028s) and its isogenic arcA mutant grown under anaerobic conditions. We found that ArcA directly or indirectly regulates 392 genes (8.5% of the genome); of these, 138 genes are poorly characterized. Regulation by ArcA in S. Typhimurium is similar, but distinct from that in E. coli. Thus, genes/operons involved in core metabolic pathways (e.g., succinyl-CoA, fatty acid degradation, cytochrome oxidase complexes, flagellar biosynthesis, motility, and chemotaxis) were regulated similarly in the two organisms. However, genes/operons present in both organisms, but regulated differently by ArcA in S. Typhimurium included those coding for ethanolamine utilization, lactate transport and metabolism, and succinate dehydrogenases. Salmonella-specific genes/operons regulated by ArcA included those required for propanediol utilization, flagellar genes (mcpAC, cheV), Gifsy-1 prophage genes, and three SPI-3 genes (mgtBC, slsA, STM3784). In agreement with our microarray data, the arcA mutant was non-motile, lacked flagella, and was as virulent in mice as the WT. Additionally, we identified a set of 120 genes whose regulation was shared with the anaerobic redox regulator, Fnr. Conclusion(s) We have identified the ArcA regulon in anaerobically grown S. Typhimurium. Our results demonstrated that in S. Typhimurium, ArcA serves as a transcriptional regulator coordinating cellular metabolism, flagella biosynthesis, and motility. Furthermore, ArcA and Fnr share in the regulation of 120 S. Typhimurium genes.
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Affiliation(s)
- Matthew R Evans
- Department of Microbiology, North Carolina State University, Raleigh, North Carolina 27695-7615, USA
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Agari Y, Agari K, Sakamoto K, Kuramitsu S, Shinkai A. TetR-family transcriptional repressor Thermus thermophilus FadR controls fatty acid degradation. MICROBIOLOGY-SGM 2011; 157:1589-1601. [PMID: 21349973 DOI: 10.1099/mic.0.048017-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In the extremely thermophilic bacterium Thermus thermophilus HB8, one of the four TetR-family transcriptional regulators, which we named T. thermophilus FadR, negatively regulated the expression of several genes, including those involved in fatty acid degradation, both in vivo and in vitro. T. thermophilus FadR repressed the expression of the target genes by binding pseudopalindromic sequences covering the predicted -10 hexamers of their promoters, and medium-to-long straight-chain (C10-18) fatty acyl-CoA molecules were effective for transcriptional derepression. An X-ray crystal structure analysis revealed that T. thermophilus FadR bound one lauroyl (C12)-CoA molecule per FadR monomer, with its acyl chain moiety in the centre of the FadR molecule, enclosed within a tunnel-like substrate-binding pocket surrounded by hydrophobic residues, and the CoA moiety interacting with basic residues on the protein surface. The growth of T. thermophilus HB8, with palmitic acid as the sole carbon source, increased the expression of FadR-regulated genes. These results indicate that in T. thermophilus HB8, medium-to-long straight-chain fatty acids can be used for metabolic energy under the control of FadR, although the major fatty acids found in this strain are iso- and anteiso-branched-chain (C15 and 17) fatty acids.
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Affiliation(s)
- Yoshihiro Agari
- RIKEN SPring-8 Center, Harima Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
| | - Kazuko Agari
- RIKEN SPring-8 Center, Harima Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
| | - Keiko Sakamoto
- RIKEN SPring-8 Center, Harima Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
| | - Seiki Kuramitsu
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan.,RIKEN SPring-8 Center, Harima Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
| | - Akeo Shinkai
- RIKEN SPring-8 Center, Harima Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
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Overlapping repressor binding sites result in additive regulation of Escherichia coli FadH by FadR and ArcA. J Bacteriol 2010; 192:4289-99. [PMID: 20622065 DOI: 10.1128/jb.00516-10] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Escherichia coli fadH encodes a 2,4-dienoyl reductase that plays an auxiliary role in beta-oxidation of certain unsaturated fatty acids. In the 2 decades since its discovery, FadH biochemistry has been studied extensively. However, the genetic regulation of FadH has been explored only partially. Here we report mapping of the fadH promoter and document its complex regulation by three independent regulators, the fatty acid degradation FadR repressor, the oxygen-responsive ArcA-ArcB two-component system, and the cyclic AMP receptor protein-cyclic AMP (CRP-cAMP) complex. Electrophoretic mobility shift assays demonstrated that FadR binds to the fadH promoter region and that this binding can be specifically reversed by long-chain acyl-coenzyme A (CoA) thioesters. In vivo data combining transcriptional lacZ fusion and real-time quantitative PCR (qPCR) analyses indicated that fadH is strongly repressed by FadR, in agreement with induction of fadH by long-chain fatty acids. Inactivation of arcA increased fadH transcription by >3-fold under anaerobic conditions. Moreover, fadH expression was increased 8- to 10-fold under anaerobic conditions upon deletion of both the fadR and the arcA gene, indicating that anaerobic expression is additively repressed by FadR and ArcA-ArcB. Unlike fadM, a newly reported member of the E. coli fad regulon that encodes another auxiliary beta-oxidation enzyme, fadH was activated by the CRP-cAMP complex in a manner similar to those of the prototypical fad genes. In the absence of the CRP-cAMP complex, repression of fadH expression by both FadR and ArcA-ArcB was very weak, suggesting a possible interplay with other DNA binding proteins.
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Genome analysis of Moraxella catarrhalis strain BBH18, [corrected] a human respiratory tract pathogen. J Bacteriol 2010; 192:3574-83. [PMID: 20453089 DOI: 10.1128/jb.00121-10] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Moraxella catarrhalis is an emerging human-restricted respiratory tract pathogen that is a common cause of childhood otitis media and exacerbations of chronic obstructive pulmonary disease in adults. Here, we report the first completely assembled and annotated genome sequence of an isolate of M. catarrhalis, strain RH4, which originally was isolated from blood of an infected patient. The RH4 genome consists of 1,863,286 nucleotides that form 1,886 protein-encoding genes. Comparison of the RH4 genome to the ATCC 43617 contigs demonstrated that the gene content of both strains is highly conserved. In silico phylogenetic analyses based on both 16S rRNA and multilocus sequence typing revealed that RH4 belongs to the seroresistant lineage. We were able to identify almost the entire repertoire of known M. catarrhalis virulence factors and mapped the members of the biosynthetic pathways for lipooligosaccharide, peptidoglycan, and type IV pili. Reconstruction of the central metabolic pathways suggested that RH4 relies on fatty acid and acetate metabolism, as the genes encoding the enzymes required for the glyoxylate pathway, the tricarboxylic acid cycle, the gluconeogenic pathway, the nonoxidative branch of the pentose phosphate pathway, the beta-oxidation pathway of fatty acids, and acetate metabolism were present. Moreover, pathways important for survival under challenging in vivo conditions, such as the iron-acquisition pathways, nitrogen metabolism, and oxidative stress responses, were identified. Finally, we showed by microarray expression profiling that approximately 88% of the predicted coding sequences are transcribed under in vitro conditions. Overall, these results provide a foundation for future research into the mechanisms of M. catarrhalis pathogenesis and vaccine development.
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Tiwari N, Woods L, Haley R, Kight A, Goforth R, Clark K, Ataai M, Henry R, Beitle R. Identification and characterization of native proteins of Escherichia coli BL-21 that display affinity towards Immobilized Metal Affinity Chromatography and Hydrophobic Interaction Chromatography Matrices. Protein Expr Purif 2010; 70:191-5. [DOI: 10.1016/j.pep.2009.10.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2009] [Revised: 10/28/2009] [Accepted: 10/29/2009] [Indexed: 10/20/2022]
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Su LK, Lu CP, Wang Y, Cao DM, Sun JH, Yan YX. Lysogenic infection of a Shiga toxin 2-converting bacteriophage changes host gene expression, enhances host acid resistance and motility. Mol Biol 2010. [DOI: 10.1134/s0026893310010085] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Feng Y, Cronan JE. Escherichia coli unsaturated fatty acid synthesis: complex transcription of the fabA gene and in vivo identification of the essential reaction catalyzed by FabB. J Biol Chem 2009; 284:29526-35. [PMID: 19679654 PMCID: PMC2785586 DOI: 10.1074/jbc.m109.023440] [Citation(s) in RCA: 141] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2009] [Revised: 07/06/2009] [Indexed: 11/06/2022] Open
Abstract
Although the unsaturated fatty acid (UFA) synthetic pathway of Escherichia coli is the prototype of such pathways, several unresolved issues have accumulated over the years. The key players are the fabA and fabB genes. Earlier studies of fabA transcription showed that the gene was transcribed from two promoters, with one being positively regulated by the FadR protein. The other weaker promoter (which could not be mapped with the technology then available) was considered constitutive because its function was independent of FadR. However, the FabR negative regulator was recently shown to represses fabA transcription. We report that the weak promoter overlaps the FadR-dependent promoter and is regulated by FabR. This promoter is strictly conserved in all E. coli and Salmonella enterica genomes sequenced to date and is thought to provide insurance against inappropriate regulation of fabA transcription by exogenous saturated fatty acids. Also, the fabAup promoter, a mutant promoter previously isolated by selection for increased FabA activity, was shown to be a promoter created de novo by a four-base deletion within the gene located immediately upstream of fabA. Demonstration of the key UFA synthetic reaction catalyzed by FabB has been elusive, although it was known to catalyze an elongation reaction. Strains lacking FabB are UFA auxotrophs indicating that the enzyme catalyzes an essential step in UFA synthesis. Using thioesterases specific for hydrolysis of short chain acyl-ACPs, the intermediates of the UFA synthetic pathway have been followed in vivo for the first time. These experiments showed that a fabB mutant strain accumulated less cis-5-dodecenoic acid than the parental wild-type strain. These data indicate that the key reaction in UFA synthesis catalyzed by FabB is elongation of the cis-3-decenoyl-ACP produced by FabA.
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Affiliation(s)
| | - John E. Cronan
- From the Departments of Microbiology and
- Biochemistry, University of Illinois, Urbana, Illinois 61801
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43
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Plakunov VK, Shelemekh OV. Mechanisms of oxygen regulation in microorganisms. Microbiology (Reading) 2009. [DOI: 10.1134/s0026261709050026] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Feng Y, Cronan JE. A new member of the Escherichia coli fad regulon: transcriptional regulation of fadM (ybaW). J Bacteriol 2009; 191:6320-8. [PMID: 19684132 PMCID: PMC2753046 DOI: 10.1128/jb.00835-09] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2009] [Accepted: 08/09/2009] [Indexed: 11/20/2022] Open
Abstract
Recently, Nie and coworkers (L. Nie, Y. Ren, A. Janakiraman, S. Smith, and H. Schulz, Biochemistry 47:9618-9626, 2008) reported a new Escherichia coli thioesterase encoded by the ybaW gene that cleaves the thioester bonds of inhibitory acyl-coenzyme A (CoA) by-products generated during beta-oxidation of certain unsaturated fatty acids. These authors suggested that ybaW expression might be regulated by FadR, the repressor of the fad (fatty acid degradation) regulon. We report mapping of the ybaW promoter and show that ybaW transcription responded to FadR in vivo. Moreover, purified FadR bound to a DNA sequence similar to the canonical FadR binding site located upstream of the ybaW coding sequence and was released from the promoter upon the addition of long-chain acyl-CoA thioesters. We therefore propose the designation fadM in place of ybaW. Although FadR regulation of fadM expression had the pattern typical of fad regulon genes, its modulation by the cyclic AMP (cAMP) receptor protein-cAMP complex (CRP-cAMP) global regulator was the opposite of that normally observed. CRP-cAMP generally acts as an activator of fad gene expression, consistent with the low status of fatty acids as carbon sources. However, glucose growth stimulated fadM expression relative to acetate growth, as did inactivation of CRP-cAMP, indicating that the complex acts as a negative regulator of this gene. The stimulation of fadM expression seen upon deletion of the gene encoding adenylate cyclase (Deltacya) was reversed by supplementation of the growth medium with cAMP. Nie and coworkers also reported that growth on a conjugated linoleic acid isomer yields much higher levels of FadM thioesterase activity than does growth on oleic acid. In contrast, we found that the conjugated linoleic acid isomer was only a weak inducer of fadM expression. Although the gene is not essential for growth, the high basal level of fadM expression under diverse growth conditions suggests that the encoded thioesterase has functions in addition to beta-oxidation.
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Affiliation(s)
- Youjun Feng
- Department of Microbiology, University of Illinois, B103 Chemical and Life Sciences Laboratory, 601 S. Goodwin Ave., Urbana, IL 61801, USA
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Grainger DC, Lee DJ, Busby SJW. Direct methods for studying transcription regulatory proteins and RNA polymerase in bacteria. Curr Opin Microbiol 2009; 12:531-5. [PMID: 19762273 DOI: 10.1016/j.mib.2009.08.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2009] [Revised: 07/22/2009] [Accepted: 08/14/2009] [Indexed: 10/20/2022]
Abstract
Transcription factors and sigma factors play a major role in bacterial gene regulation by guiding the distribution of RNA polymerase between the promoters of different transcription units in response to changes in the environment. For 40 years Escherichia coli K-12 has been the paradigm for investigating this regulation and most studies have focused on small numbers of promoters studied by a combination of genetics and biochemistry. Since the first complete sequence for a bacterial genome was reported, the emphasis has switched to studying transcription on a global scale, with transcriptomics and bioinformatics becoming the methods of choice. Here we discuss two complementary direct experimental methods for studying transcription factors and sigma factors and we outline their potential use in rapidly establishing the regulatory networks in newly sequenced bacteria.
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Affiliation(s)
- David C Grainger
- Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, UK
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Yanover C, Singh M, Zaslavsky E. M are better than one: an ensemble-based motif finder and its application to regulatory element prediction. ACTA ACUST UNITED AC 2009; 25:868-74. [PMID: 19223448 DOI: 10.1093/bioinformatics/btp090] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
MOTIVATION Identifying regulatory elements in genomic sequences is a key component in understanding the control of gene expression. Computationally, this problem is often addressed by motif discovery, where the goal is to find a set of mutually similar subsequences within a collection of input sequences. Though motif discovery is widely studied and many approaches to it have been suggested, it remains a challenging and as yet unresolved problem. RESULTS We introduce SAMF (Solution-Aggregating Motif Finder), a novel approach for motif discovery. SAMF is based on a Markov Random Field formulation, and its key idea is to uncover and aggregate multiple statistically significant solutions to the given motif finding problem. In contrast to many earlier methods, SAMF does not require prior estimates on the number of motif instances present in the data, is not limited by motif length, and allows motifs to overlap. Though SAMF is broadly applicable, these features make it particularly well suited for addressing the challenges of prokaryotic regulatory element detection. We test SAMF's ability to find transcription factor binding sites in an Escherichia coli dataset and show that it outperforms previous methods. Additionally, we uncover a number of previously unidentified binding sites in this data, and provide evidence that they correspond to actual regulatory elements. SUPPLEMENTARY INFORMATION Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Chen Yanover
- Fred Hutchinson Cancer Research Center, Seattle, WA, USA.
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Castelo R, Roverato A. Reverse Engineering Molecular Regulatory Networks from Microarray Data with qp-Graphs. J Comput Biol 2009; 16:213-27. [DOI: 10.1089/cmb.2008.08tt] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Robert Castelo
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona, Spain
- Research Program on Biomedical Informatics, Institut Municipal d'Investigació Mèdica, Barcelona, Spain
| | - Alberto Roverato
- Department of Statistical Science, Università di Bologna, Bologna, Italy
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Abstract
While hundreds of microbial genomes are sequenced, the challenge remains to define their cis-regulatory maps. Here, we present a comparative genomic analysis of the cis-regulatory map of Shewanella oneidensis, an important model organism for bioremediation because of its extraordinary abilities to use a wide variety of metals and organic molecules as electron acceptors in respiration. First, from the experimentally verified transcriptional regulatory networks of Escherichia coli, we inferred 24 DNA motifs that are conserved in S. oneidensis. We then applied a new comparative approach on five Shewanella genomes that allowed us to systematically identify 194 nonredundant palindromic DNA motifs and corresponding regulons in S. oneidensis. Sixty-four percent of the predicted motifs are conserved in at least three of the seven newly sequenced and distantly related Shewanella genomes. In total, we obtained 209 unique DNA motifs in S. oneidensis that cover 849 unique transcription units. Besides conservation in other genomes, 77 of these motifs are supported by at least one additional type of evidence, including matching to known transcription factor binding motifs and significant functional enrichment or expression coherence of the corresponding target genes. Using the same approach on a more focused gene set, 990 differentially expressed genes derived from published microarray data of S. oneidensis during exposure to metal ions, we identified 31 putative cis-regulatory motifs (16 with at least one type of additional supporting evidence) that are potentially involved in the process of metal reduction. The majority (18/31) of those motifs had been found in our whole-genome comparative approach, further demonstrating that such an approach is capable of uncovering a large fraction of the regulatory map of a genome even in the absence of experimental data. The integrated computational approach developed in this study provides a useful strategy to identify genome-wide cis-regulatory maps and a novel avenue to explore the regulatory pathways for particular biological processes in bacterial systems.
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Affiliation(s)
- Jiajian Liu
- Department of Genetics, Washington University School of Medicine, 660 S Euclid, Box 8232, St Louis, MO 63110, USA
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Pettinari MJ, Nikel PI, Ruiz JA, Méndez BS. ArcA redox mutants as a source of reduced bioproducts. J Mol Microbiol Biotechnol 2008; 15:41-7. [PMID: 18349549 DOI: 10.1159/000111991] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Escherichia coli and other facultative anaerobes can adapt their metabolism according to oxygen availability by means of aerobic and anaerobic respiration and fermentation. ArcAB is a two-component signal transduction system that controls, at the transcriptional level, the choice of energy generation pathway according to the intracellular redox state. High throughput studies on different redox regulator mutants, involving transcriptome analysis, RT-PCR and phenotypic arrays enabled the elucidation of a repertoire of operons coordinated by ArcA which extended beyond respiration control including, among others, those which code for survival, chromosome replication and degradation of fatty acids. Flux analysis by (13)C labeling provided new clues to the understanding of the distribution of metabolites mediated by ArcAB. The genetic manipulation of this regulator proved to be useful for the generation of reduced products of commercial value.
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Affiliation(s)
- M Julia Pettinari
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
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Cho BK, Knight EM, Barrett CL, Palsson BØ. Genome-wide analysis of Fis binding in Escherichia coli indicates a causative role for A-/AT-tracts. Genome Res 2008; 18:900-10. [PMID: 18340041 DOI: 10.1101/gr.070276.107] [Citation(s) in RCA: 139] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
We determined the genome-wide distribution of the nucleoid-associated protein Fis in Escherichia coli using chromatin immunoprecipitation coupled with high-resolution whole genome-tiling microarrays. We identified 894 Fis-associated regions across the E. coli genome. A significant number of these binding sites were found within open reading frames (33%) and between divergently transcribed transcripts (5%). Analysis indicates that A-tracts and AT-tracts are an important signal for preferred Fis-binding sites, and that A(6)-tracts in particular constitute a high-affinity signal that dictates Fis phasing in stretches of DNA containing multiple and variably spaced A-tracts and AT-tracts. Furthermore, we find evidence for an average of two Fis-binding regions per supercoiling domain in the chromosome of exponentially growing cells. Transcriptome analysis shows that approximately 21% of genes are affected by the deletion of fis; however, the changes in magnitude are small. To address the differential Fis bindings under growth environment perturbation, ChIP-chip analysis was performed using cells grown under aerobic and anaerobic growth conditions. Interestingly, the Fis-binding regions are almost identical in aerobic and anaerobic growth conditions-indicating that the E. coli genome topology mediated by Fis is superficially identical in the two conditions. These novel results provide new insight into how Fis modulates DNA topology at a genome scale and thus advance our understanding of the architectural bases of the E. coli nucleoid.
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Affiliation(s)
- Byung-Kwan Cho
- Department of Bioengineering, University of California-San Diego, La Jolla, California 92093-0412, USA
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