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Kim GY, Yang J, Han YH, Seo SW. Synthetic redesign of Escherichia coli W for faster metabolism of sugarcane molasses. Microb Cell Fact 2024; 23:242. [PMID: 39252026 PMCID: PMC11382391 DOI: 10.1186/s12934-024-02520-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2024] [Accepted: 09/02/2024] [Indexed: 09/11/2024] Open
Abstract
BACKGROUND Sugarcane molasses, rich in sucrose, glucose, and fructose, offers a promising carbon source for industrial fermentation due to its abundance and low cost. However, challenges arise from the simultaneous utilization of multiple sugars and carbon catabolite repression (CCR). Despite its nutritional content, sucrose metabolism in Escherichia coli, except for W strain, remains poorly understood, hindering its use in microbial fermentation. In this study, E. coli W was engineered to enhance sugar consumption rates and overcome CCR. This was achieved through the integration of a synthetically designed csc operon and the optimization of glucose and fructose co-utilization pathways. These advancements facilitate efficient utilization of sugarcane molasses for the production of 3-hydroxypropionic acid (3-HP), contributing to sustainable biochemical production processes. RESULTS In this study, we addressed challenges associated with sugar metabolism in E. coli W, focusing on enhancing sucrose consumption and improving glucose-fructose co-utilization. Through targeted engineering of the sucrose utilization system, we achieved accelerated sucrose consumption rates by modulating the expression of the csc operon components, cscB, cscK, cscA, and cscR. Our findings revealed that monocistronic expression of the csc genes with the deletion of cscR, led to optimal sucrose utilization without significant growth burden. Furthermore, we successfully alleviated fructose catabolite repression by modulating the binding dynamics of FruR with the fructose PTS regulon, enabling near-equivalent co-utilization of glucose and fructose. To validate the industrial applicability of our engineered strain, we pursued 3-HP production from sugarcane molasses. By integrating heterologous genes and optimizing metabolic pathways, we achieved improvements in 3-HP titers compared to previous studies. Additionally, glyceraldehyde-3-phosphate dehydrogenase (gapA) repression aids in carbon flux redistribution, enhancing molasses conversion to 3-HP. CONCLUSIONS Despite limitations in sucrose metabolism, the redesigned E. coli W strain, adept at utilizing sugarcane molasses, is a valuable asset for industrial fermentation. Its synthetic csc operon enhances sucrose consumption, while mitigating CCR improves glucose-fructose co-utilization. These enhancements, coupled with repression of gapA, aim to efficiently convert sugarcane molasses into 3-HP, addressing limitations in sucrose and fructose metabolism for industrial applications.
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Affiliation(s)
- Gi Yeon Kim
- Interdisciplinary Program in Bioengineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, South Korea
| | - Jina Yang
- Department of Chemical Engineering, Jeju National University, 102, Jejudaehak-ro, Jeju-si, Jeju-do, 63243, Korea
| | - Yong Hee Han
- Interdisciplinary Program in Bioengineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, South Korea
- School of Biological Sciences and Biotechnology, Graduate School, and School of Biological Sciences and Technology, Chonnam National University, Yongbong-ro 77, Gwangju, 61186, South Korea
| | - Sang Woo Seo
- Interdisciplinary Program in Bioengineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, South Korea.
- School of Chemical and Biological Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, South Korea.
- Institute of Chemical Processes, and Bio-MAX Institute, and Institute of Bio Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, South Korea.
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Fordjour E, Liu CL, Hao Y, Sackey I, Yang Y, Liu X, Li Y, Tan T, Bai Z. Engineering Escherichia coli BL21 (DE3) for high-yield production of germacrene A, a precursor of β-elemene via combinatorial metabolic engineering strategies. Biotechnol Bioeng 2023; 120:3039-3056. [PMID: 37309999 DOI: 10.1002/bit.28467] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Revised: 05/31/2023] [Accepted: 06/03/2023] [Indexed: 06/14/2023]
Abstract
β-elemene is one of the most commonly used antineoplastic drugs in cancer treatment. As a plant-derived natural chemical, biologically engineering microorganisms to produce germacrene A to be converted to β-elemene harbors great expectations since chemical synthesis and plant isolation methods come with their production deficiencies. In this study, we report the design of an Escherichia coli cell factory for the de novo production of germacrene A to be converted to β-elemene from a simple carbon source. A series of systematic approaches of engineering the isoprenoid and central carbon pathways, translational and protein engineering of the sesquiterpene synthase, and exporter engineering yielded high-efficient β-elemene production. Specifically, deleting competing pathways in the central carbon pathway ensured the availability of acetyl-coA, pyruvate, and glyceraldehyde-3-phosphate for the isoprenoid pathways. Adopting lycopene color as a high throughput screening method, an optimized NSY305N was obtained via error-prone polymerase chain reaction mutagenesis. Further overexpression of key pathway enzymes, exporter genes, and translational engineering produced 1161.09 mg/L of β-elemene in a shake flask. Finally, we detected the highest reported titer of 3.52 g/L of β-elemene and 2.13 g/L germacrene A produced by an E. coli cell factory in a 4-L fed-batch fermentation. The systematic engineering reported here generally applies to microbial production of a broader range of chemicals. This illustrates that rewiring E. coli central metabolism is viable for producing acetyl-coA-derived and pyruvate-derived molecules cost-effectively.
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Affiliation(s)
- Eric Fordjour
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, China
- National Engineering Research Center of Cereal Fermentation, and Food Biomanufacturing, Jiangnan University, Wuxi, China
- Jiangsu Provincial Research Centre for Bioactive Product Processing Technology, Jiangnan University, Wuxi, China
| | - Chun-Li Liu
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, China
- National Engineering Research Center of Cereal Fermentation, and Food Biomanufacturing, Jiangnan University, Wuxi, China
- Jiangsu Provincial Research Centre for Bioactive Product Processing Technology, Jiangnan University, Wuxi, China
| | - Yunpeng Hao
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, China
- National Engineering Research Center of Cereal Fermentation, and Food Biomanufacturing, Jiangnan University, Wuxi, China
- Jiangsu Provincial Research Centre for Bioactive Product Processing Technology, Jiangnan University, Wuxi, China
| | - Isaac Sackey
- Department of Biological Sciences, Faculty of Biosciences, University for Development Studies, Tamale, Ghana
| | - Yankun Yang
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, China
- National Engineering Research Center of Cereal Fermentation, and Food Biomanufacturing, Jiangnan University, Wuxi, China
- Jiangsu Provincial Research Centre for Bioactive Product Processing Technology, Jiangnan University, Wuxi, China
| | - Xiuxia Liu
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, China
- National Engineering Research Center of Cereal Fermentation, and Food Biomanufacturing, Jiangnan University, Wuxi, China
- Jiangsu Provincial Research Centre for Bioactive Product Processing Technology, Jiangnan University, Wuxi, China
| | - Ye Li
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, China
- National Engineering Research Center of Cereal Fermentation, and Food Biomanufacturing, Jiangnan University, Wuxi, China
- Jiangsu Provincial Research Centre for Bioactive Product Processing Technology, Jiangnan University, Wuxi, China
| | - Tianwei Tan
- College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, China
| | - Zhonghu Bai
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, China
- National Engineering Research Center of Cereal Fermentation, and Food Biomanufacturing, Jiangnan University, Wuxi, China
- Jiangsu Provincial Research Centre for Bioactive Product Processing Technology, Jiangnan University, Wuxi, China
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3
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Zhu Y, Gao H, Zhang J, Zhao J, Qi Q, Wang Q. De novo design of the global transcriptional factor Cra-regulated promoters enables highly sensitive glycolysis flux biosensor for dynamic metabolic control. Microb Biotechnol 2023; 16:605-617. [PMID: 36541030 PMCID: PMC9948231 DOI: 10.1111/1751-7915.14166] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2022] [Revised: 10/09/2022] [Accepted: 10/19/2022] [Indexed: 12/24/2022] Open
Abstract
Glycolytic flux is a fundamental index in microbial cell factories. A glycolytic flux biosensor that can monitor glucose metabolism efficiency is a promising strategy in rewiring metabolic flux to balance growth and biosynthesis. A key design feature of the glycolytic flux biosensors is the interaction between the global transcriptional factor Cra and its regulated promoters. However, overexpression and mutation of Cra has unpredictable effects on global metabolism in Escherichia coli. Therefore, new orthogonal biosensor design strategies should be developed to circumvent metabolic issues. In this report, the promoters in glycolytic flux biosensor were replaced with synthetic promoters of varying strengths or phage-derived promoters, and the Cra DNA-binding sites were deployed into promoters at different positions and distances to yield biosensors. The de nova biosensors that depended on Cra could sense Fructose-1,6-diphosphate (FBP) with broad dynamic ranges and low basal leakage. Then the negative-response biosensors were applied to fine-tune the target ATP synthesis gene, leading to the desired increase in pyruvate production (the highest 9.66 g/L) and cell growth. Moreover, the membrane synthesis gene plsC was also dynamically activated by the positive-response biosensor, leading to effective accumulation of lycopene in the cell membrane and a 50-fold increase in lycopene titre (100.3 mg/L) when compared with the control strain, demonstrating the effective and broader usages of our biosensors.
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Affiliation(s)
- Yuan Zhu
- National Glycoengineering Research Center, State Key Laboratory of Microbial Technology, Shandong University, Qingdao, China
| | - Huaxiao Gao
- National Glycoengineering Research Center, State Key Laboratory of Microbial Technology, Shandong University, Qingdao, China
| | - Jian Zhang
- National Glycoengineering Research Center, State Key Laboratory of Microbial Technology, Shandong University, Qingdao, China
| | - Jingyu Zhao
- National Glycoengineering Research Center, State Key Laboratory of Microbial Technology, Shandong University, Qingdao, China
| | - Qingsheng Qi
- National Glycoengineering Research Center, State Key Laboratory of Microbial Technology, Shandong University, Qingdao, China
| | - Qian Wang
- National Glycoengineering Research Center, State Key Laboratory of Microbial Technology, Shandong University, Qingdao, China
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Baek J, Yoon H. Cyclic di-GMP Modulates a Metabolic Flux for Carbon Utilization in Salmonella enterica Serovar Typhimurium. Microbiol Spectr 2023; 11:e0368522. [PMID: 36744926 PMCID: PMC10100716 DOI: 10.1128/spectrum.03685-22] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Accepted: 01/16/2023] [Indexed: 02/07/2023] Open
Abstract
Salmonella enterica serovar Typhimurium is an enteric pathogen spreading via the fecal-oral route. Transmission across humans, animals, and environmental reservoirs has forced this pathogen to rapidly respond to changing environments and adapt to new environmental conditions. Cyclic di-GMP (c-di-GMP) is a second messenger that controls the transition between planktonic and sessile lifestyles, in response to environmental cues. Our study reveals the potential of c-di-GMP to alter the carbon metabolic pathways in S. Typhimurium. Cyclic di-GMP overproduction decreased the transcription of genes that encode components of three phosphoenolpyruvate (PEP):carbohydrate phosphotransferase systems (PTSs) allocated for the uptake of glucose (PTSGlc), mannose (PTSMan), and fructose (PTSFru). PTS gene downregulation by c-di-GMP was alleviated in the absence of the three regulators, SgrS, Mlc, and Cra, suggesting their intermediary roles between c-di-GMP and PTS regulation. Moreover, Cra was found to bind to the promoters of ptsG, manX, and fruB. In contrast, c-di-GMP increased the transcription of genes important for gluconeogenesis. However, this effect of c-di-GMP in gluconeogenesis disappeared in the absence of Cra, indicating that Cra is a pivotal regulator that coordinates the carbon flux between PTS-mediated sugar uptake and gluconeogenesis, in response to cellular c-di-GMP concentrations. Since gluconeogenesis supplies precursor sugars required for extracellular polysaccharide production, Salmonella may exploit c-di-GMP as a dual-purpose signal that rewires carbon flux from glycolysis to gluconeogenesis and promotes biofilm formation using the end products of gluconeogenesis. This study sheds light on a new role for c-di-GMP in modulating carbon flux, to coordinate bacterial behavior in response to hostile environments. IMPORTANCE Cyclic di-GMP is a central signaling molecule that determines the transition between motile and nonmotile lifestyles in many bacteria. It stimulates biofilm formation at high concentrations but leads to biofilm dispersal and planktonic status at low concentrations. This study provides new insights into the role of c-di-GMP in programming carbon metabolic pathways. An increase in c-di-GMP downregulated the expression of PTS genes important for sugar uptake, while simultaneously upregulating the transcription of genes important for bacterial gluconeogenesis. The directly opposing effects of c-di-GMP on sugar metabolism were mediated by Cra (catabolite repressor/activator), a dual transcriptional regulator that modulates the direction of carbon flow. Salmonella may potentially harness c-di-GMP to promote its survival and fitness in hostile environments via the coordination of carbon metabolic pathways and the induction of biofilm formation.
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Affiliation(s)
- Jiwon Baek
- Department of Molecular Science and Technology, Ajou University, Suwon, Republic of Korea
| | - Hyunjin Yoon
- Department of Molecular Science and Technology, Ajou University, Suwon, Republic of Korea
- Department of Applied Chemistry and Biological Engineering, Ajou University, Suwon, Republic of Korea
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5
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El-Mansi M. Control of central metabolism’s architecture in Escherichia coli: An overview. Microbiol Res 2023; 266:127224. [DOI: 10.1016/j.micres.2022.127224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Revised: 10/05/2022] [Accepted: 10/05/2022] [Indexed: 11/06/2022]
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6
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Chen M, Liang H, Han C, Zhou P, Xing Z, Chen Q, Liu Y, Xie GA, Xie R. Engineering of global transcription factor FruR to redirect the carbon flow in Escherichia coli for enhancing L-phenylalanine biosynthesis. Microb Cell Fact 2022; 21:222. [PMID: 36289548 PMCID: PMC9609185 DOI: 10.1186/s12934-022-01954-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Accepted: 10/13/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The catabolite repressor/activator protein (FruR) is a global regulatory protein known to control the expression of several genes concerned with carbon utilization and energy metabolism. This study aimed to illustrate effects of the FruR mutant on the L-phenylalanine (L-PHE) producing strain PHE01. RESULTS Random mutagenesis libraries of fruR generated in vitro were first integrated into the chromosome of PHE01 by CRISPR/Cas9 technique, and then the best mutant PHE07 (FruRE173K) was obtained. With this mutant, a final L-PHE concentration of 70.50 ± 1.02 g/L was achieved, which was 23.34% higher than that of PHE01. To better understand the mechanism, both transcriptomes and metabolomes of PHE07 were carried out and compared to that of PHE01. Specifically, the transcript levels of genes involved in gluconeogenesis pathway, pentose phosphate pathway, Krebs cycle, and glyoxylate shunt were up-regulated in the FruRE173K mutant, whereas genes aceEF, acnB, and icd were down-regulated. From the metabolite level, the FruRE173K mutation led to an accumulation of pentose phosphate pathway and Krebs cycle products, whereas the products of pyruvate metabolism pathway: acetyl-CoA and cis-aconic acid, were down-regulated. As a result of the altered metabolic flows, the utilization of carbon sources was improved and the supply of precursors (phosphoenolpyruvate and erythrose 4-phosphate) for L-PHE biosynthesis was increased, which together led to the enhanced production of L-PHE. CONCLUSION A novel strategy for L-PHE overproduction by modification of the global transcription factor FruR in E. coli was reported. Especially, these findings expand the scope of pathways affected by the fruR regulon and illustrate its importance as a global regulator in L-PHE production.
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Affiliation(s)
- Minliang Chen
- Henan Joincare Biopharma Research Institute Co. Ltd, Jinyuan Street 8, Jiaozuo, 454000 People’s Republic of China ,Guangdong Provincial Key Laboratory of Research and Development and Application of Fermentation and Semi-Synthetic Drugs, Livzon New North River Pharmaceutical Co. Ltd, 1st Renmin Road, Qingyuan, 511500 People’s Republic of China
| | - Hengyu Liang
- Henan Joincare Biopharma Research Institute Co. Ltd, Jinyuan Street 8, Jiaozuo, 454000 People’s Republic of China ,Jiaozuo Joincare Biotechnology Co. Ltd, Jinyuan Street 8, Jiaozuo, 454000 People’s Republic of China ,Guangdong Provincial Key Laboratory of Research and Development and Application of Fermentation and Semi-Synthetic Drugs, Livzon New North River Pharmaceutical Co. Ltd, 1st Renmin Road, Qingyuan, 511500 People’s Republic of China
| | - Chao Han
- Henan Joincare Biopharma Research Institute Co. Ltd, Jinyuan Street 8, Jiaozuo, 454000 People’s Republic of China ,Guangdong Provincial Key Laboratory of Research and Development and Application of Fermentation and Semi-Synthetic Drugs, Livzon New North River Pharmaceutical Co. Ltd, 1st Renmin Road, Qingyuan, 511500 People’s Republic of China
| | - Peng Zhou
- Henan Joincare Biopharma Research Institute Co. Ltd, Jinyuan Street 8, Jiaozuo, 454000 People’s Republic of China ,Guangdong Provincial Key Laboratory of Research and Development and Application of Fermentation and Semi-Synthetic Drugs, Livzon New North River Pharmaceutical Co. Ltd, 1st Renmin Road, Qingyuan, 511500 People’s Republic of China
| | - Zhiwei Xing
- Henan Joincare Biopharma Research Institute Co. Ltd, Jinyuan Street 8, Jiaozuo, 454000 People’s Republic of China ,Jiaozuo Joincare Biotechnology Co. Ltd, Jinyuan Street 8, Jiaozuo, 454000 People’s Republic of China
| | - Qianqian Chen
- Guangdong Provincial Key Laboratory of Research and Development and Application of Fermentation and Semi-Synthetic Drugs, Livzon New North River Pharmaceutical Co. Ltd, 1st Renmin Road, Qingyuan, 511500 People’s Republic of China
| | - Yongyu Liu
- Henan Joincare Biopharma Research Institute Co. Ltd, Jinyuan Street 8, Jiaozuo, 454000 People’s Republic of China
| | - Gou-an Xie
- Henan Joincare Biopharma Research Institute Co. Ltd, Jinyuan Street 8, Jiaozuo, 454000 People’s Republic of China
| | - Rufei Xie
- Henan Joincare Biopharma Research Institute Co. Ltd, Jinyuan Street 8, Jiaozuo, 454000 People’s Republic of China
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Abdelhamed H, Ramachandran R, Narayanan L, Islam S, Ozan O, Freitag N, Lawrence ML. Role of FruR transcriptional regulator in virulence of Listeria monocytogenes and identification of its regulon. PLoS One 2022; 17:e0274005. [PMID: 36054213 PMCID: PMC9439231 DOI: 10.1371/journal.pone.0274005] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Accepted: 08/19/2022] [Indexed: 11/29/2022] Open
Abstract
Listeria monocytogenes is a ubiquitous opportunistic foodborne pathogen capable of survival in various adverse environmental conditions. Pathogenesis of L. monocytogenes is tightly controlled by a complex regulatory network of transcriptional regulators that are necessary for survival and adaptations to harsh environmental conditions both inside and outside host cells. Among these regulatory pathways are members of the DeoR-family transcriptional regulators that are known to play a regulatory role in sugar metabolism. In this study, we deciphered the role of FruR, a DeoR family protein, which is a fructose operon transcriptional repressor protein, in L. monocytogenes pathogenesis and growth. Following intravenous (IV) inoculation in mice, a mutant strain with deletion of fruR exhibited a significant reduction in bacterial burden in liver and spleen tissues compared to the parent strain. Further, the ΔfruR strain had a defect in cell-to-cell spread in L2 fibroblast monolayers. Constitutive activation of PrfA, a pleiotropic activator of L. monocytogenes virulence factors, did not restore virulence to the ΔfruR strain, suggesting that the attenuation was not a result of impaired PrfA activation. Transcriptome analysis revealed that FruR functions as a positive regulator for genes encoding enzymes involved in the pentose phosphate pathway (PPP) and as a repressor for genes encoding enzymes in the glycolysis pathway. These results suggested that FruR may function to facilitate NADPH regeneration, which is necessary for full protection from oxidative stress. Interestingly, deletion of fruR increased sensitivity of L. monocytogenes to H2O2, confirming a role for FruR in survival of L. monocytogenes during oxidative stress. Using anti-mouse neutrophil/monocyte monoclonal antibody RB6-8C5 (RB6) in an in vivo infection model, we found that FruR has a specific function in protecting L. monocytogenes from neutrophil/monocyte-mediated killing. Overall, this work clarifies the role of FruR in controlling L. monocytogenes carbon flow between glycolysis and PPP for NADPH homeostasis, which provides a new mechanism allowing metabolic adaptation of L. monocytogenes to oxidative stress.
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Affiliation(s)
- Hossam Abdelhamed
- Department of Comparative Biomedical Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS, United States of America
- * E-mail:
| | - Reshma Ramachandran
- Department of Comparative Biomedical Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS, United States of America
- Department of Poultry Science, Mississippi State University, Starkville, MS, United States of America
| | - Lakshmi Narayanan
- Department of Comparative Biomedical Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS, United States of America
| | - Shamima Islam
- Department of Comparative Biomedical Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS, United States of America
| | - Ozdemir Ozan
- Department of Comparative Biomedical Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS, United States of America
| | - Nancy Freitag
- Department of Pharmaceutical Sciences, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Mark L. Lawrence
- Department of Comparative Biomedical Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS, United States of America
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Saito S, Imai R, Miyahara Y, Nakagawa M, Orita I, Tsuge T, Fukui T. Biosynthesis of Poly(3-hydroxybutyrate- co-3-hydroxyhexanoate) From Glucose by Escherichia coli Through Butyryl-CoA Formation Driven by Ccr-Emd Combination. Front Bioeng Biotechnol 2022; 10:888973. [PMID: 35646875 PMCID: PMC9134075 DOI: 10.3389/fbioe.2022.888973] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Accepted: 04/11/2022] [Indexed: 11/29/2022] Open
Abstract
Poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate] [P(3HB-co-3HHx)] is a practical kind of bacterial polyhydroxyalkanoates (PHAs). A previous study has established an artificial pathway for the biosynthesis of P(3HB-co-3HHx) from structurally unrelated sugars in Ralstonia eutropha, in which crotonyl-CoA carboxylase/reductase (Ccr) and ethylmalonyl-CoA decarboxylase (Emd) are a key combination for generation of butyryl-CoA and the following chain elongation. This study focused on the installation of the artificial pathway into Escherichia coli. The recombinant strain of E. coli JM109 harboring 11 heterologous genes including Ccr and Emd produced P(3HB-co-3HHx) composed of 14 mol% 3HHx with 41 wt% of dry cellular weight from glucose. Further investigations revealed that the C6 monomer (R)-3HHx-CoA was not supplied by (R)-specific reduction of 3-oxohexanoyl-CoA but by (R)-specific hydration of 2-hexenoyl-CoA formed through reverse β-oxidation after the elongation from C4 to C6. While contribution of the reverse β-oxidation to the conversion of the C4 intermediates was very limited, crotonyl-CoA, a precursor of butyryl-CoA, was generated by dehydration of (R)-3HB-CoA. Several modifications previously reported for enhancement of bioproduction in E. coli were examined for the copolyester synthesis. Elimination of the global regulator Cra or PdhR as well as the block of acetate formation resulted in poor PHA synthesis. The strain lacking RNase G accumulated more PHA but with almost no 3HHx unit. Introduction of the phosphite oxidation system for regeneration of NADPH led to copolyester synthesis with the higher cellular content and higher 3HHx composition by two-stage cultivation with phosphite than those in the absence of phosphite.
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Affiliation(s)
- Shu Saito
- School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
| | - Ryu Imai
- School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
| | - Yuki Miyahara
- School of Materials and Chemical Technology, Tokyo Institute of Technology, Yokohama, Japan
| | - Mari Nakagawa
- School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
| | - Izumi Orita
- School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
| | - Takeharu Tsuge
- School of Materials and Chemical Technology, Tokyo Institute of Technology, Yokohama, Japan
| | - Toshiaki Fukui
- School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
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9
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Liu X, Zhao G, Sun S, Fan C, Feng X, Xiong P. Biosynthetic Pathway and Metabolic Engineering of Succinic Acid. Front Bioeng Biotechnol 2022; 10:843887. [PMID: 35350186 PMCID: PMC8957974 DOI: 10.3389/fbioe.2022.843887] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Accepted: 02/16/2022] [Indexed: 11/25/2022] Open
Abstract
Succinic acid, a dicarboxylic acid produced as an intermediate of the tricarboxylic acid (TCA) cycle, is one of the most important platform chemicals for the production of various high value-added derivatives. As traditional chemical synthesis processes suffer from nonrenewable resources and environment pollution, succinic acid biosynthesis has drawn increasing attention as a viable, more environmentally friendly alternative. To date, several metabolic engineering approaches have been utilized for constructing and optimizing succinic acid cell factories. In this review, different succinic acid biosynthesis pathways are summarized, with a focus on the key enzymes and metabolic engineering approaches, which mainly include redirecting carbon flux, balancing NADH/NAD+ ratios, and optimizing CO2 supplementation. Finally, future perspectives on the microbial production of succinic acid are discussed.
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Affiliation(s)
- Xiutao Liu
- School of Life Sciences and Medicine, Shandong University of Technology, Zibo, China
| | - Guang Zhao
- State Key Lab of Microbial Technology, Shandong University, Qingdao, China
| | - Shengjie Sun
- School of Life Sciences and Medicine, Shandong University of Technology, Zibo, China
| | - Chuanle Fan
- CAS Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, China.,School of Chemical Engineering, University of Chinese Academy of Sciences, Beijing, China
| | - Xinjun Feng
- CAS Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, China
| | - Peng Xiong
- School of Life Sciences and Medicine, Shandong University of Technology, Zibo, China
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10
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Schink SJ, Christodoulou D, Mukherjee A, Athaide E, Brunner V, Fuhrer T, Bradshaw GA, Sauer U, Basan M. Glycolysis/gluconeogenesis specialization in microbes is driven by biochemical constraints of flux sensing. Mol Syst Biol 2022; 18:e10704. [PMID: 34994048 PMCID: PMC8738977 DOI: 10.15252/msb.202110704] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Revised: 12/10/2021] [Accepted: 12/14/2021] [Indexed: 11/29/2022] Open
Abstract
Central carbon metabolism is highly conserved across microbial species, but can catalyze very different pathways depending on the organism and their ecological niche. Here, we study the dynamic reorganization of central metabolism after switches between the two major opposing pathway configurations of central carbon metabolism, glycolysis, and gluconeogenesis in Escherichia coli, Pseudomonas aeruginosa, and Pseudomonas putida. We combined growth dynamics and dynamic changes in intracellular metabolite levels with a coarse-grained model that integrates fluxes, regulation, protein synthesis, and growth and uncovered fundamental limitations of the regulatory network: After nutrient shifts, metabolite concentrations collapse to their equilibrium, rendering the cell unable to sense which direction the flux is supposed to flow through the metabolic network. The cell can partially alleviate this by picking a preferred direction of regulation at the expense of increasing lag times in the opposite direction. Moreover, decreasing both lag times simultaneously comes at the cost of reduced growth rate or higher futile cycling between metabolic enzymes. These three trade-offs can explain why microorganisms specialize for either glycolytic or gluconeogenic substrates and can help elucidate the complex growth patterns exhibited by different microbial species.
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Affiliation(s)
| | - Dimitris Christodoulou
- Systems Biology DepartmentHarvard Medical SchoolBostonMAUSA
- Institute of Molecular Systems BiologyETH ZurichZurichSwitzerland
| | - Avik Mukherjee
- Systems Biology DepartmentHarvard Medical SchoolBostonMAUSA
- Applied Mathematics DepartmentHarvard CollegeCambridgeMAUSA
| | - Edward Athaide
- Applied Mathematics DepartmentHarvard CollegeCambridgeMAUSA
| | - Viktoria Brunner
- Institute of Molecular Systems BiologyETH ZurichZurichSwitzerland
| | - Tobias Fuhrer
- Institute of Molecular Systems BiologyETH ZurichZurichSwitzerland
| | - Gary Andrew Bradshaw
- Laboratory of Systems PharmacologyHarvard Program in Therapeutic ScienceHarvard Medical SchoolBostonMAUSA
| | - Uwe Sauer
- Institute of Molecular Systems BiologyETH ZurichZurichSwitzerland
| | - Markus Basan
- Systems Biology DepartmentHarvard Medical SchoolBostonMAUSA
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11
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Zhu Y, Li Y, Xu Y, Zhang J, Ma L, Qi Q, Wang Q. Development of bifunctional biosensors for sensing and dynamic control of glycolysis flux in metabolic engineering. Metab Eng 2021; 68:142-151. [PMID: 34610458 DOI: 10.1016/j.ymben.2021.09.011] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 09/30/2021] [Accepted: 09/30/2021] [Indexed: 11/30/2022]
Abstract
Glycolysis is the primary metabolic pathway in all living organisms. Maintaining the balance of glycolysis flux and biosynthetic pathways is the crucial matter involved in the microbial cell factory. Few regulation systems can address the issue of metabolic flux imbalance in glycolysis. Here, we designed and constructed a bifunctional glycolysis flux biosensor that can dynamically regulate glycolysis flux for overproduction of desired biochemicals. A series of positive-and negative-response biosensors were created and modified for varied thresholds and dynamic ranges. These engineered glycolysis flux biosensors were verified to be able to characterize in vivo fructose-1,6-diphosphate concentration. Subsequently, the biosensors were applied for fine-tuning glycolysis flux to effectively balance the biosynthesis of two chemicals: mevalonate and N-acetylglucosamine. A glycolysis flux-dynamically controlled Escherichia coli strain achieved a 111.3 g/L mevalonate titer in a 1L fermenter.
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Affiliation(s)
- Yuan Zhu
- National Glycoengineering Research Center, State Key Laboratory of Microbial Technology, Shandong University, Qingdao, 266237, PR China
| | - Ying Li
- National Glycoengineering Research Center, State Key Laboratory of Microbial Technology, Shandong University, Qingdao, 266237, PR China
| | - Ya Xu
- National Glycoengineering Research Center, State Key Laboratory of Microbial Technology, Shandong University, Qingdao, 266237, PR China
| | - Jian Zhang
- National Glycoengineering Research Center, State Key Laboratory of Microbial Technology, Shandong University, Qingdao, 266237, PR China
| | - Linlin Ma
- National Glycoengineering Research Center, State Key Laboratory of Microbial Technology, Shandong University, Qingdao, 266237, PR China
| | - Qingsheng Qi
- National Glycoengineering Research Center, State Key Laboratory of Microbial Technology, Shandong University, Qingdao, 266237, PR China; CAS Key Lab of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, PR China.
| | - Qian Wang
- National Glycoengineering Research Center, State Key Laboratory of Microbial Technology, Shandong University, Qingdao, 266237, PR China.
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12
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Liu L, Bilal M, Luo H, Iqbal HMN. Impact of Transcriptional Regulation by Crp, FruR, FlhD, and TyrR on L-tryptophan Biosynthesis in Escherichia coli. APPL BIOCHEM MICRO+ 2021. [DOI: 10.1134/s0003683821030091] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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13
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Cra and cAMP Receptor Protein Have Opposing Roles in the Regulation of fruB in Vibrio cholerae. J Bacteriol 2021; 203:JB.00044-21. [PMID: 33649152 PMCID: PMC8088597 DOI: 10.1128/jb.00044-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Accepted: 02/23/2021] [Indexed: 11/20/2022] Open
Abstract
Vibrio cholerae is the causative agent of cholera disease. While current treatments of care are accessible, we still lack an understanding of the molecular mechanisms that allow V. cholerae to survive in both aquatic reservoirs and the human small intestine, where pathogenesis occurs. The Gram-negative bacterium Vibrio cholerae adapts to changes in the environment by selectively producing the necessary machinery to take up and metabolize available carbohydrates. The import of fructose by the fructose-specific phosphoenolpyruvate (PEP) phosphotransferase system (PTS) is of particular interest because of its putative connection to cholera pathogenesis and persistence. Here, we describe the expression and regulation of fruB, which encodes an EIIA-FPr fusion protein as part of the fructose-specific PTS in V. cholerae. Using a series of transcriptional reporter fusions and additional biochemical and genetic assays, we identified Cra (catabolite repressor/activator) and cAMP receptor protein (CRP) as regulators of fruB expression and determined that this regulation is dependent upon the presence or absence of PTS sugars. Cra functions as a repressor, downregulating fruB expression in the absence of fructose when components of PTSFru are not needed. CRP functions as an activator of fruB expression. We also report that Cra and CRP can affect fruB expression independently; however, CRP can modulate cra expression in the presence of fructose and glucose. Evidence from this work provides the foundation for continued investigations into PTSFru and its relationship to the V. cholerae life cycle. IMPORTANCEVibrio cholerae is the causative agent of cholera disease. While current treatments of care are accessible, we still lack an understanding of the molecular mechanisms that allow V. cholerae to survive in both aquatic reservoirs and the human small intestine, where pathogenesis occurs. Central to V. cholerae’s survival is its ability to use available carbon sources. Here, we investigate the regulation of fruB, which encodes a protein central to the import and metabolism of fructose. We show that fruB expression is controlled by the transcriptional regulators Cra and CRP. This work contributes toward a clearer understanding of how carbon source availability impacts the physiology and, potentially, the persistence of the pathogen.
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14
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Yoon CK, Kang D, Kim MK, Seok YJ. Vibrio cholerae FruR facilitates binding of RNA polymerase to the fru promoter in the presence of fructose 1-phosphate. Nucleic Acids Res 2021; 49:1397-1410. [PMID: 33476373 PMCID: PMC7897506 DOI: 10.1093/nar/gkab013] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 12/31/2020] [Accepted: 01/06/2021] [Indexed: 12/25/2022] Open
Abstract
In most bacteria, efficient use of carbohydrates is primarily mediated by the phosphoenolpyruvate (PEP):carbohydrate phosphotransferase system (PTS), which concomitantly phosphorylates the substrates during import. Therefore, transcription of the PTS-encoding genes is precisely regulated by transcriptional regulators, depending on the availability of the substrate. Fructose is transported mainly through the fructose-specific PTS (PTSFru) and simultaneously converted into fructose 1-phosphate (F1P). In Gammaproteobacteria such as Escherichia coli and Pseudomonas putida, transcription of the fru operon encoding two PTSFru components, FruA and FruB, and the 1-phosphofructokinase FruK is repressed by FruR in the absence of the inducer F1P. Here, we show that, contrary to the case in other Gammaproteobacteria, FruR acts as a transcriptional activator of the fru operon and is indispensable for the growth of Vibrio cholerae on fructose. Several lines of evidence suggest that binding of the FruR-F1P complex to an operator which is located between the –35 and –10 promoter elements changes the DNA structure to facilitate RNA polymerase binding to the promoter. We discuss the mechanism by which the highly conserved FruR regulates the expression of its target operon encoding the highly conserved PTSFru and FruK in a completely opposite direction among closely related families of bacteria.
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Affiliation(s)
- Chang-Kyu Yoon
- School of Biological Sciences and Institute of Microbiology, Seoul National University, Seoul 08826, Korea
| | - Deborah Kang
- School of Biological Sciences and Institute of Microbiology, Seoul National University, Seoul 08826, Korea
| | - Min-Kyu Kim
- Radiation Research Division, Korea Atomic Energy Research Institute, Jeongeup 56212, Korea
| | - Yeong-Jae Seok
- School of Biological Sciences and Institute of Microbiology, Seoul National University, Seoul 08826, Korea
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15
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Sander KB, Chung D, Klingeman DM, Giannone RJ, Rodriguez M, Whitham J, Hettich RL, Davison BH, Westpheling J, Brown SD. Gene targets for engineering osmotolerance in Caldicellulosiruptor bescii. BIOTECHNOLOGY FOR BIOFUELS 2020; 13:50. [PMID: 32190115 PMCID: PMC7071700 DOI: 10.1186/s13068-020-01690-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Accepted: 02/27/2020] [Indexed: 05/05/2023]
Abstract
BACKGROUND Caldicellulosiruptor bescii, a promising biocatalyst being developed for use in consolidated bioprocessing of lignocellulosic materials to ethanol, grows poorly and has reduced conversion at elevated medium osmolarities. Increasing tolerance to elevated fermentation osmolarities is desired to enable performance necessary of a consolidated bioprocessing (CBP) biocatalyst. RESULTS Two strains of C. bescii showing growth phenotypes in elevated osmolarity conditions were identified. The first strain, ORCB001, carried a deletion of the FapR fatty acid biosynthesis and malonyl-CoA metabolism repressor and had a severe growth defect when grown in high-osmolarity conditions-introduced as the addition of either ethanol, NaCl, glycerol, or glucose to growth media. The second strain, ORCB002, displayed a growth rate over three times higher than its genetic parent when grown in high-osmolarity medium. Unexpectedly, a genetic complement ORCB002 exhibited improved growth, failing to revert the observed phenotype, and suggesting that mutations other than the deleted transcription factor (the fruR/cra gene) are responsible for the growth phenotype observed in ORCB002. Genome resequencing identified several other genomic alterations (three deleted regions, three substitution mutations, one silent mutation, and one frameshift mutation), which may be responsible for the observed increase in osmolarity tolerance in the fruR/cra-deficient strain, including a substitution mutation in dnaK, a gene previously implicated in osmoresistance in bacteria. Differential expression analysis and transcription factor binding site inference indicates that FapR negatively regulates malonyl-CoA and fatty acid biosynthesis, as it does in many other bacteria. FruR/Cra regulates neighboring fructose metabolism genes, as well as other genes in global manner. CONCLUSIONS Two systems able to effect tolerance to elevated osmolarities in C. bescii are identified. The first is fatty acid biosynthesis. The other is likely the result of one or more unintended, secondary mutations present in another transcription factor deletion strain. Though the locus/loci and mechanism(s) responsible remain unknown, candidate mutations are identified, including a mutation in the dnaK chaperone coding sequence. These results illustrate both the promise of targeted regulatory manipulation for osmotolerance (in the case of fapR) and the challenges (in the case of fruR/cra).
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Affiliation(s)
- Kyle B. Sander
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
- Bredesen Center for Interdisciplinary Graduate Research and Education, University of Tennessee, Knoxville, TN USA
- Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, TN USA
- Present Address: Department of Bioengineering, University of California, Berkeley, Berkeley, CA USA
| | - Daehwan Chung
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
- Department of Genetics, University of Georgia, Athens, GA USA
- Present Address: National Bioenergy Center, National Renewable Energy Laboratory, Golden, CO USA
| | - Dawn M. Klingeman
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
| | - Richard J. Giannone
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
| | - Miguel Rodriguez
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
| | - Jason Whitham
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
- Present Address: Becton Dickinson Diagnostics, Sparks Glencoe, MD USA
| | - Robert L. Hettich
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
| | - Brian H. Davison
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
- Bredesen Center for Interdisciplinary Graduate Research and Education, University of Tennessee, Knoxville, TN USA
- Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, TN USA
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
| | - Janet Westpheling
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
- Department of Genetics, University of Georgia, Athens, GA USA
| | - Steven D. Brown
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
- Bredesen Center for Interdisciplinary Graduate Research and Education, University of Tennessee, Knoxville, TN USA
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
- Present Address: LanzaTech, Skokie, IL USA
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16
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El-Mansi M. Contrasting effects of isocitrate dehydrogenase deletion on fluxes through enzymes of central metabolism in Escherichia coli. FEMS Microbiol Lett 2019; 366:5556941. [DOI: 10.1093/femsle/fnz187] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Accepted: 08/29/2019] [Indexed: 12/15/2022] Open
Abstract
ABSTRACTFlux analysis is central to understanding cellular metabolism and successful manipulation of metabolic fluxes in microbial cell-factories. Isocitrate dehydrogenase (ICDH) deletion conferred contrasting effects on fluxes through substrate-level phosphorylation (SLP) reactions. While significantly increasing flux through pyruvate kinase, it diminishes flux through succinyl CoA synthetase and upregulates phosphotransacetylase (PTA) and acetate kinase (AK). In addition to acetate, the ICDH-less strain excretes pyruvate, citrate and isocitrate. While efflux to acetate excretion by the Escherichia coli parental strain and its ICDH-less derivative is a reflection of high throughput of glycolytic intermediates, excretion of pyruvate is a reflection of high throughput via pyruvate kinase. On the other hand, citrate and isocitrate excretion is a reflection of truncating the Krebs cycle at the level of ICDH. Furthermore, another striking finding is the inability of the ICDH-less cultures to utilize acetate as a source of carbon despite the availability of an adequate supply of extracellular glutamate (for biosynthesis) and elevated levels of AK and PTA (for acetate uptake). This striking observation is now explicable in the light of the newly proposed hypothesis that the expression of the ace operon enzymes is controlled in response to a minimum threshold signal (ATP), which could not be achieved in the ICDH-less strain.
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Affiliation(s)
- Mansi El-Mansi
- Elizade University, Ilara Mokin, Ondo State, Nigeria
- University of Africa (UAT), Bayelsa State, Nigeria
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17
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Metabolic Engineering and Fermentation Process Strategies for L-Tryptophan Production by Escherichia coli. Processes (Basel) 2019. [DOI: 10.3390/pr7040213] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
L-tryptophan is an essential aromatic amino acid that has been widely used in medicine, food, and animal feed. Microbial biosynthesis of L-tryptophan through metabolic engineering approaches represents a sustainable, cost-effective, and environmentally friendly route compared to chemical synthesis. In particular, metabolic pathway engineering allows enhanced product titers by inactivating/blocking the competing pathways, increasing the intracellular level of essential precursors, and overexpressing rate-limiting enzymatic steps. Based on the route of the l-tryptophan biosynthesis pathway, this review presents a systematic and detailed summary of the contemporary metabolic engineering approaches employed for l-tryptophan production. In addition to the engineering of the l-tryptophan biosynthesis pathway, the metabolic engineering modification of carbon source uptake, by-product formation, key regulatory factors, and the polyhydroxybutyrate biosynthesis pathway in l-tryptophan biosynthesis are discussed. Moreover, fermentation bioprocess optimization strategies used for l-tryptophan overproduction are also delineated. Towards the end, the review is wrapped up with the concluding remarks, and future strategies are outlined for the development of a high l-tryptophan production strain.
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18
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Bley Folly B, Ortega AD, Hubmann G, Bonsing-Vedelaar S, Wijma HJ, van der Meulen P, Milias-Argeitis A, Heinemann M. Assessment of the interaction between the flux-signaling metabolite fructose-1,6-bisphosphate and the bacterial transcription factors CggR and Cra. Mol Microbiol 2018; 109:278-290. [DOI: 10.1111/mmi.14008] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/13/2018] [Indexed: 01/21/2023]
Affiliation(s)
- Brenda Bley Folly
- Molecular Systems Biology, Groningen Biomolecular Sciences and Biotechnology Institute; University of Groningen; Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Alvaro D. Ortega
- Molecular Systems Biology, Groningen Biomolecular Sciences and Biotechnology Institute; University of Groningen; Nijenborgh 4 9747 AG Groningen The Netherlands
- Department of Cell Biology, Faculty of Biology; Complutense University of Madrid; José Antonio Nováis 12 28040 Madrid Spain
| | - Georg Hubmann
- Molecular Systems Biology, Groningen Biomolecular Sciences and Biotechnology Institute; University of Groningen; Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Silke Bonsing-Vedelaar
- Molecular Systems Biology, Groningen Biomolecular Sciences and Biotechnology Institute; University of Groningen; Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Hein J. Wijma
- Biotechnology, Groningen Biomolecular Sciences and Biotechnology Institute; University of Groningen; Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Pieter van der Meulen
- Stratingh Institute for Chemistry; University of Groningen; Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Andreas Milias-Argeitis
- Molecular Systems Biology, Groningen Biomolecular Sciences and Biotechnology Institute; University of Groningen; Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Matthias Heinemann
- Molecular Systems Biology, Groningen Biomolecular Sciences and Biotechnology Institute; University of Groningen; Nijenborgh 4 9747 AG Groningen The Netherlands
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19
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Chavarría M, de Lorenzo V. The imbroglio of the physiological Cra effector clarified at last. Mol Microbiol 2018; 109:273-277. [PMID: 30019355 DOI: 10.1111/mmi.14080] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/10/2018] [Indexed: 11/29/2022]
Abstract
Owing to its role in controlling carbon and energy metabolism, the catabolite repressor/activator protein Cra has been one of the most studied prokaryotic regulators of the last 30 years. Yet, a key mechanistic detail of its biological function - i.e. the nature of the metabolic effector that rules its DNA-binding ability - has remained controversial. Despite the high affinity of Cra for fructose-1-phosphate (F1P), the prevailing view claimed that fructose-1,6-biphosphate (FBP) was the key physiological effector. Building on such responsiveness to FBP, Cra was proposed to act as a glycolytic flux sensor and central regulator of critical metabolic transactions. At the same time, data raised on the Cra protein of Pseudomonas putida ruled out that FBP could be an effector - but instead suggested that it was the unintentional carrier of a small contamination by F1P, the actual signal molecule. While these data on the P. putida Cra were received with skepticism - if not dismissal - by the community of the time, the paper by (Bley-Folly et al, 2018) now demonstrates beyond any reasonable doubt that the one and only effector of E. coli Cra is F1P and that every action of FBP on this regulator can be traced to its systematic mix with the authentic binder.
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Affiliation(s)
- Max Chavarría
- Escuela de Química & CIPRONA, Universidad de Costa Rica, San José, 11501-2060, Costa Rica.,Centro Nacional de Innovaciones Biotecnológicas (CENIBiot), CeNAT-CONARE, San José, 1174-1200, Costa Rica
| | - Víctor de Lorenzo
- Systems and Synthetic Biology Program, Centro Nacional de Biotecnología (CNB-CSIC), Campus Cantoblanco, Madrid, 28049, Spain
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20
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Fernández-Coll L, Cashel M. Contributions of SpoT Hydrolase, SpoT Synthetase, and RelA Synthetase to Carbon Source Diauxic Growth Transitions in Escherichia coli. Front Microbiol 2018; 9:1802. [PMID: 30123210 PMCID: PMC6085430 DOI: 10.3389/fmicb.2018.01802] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Accepted: 07/17/2018] [Indexed: 12/22/2022] Open
Abstract
During the diauxic shift, Escherichia coli exhausts glucose and adjusts its expression pattern to grow on a secondary carbon source. Transcriptional profiling studies of glucose–lactose diauxic transitions reveal a key role for ppGpp. The amount of ppGpp depends on RelA synthetase and the balance between a strong SpoT hydrolase and its weak synthetase. In this study, mutants are used to search for synthetase or hydrolase specific regulation. Diauxic shifts experiments were performed with strains containing SpoT hydrolase and either RelA or SpoT synthetase as the sole source of ppGpp. Here, the length of the diauxic lag times is determined by the presence of ppGpp, showing contributions of both ppGpp synthetases (RelA and SpoT) as well as its hydrolase (SpoT). A balanced ppGpp response is key for a proper adaptation during diauxic shift. The effects of one or the other ppGpp synthetase on diauxic shifts are abolished by addition of amino acids or succinate, although by different mechanisms. While amino acids control the RelA response, succinate blocks the uptake of the excreted acetate via SatP. Acetate is converted to Acetyl-CoA through the ackA-pta pathway, producing Ac-P as intermediate. Evidence of control of the ackA-pta operon as well as a correlation between ppGpp and Ac-P is shown. Finally, acetylation of proteins is shown to occur during a diauxic glucose–lactose shift.
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Affiliation(s)
- Llorenç Fernández-Coll
- Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States
| | - Michael Cashel
- Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States
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21
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The Catabolite Repressor/Activator Cra Is a Bridge Connecting Carbon Metabolism and Host Colonization in the Plant Drought Resistance-Promoting Bacterium Pantoea alhagi LTYR-11Z. Appl Environ Microbiol 2018; 84:AEM.00054-18. [PMID: 29703735 DOI: 10.1128/aem.00054-18] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Accepted: 04/20/2018] [Indexed: 12/22/2022] Open
Abstract
Efficient root colonization is a prerequisite for application of plant growth-promoting (PGP) bacteria in improving health and yield of agricultural crops. We have recently identified an endophytic bacterium, Pantoea alhagi LTYR-11Z, with multiple PGP properties that effectively colonizes the root system of wheat and improves its growth and drought tolerance. To identify novel regulatory genes required for wheat colonization, we screened an LTYR-11Z transposon (Tn) insertion library and found cra to be a colonization-related gene. By using transcriptome (RNA-seq) analysis, we found that transcriptional levels of an eps operon, the ydiV gene encoding an anti-FlhD4C2 factor, and the yedQ gene encoding an enzyme for synthesis of cyclic dimeric GMP (c-di-GMP) were significantly downregulated in the Δcra mutant. Further studies demonstrated that Cra directly binds to the promoters of the eps operon, ydiV, and yedQ and activates their expression, thus inhibiting motility and promoting exopolysaccharide (EPS) production and biofilm formation. Consistent with previous findings that Cra plays a role in transcriptional regulation in response to carbon source availability, the activating effects of Cra were much more pronounced when LTYR-11Z was grown within a gluconeogenic environment than when it was grown within a glycolytic environment. We further demonstrate that the ability of LTYR-11Z to colonize wheat roots is modulated by the availability of carbon sources. Altogether, these results uncover a novel strategy utilized by LTYR-11Z to achieve host colonization in response to carbon nutrition in the environment, in which Cra bridges a connection between carbon metabolism and colonization capacity of LTYR-11Z.IMPORTANCE Rapid and appropriate response to environmental signals is crucial for bacteria to adapt to competitive environments and to establish interactions with their hosts. Efficient colonization and persistence within the host are controlled by various regulatory factors that respond to specific environmental cues. The most common is nutrient availability. In this work, we unraveled the pivotal role of Cra in regulation of colonization ability of Pantoea alhagi LTYR-11Z in response to carbon source availability. Moreover, we identified three novel members of the Cra regulon involved in EPS synthesis, regulation of flagellar biosynthesis, and synthesis of c-di-GMP and propose a working model to explain the Cra-mediated regulatory mechanism that links carbon metabolism to host colonization. This study elucidates the regulatory role of Cra in bacterial attachment and colonization of plants, which raises the possibility of extending our studies to other bacteria associated with plant and human health.
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22
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Kim D, Seo SW, Gao Y, Nam H, Guzman GI, Cho BK, Palsson BO. Systems assessment of transcriptional regulation on central carbon metabolism by Cra and CRP. Nucleic Acids Res 2018; 46:2901-2917. [PMID: 29394395 PMCID: PMC5888115 DOI: 10.1093/nar/gky069] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Revised: 01/21/2018] [Accepted: 01/24/2018] [Indexed: 12/18/2022] Open
Abstract
Two major transcriptional regulators of carbon metabolism in bacteria are Cra and CRP. CRP is considered to be the main mediator of catabolite repression. Unlike for CRP, in vivo DNA binding information of Cra is scarce. Here we generate and integrate ChIP-exo and RNA-seq data to identify 39 binding sites for Cra and 97 regulon genes that are regulated by Cra in Escherichia coli. An integrated metabolic-regulatory network was formed by including experimentally-derived regulatory information and a genome-scale metabolic network reconstruction. Applying analysis methods of systems biology to this integrated network showed that Cra enables optimal bacterial growth on poor carbon sources by redirecting and repressing glycolysis flux, by activating the glyoxylate shunt pathway, and by activating the respiratory pathway. In these regulatory mechanisms, the overriding regulatory activity of Cra over CRP is fundamental. Thus, elucidation of interacting transcriptional regulation of core carbon metabolism in bacteria by two key transcription factors was possible by combining genome-wide experimental measurement and simulation with a genome-scale metabolic model.
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Affiliation(s)
- Donghyuk Kim
- Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093, USA
- Department of Genetic Engineering, College of Life Sciences, Kyung Hee University, Yongin 446–701, Republic of Korea
| | - Sang Woo Seo
- Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093, USA
- School of Chemical and Biological Engineering, Institute of Chemical Prcocess, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea
| | - Ye Gao
- Division of Biological Science, University of California, San Diego, La Jolla, CA 92093, USA
| | - Hojung Nam
- School of Information and Communication, Gwangju Institute of Science and Technology, 123 Cheomdan-gwagiro, Buk-gu, Gwangju, Republic of Korea
| | - Gabriela I Guzman
- Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093, USA
| | - Byung-Kwan Cho
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
- The Novo Nordisk Foundation Center for Biosustainabiliy, Danish Technical University, 6 Kogle Alle, Hørsholm, Denmark
| | - 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 Biosustainabiliy, Danish Technical University, 6 Kogle Alle, Hørsholm, Denmark
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23
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Basan M. Resource allocation and metabolism: the search for governing principles. Curr Opin Microbiol 2018; 45:77-83. [PMID: 29544124 DOI: 10.1016/j.mib.2018.02.008] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Revised: 01/30/2018] [Accepted: 02/19/2018] [Indexed: 11/28/2022]
Abstract
Elucidating strategies of resource allocation and metabolism is crucial for a better understanding of microbial phenotypes. In particular, uncovering the governing principles underlying these processes would be a crucial step for achieving a central aim of systems microbiology, which is to quantitatively predict phenotypes of microbial cells or entire populations in diverse conditions. Here, some of the key concepts for understanding cellular resource allocation and metabolism that have been suggested over the past years are reviewed. In particular, recent experimental studies that have shown how phenotypic patterns from orthogonal genetic and environmental perturbations can help to differentiate between competing hypotheses and their respective predictions are discussed. Phenomenological models have proven to be a valuable addition to genome-scale models, capable of making quantitative predictions with only few parameters and having aided the identification of molecular mechanisms.
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Affiliation(s)
- Markus Basan
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA.
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24
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Goh EB, Chen Y, Petzold CJ, Keasling JD, Beller HR. Improving methyl ketone production in Escherichia coli by heterologous expression of NADH-dependent FabG. Biotechnol Bioeng 2018; 115:1161-1172. [PMID: 29411856 DOI: 10.1002/bit.26558] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Revised: 01/22/2018] [Accepted: 01/31/2018] [Indexed: 11/07/2022]
Abstract
We previously engineered Escherichia coli to overproduce medium- to long-chain saturated and monounsaturated methyl ketones, which could potentially be applied as diesel fuel blending agents or in the flavor and fragrance industry. Recent efforts at strain optimization have focused on cofactor balance, as fatty acid-derived pathways face the systematic metabolic challenge of net NADPH consumption (in large part, resulting from the key fatty acid biosynthetic enzyme FabG [β-ketoacyl-ACP reductase]) and net NADH production. In this study, we attempted to mitigate cofactor imbalance by heterologously expressing NADH-dependent, rather than NADPH-dependent, versions of FabG identified in previous studies. Of the four NADH-dependent versions of FabG tested in our previously best-reported methyl ketone-producing strain (EGS1895), the version from Acholeplasma laidlawii (Al_FabG) showed the greatest increase in methyl ketone yield in shake flasks (35-75% higher than for an RFP negative-control strain, depending on sugar loading). An improved strain (EGS2920) attained methyl ketone titers during fed-batch fermentation of 5.4 ± 0.5 g/L, which were, on average, ca. 40% greater than those for the base strain (EGS1895) under fermentation conditions optimized in this study. Shotgun proteomic data for strains EGS2920 and EGS1895 during fed-batch fermentation were consistent with the goal of alleviating NADPH limitation through expression of Al_FabG. For example, relative to strain EGS1895, strain EGS2920 significantly upregulated glucose-6-phosphate isomerase (directing flux into glycolysis rather than the NADPH-producing pentose phosphate pathway) and downregulated MaeB (a NADP+ -dependent malate dehydrogenase). Overall, the results suggest that heterologous expression of NADH-dependent FabG in E. coli may improve sustained production of fatty acid-derived renewable fuels and chemicals.
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Affiliation(s)
- Ee-Been Goh
- Joint BioEnergy Institute (JBEI), Emeryville, California.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California
| | - Yan Chen
- Joint BioEnergy Institute (JBEI), Emeryville, California.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California
| | - Christopher J Petzold
- Joint BioEnergy Institute (JBEI), Emeryville, California.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California
| | - Jay D Keasling
- Joint BioEnergy Institute (JBEI), Emeryville, California.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California.,Departments of Chemical and Biomolecular Engineering and of Bioengineering, University of California, Berkeley, California.,The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kogle Allee, Hørsholm, Denmark
| | - Harry R Beller
- Joint BioEnergy Institute (JBEI), Emeryville, California.,Earth and Environmental Sciences, Lawrence Berkeley National Laboratory, Berkeley, California
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25
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Abstract
Enteric pathogens with low infectious doses rely on the ability to orchestrate the expression of virulence and metabolism-associated genes in response to environmental cues for successful infection. Accordingly, the human pathogen enterohemorrhagic Escherichia coli (EHEC) employs a complex multifaceted regulatory network to link the expression of type III secretion system (T3SS) components to nutrient availability. While phosphorylation of histidine and aspartate residues on two-component system response regulators is recognized as an integral part of bacterial signaling, the involvement of phosphotyrosine-mediated control is minimally explored in Gram-negative pathogens. Our recent phosphotyrosine profiling study of E. coli identified 342 phosphorylated proteins, indicating that phosphotyrosine modifications in bacteria are more prevalent than previously anticipated. The present study demonstrates that tyrosine phosphorylation of a metabolite-responsive LacI/GalR family regulator, Cra, negatively affects T3SS expression under glycolytic conditions that are typical for the colonic lumen environment where production of the T3SS is unnecessary. Our data suggest that Cra phosphorylation affects T3SS expression by modulating the expression of ler, which encodes the major activator of EHEC virulence gene expression. Phosphorylation of the Cra Y47 residue diminishes DNA binding to fine-tune the expression of virulence-associated genes, including those of the locus of enterocyte effacement pathogenicity island that encode the T3SS, and thereby negatively affects the formation of attaching and effacing lesions. Our data indicate that tyrosine phosphorylation provides an additional mechanism to control the DNA binding of Cra and other LacI/GalR family regulators, including LacI and PurR. This study describes an initial effort to unravel the role of global phosphotyrosine signaling in the control of EHEC virulence potential. Enterohemorrhagic Escherichia coli (EHEC) causes outbreaks of hemorrhagic colitis and the potentially fatal hemolytic-uremic syndrome. Successful host colonization by EHEC relies on the ability to coordinate the expression of virulence factors in response to environmental cues. A complex network that integrates environmental signals at multiple regulatory levels tightly controls virulence gene expression. We demonstrate that EHEC utilizes a previously uncharacterized phosphotyrosine signaling pathway through Cra to fine-tune the expression of virulence-associated genes to effectively control T3SS production. This study demonstrates that tyrosine phosphorylation negatively affects the DNA-binding capacity of Cra, which affects the expression of genes related to virulence and metabolism. We demonstrate for the first time that phosphotyrosine-mediated control affects global transcription in EHEC. Our data provide insight into a hitherto unexplored regulatory level of the global network controlling EHEC virulence gene expression.
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The Production of Curli Amyloid Fibers Is Deeply Integrated into the Biology of Escherichia coli. Biomolecules 2017; 7:biom7040075. [PMID: 29088115 PMCID: PMC5745457 DOI: 10.3390/biom7040075] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Revised: 10/13/2017] [Accepted: 10/23/2017] [Indexed: 12/29/2022] Open
Abstract
Curli amyloid fibers are the major protein component of the extracellular matrix produced by Enterobacteriaceae during biofilm formation. Curli are required for proper biofilm development and environmental persistence by Escherichia coli. Here, we present a complete and vetted genetic analysis of functional amyloid fiber biogenesis. The Keio collection of single gene deletions was screened on Congo red indicator plates to identify E. coli mutants that had defective amyloid production. We discovered that more than three hundred gene products modulated curli production. These genes were involved in fundamental cellular processes such as regulation, environmental sensing, respiration, metabolism, cell envelope biogenesis, transport, and protein turnover. The alternative sigma factors, σS and σE, had opposing roles in curli production. Mutations that induced the σE or Cpx stress response systems had reduced curli production, while mutant strains with increased σS levels had increased curli production. Mutations in metabolic pathways, including gluconeogenesis and the biosynthesis of lipopolysaccharide (LPS), produced less curli. Regulation of the master biofilm regulator, CsgD, was diverse, and the screen revealed several proteins and small RNAs (sRNA) that regulate csgD messenger RNA (mRNA) levels. Using previously published studies, we found minimal overlap between the genes affecting curli biogenesis and genes known to impact swimming or swarming motility, underlying the distinction between motile and sessile lifestyles. Collectively, the diversity and number of elements required suggest curli production is part of a highly regulated and complex developmental pathway in E. coli.
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Lehning CE, Siedler S, Ellabaan MMH, Sommer MOA. Assessing glycolytic flux alterations resulting from genetic perturbations in E. coli using a biosensor. Metab Eng 2017; 42:194-202. [PMID: 28709932 PMCID: PMC5555440 DOI: 10.1016/j.ymben.2017.07.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Accepted: 07/11/2017] [Indexed: 11/19/2022]
Abstract
We describe the development of an optimized glycolytic flux biosensor and its application in detecting altered flux in a production strain and in a mutant library. The glycolytic flux biosensor is based on the Cra-regulated ppsA promoter of E. coli controlling fluorescent protein synthesis. We validated the glycolytic flux dependency of the biosensor in a range of different carbon sources in six different E. coli strains and during mevalonate production. Furthermore, we studied the flux-altering effects of genome-wide single gene knock-outs in E. coli in a multiplex FlowSeq experiment. From a library consisting of 2126 knock-out mutants, we identified 3 mutants with high-flux and 95 mutants with low-flux phenotypes that did not have severe growth defects. This approach can improve our understanding of glycolytic flux regulation improving metabolic models and engineering efforts.
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Affiliation(s)
- Christina E Lehning
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kemitorvet Building 220, 2800 Lyngby, Denmark
| | - Solvej Siedler
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kemitorvet Building 220, 2800 Lyngby, Denmark
| | - Mostafa M H Ellabaan
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kemitorvet Building 220, 2800 Lyngby, Denmark
| | - Morten O A Sommer
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kemitorvet Building 220, 2800 Lyngby, Denmark.
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28
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Rodionova IA, Zhang Z, Mehla J, Goodacre N, Babu M, Emili A, Uetz P, Saier MH. The phosphocarrier protein HPr of the bacterial phosphotransferase system globally regulates energy metabolism by directly interacting with multiple enzymes in Escherichia coli. J Biol Chem 2017. [PMID: 28634232 DOI: 10.1074/jbc.m117.795294] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The histidine-phosphorylatable phosphocarrier protein (HPr) is an essential component of the sugar-transporting phosphotransferase system (PTS) in many bacteria. Recent interactome findings suggested that HPr interacts with several carbohydrate-metabolizing enzymes, but whether HPr plays a regulatory role was unclear. Here, we provide evidence that HPr interacts with a large number of proteins in Escherichia coli We demonstrate HPr-dependent allosteric regulation of the activities of pyruvate kinase (PykF, but not PykA), phosphofructokinase (PfkB, but not PfkA), glucosamine-6-phosphate deaminase (NagB), and adenylate kinase (Adk). HPr is either phosphorylated on a histidyl residue (HPr-P) or non-phosphorylated (HPr). PykF is activated only by non-phosphorylated HPr, which decreases the PykF Khalf for phosphoenolpyruvate by 10-fold (from 3.5 to 0.36 mm), thus influencing glycolysis. PfkB activation by HPr, but not by HPr-P, resulted from a decrease in the Khalf for fructose-6-P, which likely influences both gluconeogenesis and glycolysis. Moreover, NagB activation by HPr was important for the utilization of amino sugars, and allosteric inhibition of Adk activity by HPr-P, but not by HPr, allows HPr to regulate the cellular energy charge coordinately with glycolysis. These observations suggest that HPr serves as a directly interacting global regulator of carbon and energy metabolism and probably of other physiological processes in enteric bacteria.
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Affiliation(s)
- Irina A Rodionova
- From the Department of Molecular Biology, Division of Biological Sciences, University of California at San Diego, La Jolla, California 92093-0116
| | - Zhongge Zhang
- From the Department of Molecular Biology, Division of Biological Sciences, University of California at San Diego, La Jolla, California 92093-0116
| | - Jitender Mehla
- Center for the Study of Biological Complexity, Virginia Commonwealth University, Richmond, Virginia 23284
| | - Norman Goodacre
- Center for the Study of Biological Complexity, Virginia Commonwealth University, Richmond, Virginia 23284
| | - Mohan Babu
- Department of Biochemistry, Research and Innovation Centre, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
| | - Andrew Emili
- Donnelly Centre, University of Toronto, Toronto, Ontario M5S 3E1, Canada
| | - Peter Uetz
- Center for the Study of Biological Complexity, Virginia Commonwealth University, Richmond, Virginia 23284
| | - Milton H Saier
- From the Department of Molecular Biology, Division of Biological Sciences, University of California at San Diego, La Jolla, California 92093-0116,.
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29
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Wei LN, Zhu LW, Tang YJ. Succinate production positively correlates with the affinity of the global transcription factor Cra for its effector FBP in Escherichia coli. BIOTECHNOLOGY FOR BIOFUELS 2016; 9:264. [PMID: 27980674 PMCID: PMC5146860 DOI: 10.1186/s13068-016-0679-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Accepted: 12/01/2016] [Indexed: 06/06/2023]
Abstract
BACKGROUND Effector binding is important for transcription factors, affecting both the pattern and function of transcriptional regulation to alter cell phenotype. Our previous work suggested that the affinity of the global transcription factor catabolite repressor/activator (Cra) for its effector fructose-1,6-bisphosphate (FBP) may contribute to succinate biosynthesis. To support this hypothesis, single-point and three-point mutations were proposed through the semi-rational design of Cra to improve its affinity for FBP. RESULTS For the first time, a positive correlation between succinate production and the affinity of Cra for FBP was revealed in Escherichia coli. Using the best-fit regression function, a cubic equation was used to examine and describe the relationship between succinate production and the affinity of Cra for FBP, demonstrating a significant positive correlation between the two factors (coefficient of determination R2 = 0.894, P = 0.000 < 0.01). The optimal mutant strain was Tang1683, which provided the lowest mutation energy of -4.78 kcal/mol and the highest succinate concentration of 92.7 g/L, which was 34% higher than that obtained using an empty vector control. The parameters for the interaction between Cra and DNA showed that Cra bound to the promoter regions of pck and aceB to activate the corresponding genes. Normally, Cra-regulated operons under positive control are deactivated in the presence of FBP. Therefore, theoretically, the enhanced affinity of Cra for FBP will inhibit the activation of pck and aceB. However, the activation of genes involved in CO2 fixation and the glyoxylate pathway was further improved by the Cra mutant, ultimately contributing to succinate biosynthesis. CONCLUSIONS Enhanced binding of Cra to FBP or active site mutations may eliminate the repressive effect caused by FBP, thus leading to increased activation of genes associated with succinate biosynthesis in the Cra mutant. This work demonstrates an important transcriptional regulation strategy in the metabolic engineering of succinate production and provides useful information for better understanding of the regulatory mechanisms of transcription factors.
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Affiliation(s)
- Li-Na Wei
- Key Laboratory of Fermentation Engineering (Ministry of Education), Hubei Key Laboratory of Industrial Microbiology, Hubei Provincial Cooperative Innovation Center of Industrial Fermentation, Hubei University of Technology, Wuhan, 430068 China
| | - Li-Wen Zhu
- Key Laboratory of Fermentation Engineering (Ministry of Education), Hubei Key Laboratory of Industrial Microbiology, Hubei Provincial Cooperative Innovation Center of Industrial Fermentation, Hubei University of Technology, Wuhan, 430068 China
| | - Ya-Jie Tang
- Key Laboratory of Fermentation Engineering (Ministry of Education), Hubei Key Laboratory of Industrial Microbiology, Hubei Provincial Cooperative Innovation Center of Industrial Fermentation, Hubei University of Technology, Wuhan, 430068 China
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30
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A Metabolic Widget Adjusts the Phosphoenolpyruvate-Dependent Fructose Influx in Pseudomonas putida. mSystems 2016; 1:mSystems00154-16. [PMID: 27933319 PMCID: PMC5141268 DOI: 10.1128/msystems.00154-16] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Accepted: 11/01/2016] [Indexed: 12/22/2022] Open
Abstract
Fructose uptake in the soil bacterium Pseudomonas putida occurs through a canonical phosphoenolpyruvate (PEP)-dependent sugar transport system (PTSFru). The logic of the genetic circuit that rules its functioning is puzzling: the transcription of the fruBKA operon, encoding all the components of PTSFru, can escape the repression exerted by the catabolite repressor/activator protein Cra solely in the presence of intracellular fructose-1-P, an agonist formed only when fructose has been already transported. To study this apparently incongruous regulatory architecture, the changes in the transcriptome brought about by a seamless Δcra deletion in P. putida strain KT2440 were inspected under different culture conditions. The few genes found to be upregulated in the cra mutant unexpectedly included PP_3443, encoding a bona fide glyceraldehyde-3-P dehydrogenase. An in silico model was developed to explore emergent properties that could result from such connections between sugar uptake with Cra and PEP. Simulation of fructose transport revealed that sugar uptake called for an extra supply of PEP (obtained through the activity of PP_3443) that was kept (i.e., memorized) even when the carbohydrate disappeared from the medium. This feature was traced to the action of two sequential inverters that connect the availability of exogenous fructose to intracellular PEP levels via Cra/PP_3443. The loss of such memory caused a much longer lag phase in cells shifted from one growth condition to another. The term "metabolic widget" is proposed to describe a merged biochemical and regulatory patch that tailors a given node of the cell molecular network to suit species-specific physiological needs. IMPORTANCE The regulatory nodes that govern metabolic traffic in bacteria often show connectivities that could be deemed unnecessarily complex at a first glance. Being a soil dweller and plant colonizer, Pseudomonas putida frequently encounters fructose in the niches that it inhabits. As is the case with many other sugars, fructose is internalized by a dedicated phosphoenolpyruvate (PEP)-dependent transport system (PTSFru), the expression of which is repressed by the fructose-1-P-responding Cra regulatory protein. However, Cra also controls a glyceraldehyde-3-P dehydrogenase that fosters accumulation of PEP (i.e., the metabolic fuel for PTSFru). A simple model representing this metabolic and regulatory device revealed that such an unexpected connectivity allows cells to shift smoothly between fructose-rich and fructose-poor conditions. Therefore, although the metabolic networks that handle sugar (i.e., fructose) consumption look very similar in most eubacteria, the way in which their components are intertwined endows given microorganisms with emergent properties for meeting species-specific and niche-specific needs.
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31
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Zhu LW, Xia ST, Wei LN, Li HM, Yuan ZP, Tang YJ. Enhancing succinic acid biosynthesis in Escherichia coli by engineering its global transcription factor, catabolite repressor/activator (Cra). Sci Rep 2016; 6:36526. [PMID: 27811970 PMCID: PMC5109907 DOI: 10.1038/srep36526] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2016] [Accepted: 10/17/2016] [Indexed: 11/09/2022] Open
Abstract
This study was initiated to improve E. coli succinate production by engineering the E. coli global transcription factor, Cra (catabolite repressor/activator). Random mutagenesis libraries were generated through error-prone PCR of cra. After re-screening and mutation site integration, the best mutant strain was Tang1541, which provided a final succinate concentration of 79.8 ± 3.1 g/L: i.e., 22.8% greater than that obtained using an empty vector control. The genes and enzymes involved in phosphoenolpyruvate (PEP) carboxylation and the glyoxylate pathway were activated, either directly or indirectly, through the mutation of Cra. The parameters for interaction of Cra and DNA indicated that the Cra mutant was bound to aceBAK, thereby activating the genes involved in glyoxylate pathway and further improving succinate production even in the presence of its effector fructose-1,6-bisphosphate (FBP). It suggested that some of the negative effect of FBP on Cra might have been counteracted through the enhanced binding affinity of the Cra mutant for FBP or the change of Cra structure. This work provides useful information about understanding the transcriptional regulation of succinate biosynthesis.
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Affiliation(s)
- Li-Wen Zhu
- School of Public Health, Wuhan University, Wuhan 430071 China.,Key Laboratory of Fermentation Engineering (Ministry of Education), Hubei Key Laboratory of Industrial Microbiology, Hubei Provincial Cooperative Innovation Center of Industrial Fermentation, Hubei University of Technology, Wuhan 430068 China
| | - Shi-Tao Xia
- Key Laboratory of Fermentation Engineering (Ministry of Education), Hubei Key Laboratory of Industrial Microbiology, Hubei Provincial Cooperative Innovation Center of Industrial Fermentation, Hubei University of Technology, Wuhan 430068 China
| | - Li-Na Wei
- Key Laboratory of Fermentation Engineering (Ministry of Education), Hubei Key Laboratory of Industrial Microbiology, Hubei Provincial Cooperative Innovation Center of Industrial Fermentation, Hubei University of Technology, Wuhan 430068 China
| | - Hong-Mei Li
- Key Laboratory of Fermentation Engineering (Ministry of Education), Hubei Key Laboratory of Industrial Microbiology, Hubei Provincial Cooperative Innovation Center of Industrial Fermentation, Hubei University of Technology, Wuhan 430068 China
| | - Zhan-Peng Yuan
- School of Public Health, Wuhan University, Wuhan 430071 China
| | - Ya-Jie Tang
- Key Laboratory of Fermentation Engineering (Ministry of Education), Hubei Key Laboratory of Industrial Microbiology, Hubei Provincial Cooperative Innovation Center of Industrial Fermentation, Hubei University of Technology, Wuhan 430068 China
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32
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Modulating the direction of carbon flow in Escherichia coli to improve l-tryptophan production by inactivating the global regulator FruR. J Biotechnol 2016; 231:141-148. [PMID: 27297546 DOI: 10.1016/j.jbiotec.2016.06.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Revised: 05/30/2016] [Accepted: 06/09/2016] [Indexed: 11/22/2022]
Abstract
The fructose repressor (FruR) affects carbon flux through the central metabolic pathways of Escherichia coli. In this study, l-tryptophan production in Escherichia coli FB-04 was improved by knocking out the fruR gene, thereby inactivating FruR. This fruR knockout strain, E. coli FB-04(ΔfruR), not only exhibited higher growth efficiency, it also showed substantially improved l-tryptophan production. l-tryptophan production by E. coli FB-04(ΔfruR) and l-tryptophan yield per glucose were increased by 62.5% and 52.4%, respectively, compared with the parent E. coli FB-04. Metabolomics analysis showed that the fruR knockout significantly enhances metabolic flow through glycolysis, the pentose phosphate pathway and the TCA cycle, increasing levels of critical precursors and substrates for l-tryptophan biosynthesis. These results indicate that fruR deletion should enhance l-tryptophan production and improve the efficiency of carbon source utilization independent of genetic background.
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33
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The RNA-Binding Chaperone Hfq Is an Important Global Regulator of Gene Expression in Pasteurella multocida and Plays a Crucial Role in Production of a Number of Virulence Factors, Including Hyaluronic Acid Capsule. Infect Immun 2016; 84:1361-1370. [PMID: 26883595 DOI: 10.1128/iai.00122-16] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 02/11/2016] [Indexed: 12/19/2022] Open
Abstract
The Gram-negative bacterium Pasteurella multocida is the causative agent of a number of economically important animal diseases, including avian fowl cholera. Numerous P. multocida virulence factors have been identified, including capsule, lipopolysaccharide (LPS), and filamentous hemagglutinin, but little is known about how the expression of these virulence factors is regulated. Hfq is an RNA-binding protein that facilitates riboregulation via interaction with small noncoding RNA (sRNA) molecules and their mRNA targets. Here, we show that a P. multocida hfq mutant produces significantly less hyaluronic acid capsule during all growth phases and displays reduced in vivo fitness. Transcriptional and proteomic analyses of the hfq mutant during mid-exponential-phase growth revealed altered transcript levels for 128 genes and altered protein levels for 78 proteins. Further proteomic analyses of the hfq mutant during the early exponential growth phase identified 106 proteins that were produced at altered levels. Both the transcript and protein levels for genes/proteins involved in capsule biosynthesis were reduced in the hfq mutant, as were the levels of the filamentous hemagglutinin protein PfhB2 and its secretion partner LspB2. In contrast, there were increased expression levels of three LPS biosynthesis genes, encoding proteins involved in phosphocholine and phosphoethanolamine addition to LPS, suggesting that these genes are negatively regulated by Hfq-dependent mechanisms. Taken together, these data provide the first evidence that Hfq plays a crucial role in regulating the global expression of P. multocida genes, including the regulation of key P. multocida virulence factors, capsule, LPS, and filamentous hemagglutinin.
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34
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Reshamwala SMS, Mamidipally C, Pissurlenkar RRS, Coutinho EC, Noronha SB. Evaluation of risedronate as an antibiofilm agent. J Med Microbiol 2016; 65:9-18. [DOI: 10.1099/jmm.0.000193] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Shamlan M. S. Reshamwala
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India
| | | | - Raghuvir R. S. Pissurlenkar
- Molecular Simulations Group, Department of Pharmaceutical Chemistry, Goa College of Pharmacy, , Panaji, India
| | - Evans C. Coutinho
- Department of Pharmaceutical Chemistry, Bombay College of Pharmacy, , Mumbai, India
| | - Santosh B. Noronha
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, India
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35
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Cameron EA, Sperandio V. Frenemies: Signaling and Nutritional Integration in Pathogen-Microbiota-Host Interactions. Cell Host Microbe 2015; 18:275-84. [PMID: 26355214 PMCID: PMC4567707 DOI: 10.1016/j.chom.2015.08.007] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The mammalian gastrointestinal (GI) microbiota is highly adapted to thrive in the GI environment and performs key functions related to host nutrition, physiology, development, immunity, and behavior. Successful host-bacterial associations require chemical signaling and optimal nutrient utilization and exchange. However, this important balance can be severely disrupted by environmental stimuli, with one of the most common insults upon the microbiota being infectious diseases. Although the microbiota acts as a barrier toward enteric pathogens, many enteric pathogens exploit signals and nutrients derived from both the microbiota and host to regulate their virulence programs. Here we review several signaling and nutrient recognition systems employed by GI pathogens to regulate growth and virulence. We discuss how shifts in the microbiota composition change host susceptibility to infection and how dietary changes or manipulation of the microbiota could potentially prevent and/or ameliorate GI infections.
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Affiliation(s)
- Elizabeth A Cameron
- Departments of Microbiology and Biochemistry, UT Southwestern Medical Center, Dallas, TX 75390-9048, USA
| | - Vanessa Sperandio
- Departments of Microbiology and Biochemistry, UT Southwestern Medical Center, Dallas, TX 75390-9048, USA.
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Imam S, Schäuble S, Brooks AN, Baliga NS, Price ND. Data-driven integration of genome-scale regulatory and metabolic network models. Front Microbiol 2015; 6:409. [PMID: 25999934 PMCID: PMC4419725 DOI: 10.3389/fmicb.2015.00409] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2015] [Accepted: 04/20/2015] [Indexed: 12/21/2022] Open
Abstract
Microbes are diverse and extremely versatile organisms that play vital roles in all ecological niches. Understanding and harnessing microbial systems will be key to the sustainability of our planet. One approach to improving our knowledge of microbial processes is through data-driven and mechanism-informed computational modeling. Individual models of biological networks (such as metabolism, transcription, and signaling) have played pivotal roles in driving microbial research through the years. These networks, however, are highly interconnected and function in concert-a fact that has led to the development of a variety of approaches aimed at simulating the integrated functions of two or more network types. Though the task of integrating these different models is fraught with new challenges, the large amounts of high-throughput data sets being generated, and algorithms being developed, means that the time is at hand for concerted efforts to build integrated regulatory-metabolic networks in a data-driven fashion. In this perspective, we review current approaches for constructing integrated regulatory-metabolic models and outline new strategies for future development of these network models for any microbial system.
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Affiliation(s)
- Saheed Imam
- Institute for Systems Biology Seattle, WA, USA
| | - Sascha Schäuble
- Institute for Systems Biology Seattle, WA, USA ; Jena University Language and Information Engineering Lab, Friedrich-Schiller-University Jena Jena, Germany
| | | | - Nitin S Baliga
- Institute for Systems Biology Seattle, WA, USA ; Departments of Biology and Microbiology, University of Washington Seattle, WA, USA ; Molecular and Cellular Biology Program, University of Washington Seattle, WA, USA ; Lawrence Berkeley National Lab Berkeley, CA, USA
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Abstract
UNLABELLED Many pathways of carbon and energy metabolism are conserved across the phylogeny, but the networks that regulate their expression or activity often vary considerably among organisms. In this work, we show that two previously uncharacterized transcription factors (TFs) are direct regulators of genes encoding enzymes of central carbon and energy metabolism in the alphaproteobacterium Rhodobacter sphaeroides. The LacI family member CceR (RSP_1663) directly represses genes encoding enzymes in the Entner-Doudoroff pathway, while activating those encoding the F1F0 ATPase and enzymes of the tricarboxylic acid (TCA) cycle and gluconeogenesis, providing a direct transcriptional network connection between carbon and energy metabolism. We identified bases that are important for CceR DNA binding and showed that DNA binding by this TF is inhibited by 6-phosphogluconate. We also showed that the GntR family TF AkgR (RSP_0981) directly activates genes encoding several TCA cycle enzymes, and we identified conditions where its activity is increased. The properties of single and double ΔCceR and ΔAkgR mutants illustrate that these 2 TFs cooperatively regulate carbon and energy metabolism. Comparative genomic analysis indicates that CceR and AkgR orthologs are found in other alphaproteobacteria, where they are predicted to have a conserved function in regulating central carbon metabolism. Our characterization of CceR and AkgR has provided important new insight into the networks that control central carbon and energy metabolism in alphaproteobacteria that can be exploited to modify or engineer new traits in these widespread and versatile bacteria. IMPORTANCE To extract and conserve energy from nutrients, cells coordinate a set of metabolic pathways into integrated networks. Many pathways that conserve energy or interconvert metabolites are conserved across cells, but the networks regulating these processes are often highly variable. In this study, we characterize two previously unknown transcriptional regulators of carbon and energy metabolism that are conserved in alphaproteobacteria, a group of abundant, environmentally and biotechnologically important organisms. We identify the genes they regulate, the DNA sequences they recognize, the metabolite that controls the activity of one of the regulators, and conditions where they are required for growth. We provide important new insight into conserved cellular networks that can also be used to improve a variety of hosts for converting feedstock into valuable products.
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Jung MY, Jung HM, Lee J, Oh MK. Alleviation of carbon catabolite repression in Enterobacter aerogenes for efficient utilization of sugarcane molasses for 2,3-butanediol production. BIOTECHNOLOGY FOR BIOFUELS 2015; 8:106. [PMID: 26236395 PMCID: PMC4521459 DOI: 10.1186/s13068-015-0290-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Accepted: 07/22/2015] [Indexed: 05/23/2023]
Abstract
BACKGROUND Due to its cost-effectiveness and rich sugar composition, sugarcane molasses is considered to be a promising carbon source for biorefinery. However, the sugar mixture in sugarcane molasses is not consumed as efficiently as glucose in microbial fermentation due to complex interactions among their utilizing pathways, such as carbon catabolite repression (CCR). In this study, 2,3-butanediol-producing Enterobacter aerogenes was engineered to alleviate CCR and improve sugar utilization by modulating its carbon preference. RESULTS The gene encoding catabolite repressor/activator (Cra) was deleted in the genome of E. aerogenes to increase the fructose consumption rate. However, the deletion mutation repressed sucrose utilization, resulting in the accumulation of sucrose in the fermentation medium. Cra regulation on expression of the scrAB operon involved in sucrose catabolism was verified by reverse transcription and real-time PCR, and the efficiency of sucrose utilization was restored by disrupting the scrR gene and overexpressing the scrAB operon. In addition, overexpression of the ptsG gene involved in glucose utilization enhanced the glucose preference among mixed sugars, which relieved glucose accumulation in fed-batch fermentation. In fed-batch fermentation using sugarcane molasses, the maximum titer of 2,3-butanediol production by the mutant reached 140.0 g/L at 54 h, which was by far the highest titer of 2,3-butanediol with E. aerogenes achieved through genetic engineering. CONCLUSIONS We have developed genetically engineered E. aerogenes as a 2,3-butanediol producer that efficiently utilizes sugarcane molasses. The fermentation efficiency was dramatically improved by the alleviation of CCR and modulation of carbon preference. These results offer a metabolic engineering approach for achieving highly efficient utilization of mixed sugars for the biorefinery industry.
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Affiliation(s)
- Moo-Young Jung
- />Department of Chemical and Biological Engineering, Korea University, Seoul, Republic of Korea
| | - Hwi-Min Jung
- />Department of Chemical and Biological Engineering, Korea University, Seoul, Republic of Korea
| | - Jinwon Lee
- />Department of Chemical and Biomolecular Engineering, Sogang University, Seoul, Republic of Korea
| | - Min-Kyu Oh
- />Department of Chemical and Biological Engineering, Korea University, Seoul, Republic of Korea
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Zhang Z, Aboulwafa M, Saier MH. Regulation of crp gene expression by the catabolite repressor/activator, Cra, in Escherichia coli. J Mol Microbiol Biotechnol 2014; 24:135-41. [PMID: 24923415 DOI: 10.1159/000362722] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Growth of E. coli on several carbon sources is dependent on the catabolite repressor/activator (Cra) protein although a Cra consensus DNA-binding site is not present in the control regions of the relevant catabolic operons. We show that Cra regulates growth by activating expression of the crp gene. It thereby mediates catabolite repression of catabolic operons by an indirect mechanism.
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Affiliation(s)
- Zhongge Zhang
- Department of Molecular Biology, Division of Biological Sciences, University of California at San Diego, La Jolla, Calif., USA
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Chavarría M, Durante-Rodríguez G, Krell T, Santiago C, Brezovsky J, Damborsky J, de Lorenzo V. Fructose 1-phosphate is the one and only physiological effector of the Cra (FruR) regulator of Pseudomonas putida. FEBS Open Bio 2014; 4:377-86. [PMID: 24918052 PMCID: PMC4050194 DOI: 10.1016/j.fob.2014.03.013] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Revised: 03/31/2014] [Accepted: 03/31/2014] [Indexed: 11/11/2022] Open
Abstract
The role of FBP as effector of the Cra protein of soil bacterium Pseudomonas putida is unclear. Biochemical, biophysical and genetic data show that Cra binds only F1P as metabolic agonist. F1P is the only physiological effector of the Cra protein of P. putida in vivo. This regulatory exaptation of Cra exemplifies how transcriptional factors can diversify in bacteria.
Fructose-1-phosphate (F1P) is the preferred effector of the catabolite repressor/activator (Cra) protein of the soil bacterium Pseudomonas putida but its ability to bind other metabolic intermediates in vivo is unclear. The Cra protein of this microorganism (CraPP) was submitted to mobility shift assays with target DNA sequences (the PfruB promoter) and candidate effectors fructose-1,6-bisphosphate (FBP), glucose 6-phosphate (G6P), and fructose-6-phosphate (F6P). 1 mM F1P was sufficient to release most of the Cra protein from its operators but more than 10 mM of FBP or G6P was required to free the same complex. However, isothermal titration microcalorimetry failed to expose any specific interaction between CraPP and FBP or G6P. To solve this paradox, transcriptional activity of a PfruB-lacZ fusion was measured in wild-type and ΔfruB cells growing on substrates that change the intracellular concentrations of F1P and FBP. The data indicated that PfruB activity was stimulated by fructose but not by glucose or succinate. This suggested that CraPP represses expression in vivo of the cognate fruBKA operon in a fashion dependent just on F1P, ruling out any other physiological effector. Molecular docking and dynamic simulations of the Cra-agonist interaction indicated that both metabolites can bind the repressor, but the breach in the relative affinity of CraPP for F1P vs FBP is three orders of magnitude larger than the equivalent distance in the Escherichia coli protein. This assigns the Cra protein of P. putida the sole role of transducing the presence of fructose in the medium into a variety of direct and indirect physiological responses.
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Affiliation(s)
- Max Chavarría
- Systems and Synthetic Biology Program, Centro Nacional de Biotecnología (CNB-CSIC), Cantoblanco, Madrid 28049, Spain ; Escuela de Química, Universidad de Costa Rica, 2060 San José, Costa Rica
| | - Gonzalo Durante-Rodríguez
- Systems and Synthetic Biology Program, Centro Nacional de Biotecnología (CNB-CSIC), Cantoblanco, Madrid 28049, Spain
| | - Tino Krell
- Department of Environmental Protection, Estación Experimental del Zaidín, CSIC, C/Profesor Albareda, Granada, Spain
| | - César Santiago
- X-ray Crystallography Unit, Centro Nacional de Biotecnología (CNB-CSIC), Cantoblanco, Madrid 28049, Spain
| | - Jan Brezovsky
- Loschmidt Laboratories, Department of Experimental Biology and Research Centre for Toxic Compounds in the Environment (RECETOX), Faculty of Science, Masaryk University, Kamenice 5/A13, 625 00 Brno, Czech Republic
| | - Jiri Damborsky
- Loschmidt Laboratories, Department of Experimental Biology and Research Centre for Toxic Compounds in the Environment (RECETOX), Faculty of Science, Masaryk University, Kamenice 5/A13, 625 00 Brno, Czech Republic
| | - Víctor de Lorenzo
- Systems and Synthetic Biology Program, Centro Nacional de Biotecnología (CNB-CSIC), Cantoblanco, Madrid 28049, Spain
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k-OptForce: integrating kinetics with flux balance analysis for strain design. PLoS Comput Biol 2014; 10:e1003487. [PMID: 24586136 PMCID: PMC3930495 DOI: 10.1371/journal.pcbi.1003487] [Citation(s) in RCA: 104] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Accepted: 01/10/2014] [Indexed: 11/19/2022] Open
Abstract
Computational strain design protocols aim at the system-wide identification of intervention strategies for the enhanced production of biochemicals in microorganisms. Existing approaches relying solely on stoichiometry and rudimentary constraint-based regulation overlook the effects of metabolite concentrations and substrate-level enzyme regulation while identifying metabolic interventions. In this paper, we introduce k-OptForce, which integrates the available kinetic descriptions of metabolic steps with stoichiometric models to sharpen the prediction of intervention strategies for improving the bio-production of a chemical of interest. It enables identification of a minimal set of interventions comprised of both enzymatic parameter changes (for reactions with available kinetics) and reaction flux changes (for reactions with only stoichiometric information). Application of k-OptForce to the overproduction of L-serine in E. coli and triacetic acid lactone (TAL) in S. cerevisiae revealed that the identified interventions tend to cause less dramatic rearrangements of the flux distribution so as not to violate concentration bounds. In some cases the incorporation of kinetic information leads to the need for additional interventions as kinetic expressions render stoichiometry-only derived interventions infeasible by violating concentration bounds, whereas in other cases the kinetic expressions impart flux changes that favor the overproduction of the target product thereby requiring fewer direct interventions. A sensitivity analysis on metabolite concentrations shows that the required number of interventions can be significantly affected by changing the imposed bounds on metabolite concentrations. Furthermore, k-OptForce was capable of finding non-intuitive interventions aiming at alleviating the substrate-level inhibition of key enzymes in order to enhance the flux towards the product of interest, which cannot be captured by stoichiometry-alone analysis. This study paves the way for the integrated analysis of kinetic and stoichiometric models and enables elucidating system-wide metabolic interventions while capturing regulatory and kinetic effects.
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Pieper R, Zhang Q, Clark DJ, Parmar PP, Alami H, Suh MJ, Kuntumalla S, Braisted JC, Huang ST, Tzipori S. Proteomic View of Interactions of Shiga Toxin-Producing Escherichia coli with the Intestinal Environment in Gnotobiotic Piglets. PLoS One 2013; 8:e66462. [PMID: 23840478 PMCID: PMC3686733 DOI: 10.1371/journal.pone.0066462] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Accepted: 05/05/2013] [Indexed: 01/21/2023] Open
Abstract
BACKGROUND Shiga toxin (Stx)-producing Escherichia coli cause severe intestinal infections involving colonization of epithelial Peyer's patches and formation of attachment/effacement (A/E) lesions. These lesions trigger leukocyte infiltration followed by inflammation and intestinal hemorrhage. Systems biology, which explores the crosstalk of Stx-producing Escherichia coli with the in vivo host environment, may elucidate novel molecular pathogenesis aspects. METHODOLOGY/PRINCIPAL FINDINGS Enterohemorrhagic E. coli strain 86-24 produces Shiga toxin-2 and belongs to the serotype O157:H7. Bacterial cells were scrapped from stationary phase cultures (the in vitro condition) and used to infect gnotobiotic piglets via intestinal lavage. Bacterial cells isolated from the piglets' guts constituted the in vivo condition. Cell lysates were subjected to quantitative 2D gel and shotgun proteomic analyses, revealing metabolic shifts towards anaerobic energy generation, changes in carbon utilization, phosphate and ammonia starvation, and high activity of a glutamate decarboxylase acid resistance system in vivo. Increased abundance of pyridine nucleotide transhydrogenase (PntA and PntB) suggested in vivo shortage of intracellular NADPH. Abundance changes of proteins implicated in lipopolysaccharide biosynthesis (LpxC, ArnA, the predicted acyltransferase L7029) and outer membrane (OM) assembly (LptD, MlaA, MlaC) suggested bacterial cell surface modulation in response to activated host defenses. Indeed, there was evidence for interactions of innate immunity-associated proteins secreted into the intestines (GP340, REG3-γ, resistin, lithostathine, and trefoil factor 3) with the bacterial cell envelope. SIGNIFICANCE Proteomic analysis afforded insights into system-wide adaptations of strain 86-24 to a hostile intestinal milieu, including responses to limited nutrients and cofactor supplies, intracellular acidification, and reactive nitrogen and oxygen species-mediated stress. Protein and lipopolysaccharide compositions of the OM were altered. Enhanced expression of type III secretion system effectors correlated with a metabolic shift back to a more aerobic milieu in vivo. Apparent pathogen pattern recognition molecules from piglet intestinal secretions adhered strongly to the bacterial cell surface.
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Affiliation(s)
- Rembert Pieper
- J. Craig Venter Institute, Rockville, Maryland, United States of America
- * E-mail:
| | - Quanshun Zhang
- Division of Infectious Diseases, Cummings School of Veterinary Medicine, Tufts University, North Grafton, Massachusetts, United States of America
| | - David J. Clark
- J. Craig Venter Institute, Rockville, Maryland, United States of America
| | | | - Hamid Alami
- J. Craig Venter Institute, Rockville, Maryland, United States of America
| | - Moo-Jin Suh
- J. Craig Venter Institute, Rockville, Maryland, United States of America
| | | | - John C. Braisted
- J. Craig Venter Institute, Rockville, Maryland, United States of America
| | - Shih-Ting Huang
- J. Craig Venter Institute, Rockville, Maryland, United States of America
| | - Saul Tzipori
- Division of Infectious Diseases, Cummings School of Veterinary Medicine, Tufts University, North Grafton, Massachusetts, United States of America
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Wang H, Liu B, Wang Q, Wang L. Genome-wide analysis of the salmonella Fis regulon and its regulatory mechanism on pathogenicity islands. PLoS One 2013; 8:e64688. [PMID: 23717649 PMCID: PMC3662779 DOI: 10.1371/journal.pone.0064688] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Accepted: 04/17/2013] [Indexed: 11/19/2022] Open
Abstract
Fis, one of the most important nucleoid-associated proteins, functions as a global regulator of transcription in bacteria that has been comprehensively studied in Escherichia coli K12. Fis also influences the virulence of Salmonella enterica and pathogenic E. coli by regulating their virulence genes, however, the relevant mechanism is unclear. In this report, using combined RNA-seq and chromatin immunoprecipitation (ChIP)-seq technologies, we first identified 1646 Fis-regulated genes and 885 Fis-binding targets in the S. enterica serovar Typhimurium, and found a Fis regulon different from that in E. coli. Fis has been reported to contribute to the invasion ability of S. enterica. By using cell infection assays, we found it also enhances the intracellular replication ability of S. enterica within macrophage cell, which is of central importance for the pathogenesis of infections. Salmonella pathogenicity islands (SPI)-1 and SPI-2 are crucial for the invasion and survival of S. enterica in host cells. Using mutation and overexpression experiments, real-time PCR analysis, and electrophoretic mobility shift assays, we demonstrated that Fis regulates 63 of the 94 Salmonella pathogenicity island (SPI)-1 and SPI-2 genes, by three regulatory modes: i) binds to SPI regulators in the gene body or in upstream regions; ii) binds to SPI genes directly to mediate transcriptional activation of themselves and downstream genes; iii) binds to gene encoding OmpR which affects SPI gene expression by controlling SPI regulators SsrA and HilD. Our results provide new insights into the impact of Fis on SPI genes and the pathogenicity of S. enterica.
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Affiliation(s)
- Hui Wang
- TEDA School of Biological Sciences and Biotechnology, Nankai University, TEDA, Tianjin, P. R. China
- Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin, P. R. China
| | - Bin Liu
- TEDA School of Biological Sciences and Biotechnology, Nankai University, TEDA, Tianjin, P. R. China
- Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin, P. R. China
| | - Quan Wang
- TEDA School of Biological Sciences and Biotechnology, Nankai University, TEDA, Tianjin, P. R. China
- Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin, P. R. China
| | - Lei Wang
- TEDA School of Biological Sciences and Biotechnology, Nankai University, TEDA, Tianjin, P. R. China
- Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin, P. R. China
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin, P. R. China
- * E-mail:
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Dissecting specific and global transcriptional regulation of bacterial gene expression. Mol Syst Biol 2013; 9:658. [PMID: 23591774 PMCID: PMC3658269 DOI: 10.1038/msb.2013.14] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Accepted: 03/06/2013] [Indexed: 12/18/2022] Open
Abstract
Gene expression is regulated by specific transcriptional circuits but also by the global expression machinery as a function of growth. Simultaneous specific and global regulation thus constitutes an additional--but often neglected--layer of complexity in gene expression. Here, we develop an experimental-computational approach to dissect specific and global regulation in the bacterium Escherichia coli. By using fluorescent promoter reporters, we show that global regulation is growth rate dependent not only during steady state but also during dynamic changes in growth rate and can be quantified through two promoter-specific parameters. By applying our approach to arginine biosynthesis, we obtain a quantitative understanding of both specific and global regulation that allows accurate prediction of the temporal response to simultaneous perturbations in arginine availability and growth rate. We thereby uncover two principles of joint regulation: (i) specific regulation by repression dominates the transcriptional response during metabolic steady states, largely repressing the biosynthesis genes even when biosynthesis is required and (ii) global regulation sets the maximum promoter activity that is exploited during the transition between steady states.
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The interacting Cra and KdpE regulators are involved in the expression of multiple virulence factors in enterohemorrhagic Escherichia coli. J Bacteriol 2013; 195:2499-508. [PMID: 23524613 DOI: 10.1128/jb.02252-12] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The human pathogen enterohemorrhagic Escherichia coli (EHEC) O157:H7 codes for two interacting DNA binding proteins, Cra and KdpE, that coregulate expression of the locus of enterocyte effacement (LEE) genes in a metabolite-dependent manner. Cra is a transcription factor that uses fluctuations in the concentration of carbon metabolism intermediates to positively regulate virulence of EHEC. KdpE is a response regulator that activates the transcription of homeostasis genes in response to salt-induced osmolarity and virulence genes in response to changes in metabolite concentrations. Here, we probed the transcriptional profiles of the Δcra, ΔkdpE, and Δcra ΔkdpE mutant strains and show that Cra and KdpE share several targets besides the LEE, but both Cra and KdpE also have independent targets. Several genes within O-islands (genomic islands present in EHEC but absent from E. coli K-12), such as Z0639, Z0640, Z3388, Z4267, and espFu (encoding an effector necessary for formation of attaching and effacing lesions on epithelial cells), were directly regulated by both Cra and KdpE, while Z2077 was only regulated by Cra. These studies identified and confirmed new direct targets for Cra and KdpE that included putative virulence factors as well as characterized virulence factors, such as EspFu and EspG. These results map out the role of the two interacting regulators, Cra and KdpE, in EHEC pathogenesis and global gene regulation.
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Shimizu K. Metabolic Regulation of a Bacterial Cell System with Emphasis on Escherichia coli Metabolism. ISRN BIOCHEMISTRY 2013; 2013:645983. [PMID: 25937963 PMCID: PMC4393010 DOI: 10.1155/2013/645983] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Accepted: 10/25/2012] [Indexed: 12/19/2022]
Abstract
It is quite important to understand the overall metabolic regulation mechanism of bacterial cells such as Escherichia coli from both science (such as biochemistry) and engineering (such as metabolic engineering) points of view. Here, an attempt was made to clarify the overall metabolic regulation mechanism by focusing on the roles of global regulators which detect the culture or growth condition and manipulate a set of metabolic pathways by modulating the related gene expressions. For this, it was considered how the cell responds to a variety of culture environments such as carbon (catabolite regulation), nitrogen, and phosphate limitations, as well as the effects of oxygen level, pH (acid shock), temperature (heat shock), and nutrient starvation.
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Affiliation(s)
- Kazuyuki Shimizu
- Kyushu Institute of Technology, Fukuoka, Iizuka 820-8502, Japan
- Institute of Advanced Bioscience, Keio University, Yamagata, Tsuruoka 997-0017, Japan
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Kremling A, Goehler A, Jahreis K, Nees M, Auerbach B, Schmidt-Heck W, Kökpinar O, Geffers R, Rinas U, Bettenbrock K. Analysis and Design of Stimulus Response Curves of E. coli. Metabolites 2012; 2:844-71. [PMID: 24957765 PMCID: PMC3901224 DOI: 10.3390/metabo2040844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Accepted: 10/29/2012] [Indexed: 11/16/2022] Open
Abstract
Metabolism and signalling are tightly coupled in bacteria. Combining several theoretical approaches, a core model is presented that describes transcriptional and allosteric control of glycolysis in Escherichia coli. Experimental data based on microarrays, signaling components and extracellular metabolites are used to estimate kinetic parameters. A newly designed strain was used that adjusts the incoming glucose flux into the system and allows a kinetic analysis. Based on the results, prediction for intracelluar metabolite concentrations over a broad range of the growth rate could be performed and compared with data from literature.
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Affiliation(s)
- Andreas Kremling
- Systems Biotechnology, Technische Universität München, Boltzmannstr. 15, Garching b. München, Germany.
| | - Anna Goehler
- University Osnabrück, Barbarastrasse 11, Osnabrück, Germany.
| | - Knut Jahreis
- University Osnabrück, Barbarastrasse 11, Osnabrück, Germany.
| | - Markus Nees
- Max Planck Institute for Dynamics of Complex Technical Systems, Magdeburg, Germany.
| | - Benedikt Auerbach
- Systems Biotechnology, Technische Universität München, Boltzmannstr. 15, Garching b. München, Germany.
| | | | - Oznur Kökpinar
- Helmholtz Center for Infection Research, Inhoffenstr. 7, Braunschweig, Germany.
| | - Robert Geffers
- Helmholtz Center for Infection Research, Inhoffenstr. 7, Braunschweig, Germany.
| | - Ursula Rinas
- Helmholtz Center for Infection Research, Inhoffenstr. 7, Braunschweig, Germany.
| | - Katja Bettenbrock
- Max Planck Institute for Dynamics of Complex Technical Systems, Magdeburg, Germany.
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Molecular control of sucrose utilization in Escherichia coli W, an efficient sucrose-utilizing strain. Appl Environ Microbiol 2012; 79:478-87. [PMID: 23124236 DOI: 10.1128/aem.02544-12] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sucrose is an industrially important carbon source for microbial fermentation. Sucrose utilization in Escherichia coli, however, is poorly understood, and most industrial strains cannot utilize sucrose. The roles of the chromosomally encoded sucrose catabolism (csc) genes in E. coli W were examined by knockout and overexpression experiments. At low sucrose concentrations, the csc genes are repressed and cells cannot grow. Removal of either the repressor protein (cscR) or the fructokinase (cscK) gene facilitated derepression. Furthermore, combinatorial knockout of cscR and cscK conferred an improved growth rate on low sucrose. The invertase (cscA) and sucrose transporter (cscB) genes are essential for sucrose catabolism in E. coli W, demonstrating that no other genes can provide sucrose transport or inversion activities. However, cscK is not essential for sucrose utilization. Fructose is excreted into the medium by the cscK-knockout strain in the presence of high sucrose, whereas at low sucrose (when carbon availability is limiting), fructose is utilized by the cell. Overexpression of cscA, cscAK, or cscAB could complement the WΔcscRKAB knockout mutant or confer growth on a K-12 strain which could not naturally utilize sucrose. However, phenotypic stability and relatively good growth rates were observed in the K-12 strain only when overexpressing cscAB, and full growth rate complementation in WΔcscRKAB also required cscAB. Our understanding of sucrose utilization can be used to improve E. coli W and engineer sucrose utilization in strains which do not naturally utilize sucrose, allowing substitution of sucrose for other, less desirable carbon sources in industrial fermentations.
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Abstract
Gastrointestinal (GI) bacteria sense diverse environmental signals as cues for differential gene regulation and niche adaptation. Pathogens such as enterohemorrhagic Escherichia coli (EHEC), which causes bloody diarrhea, use these signals for the temporal and energy-efficient regulation of their virulence factors. One of the main virulence strategies employed by EHEC is the formation of attaching and effacing (AE) lesions on enterocytes. Most of the genes necessary for the formation of these lesions are grouped within a pathogenicity island, the locus of enterocyte effacement (LEE), whose expression requires the LEE-encoded regulator Ler. Here we show that growth of EHEC in glycolytic environments inhibits the expression of ler and consequently all other LEE genes. Conversely, growth within a gluconeogenic environment activates expression of these genes. This sugar-dependent regulation is achieved through two transcription factors: KdpE and Cra. Both Cra and KdpE directly bind to the ler promoter, and Cra’s affinity to this promoter is catabolite dependent. Moreover, we show that the Cra and KdpE proteins interact in vitro and that KdpE’s ability to bind DNA is enhanced by the presence of Cra. Cra is important for AE lesion formation, and KdpE contributes to this Cra-dependent regulation. The deletion of cra and kdpE resulted in the ablation of AE lesions. One of the many challenges that bacteria face within the GI tract is to successfully compete for carbon sources. Linking carbon metabolism to the precise coordination of virulence expression is a key step in the adaptation of pathogens to the GI environment. An appropriate and prompt response to environmental cues is crucial for bacterial survival. Cra and KdpE are two proteins found in both nonpathogenic and pathogenic bacteria that regulate genes in response to differences in metabolite concentration. In this work, we show that, in the deadly pathogen enterohemorrhagic Escherichia coli (EHEC) O157:H7, which causes bloody diarrhea, these two proteins influence important virulence traits. We also propose that their control of one or more of these virulence traits is due to the direct interaction of the Cra and KdpE proteins with each other, as well as with their DNA targets. This work shows how EHEC coopts established mechanisms for sensing the metabolites and stress cues in the environment, to induce virulence factors in a temporal and energy-efficient manner, culminating in disease. Understanding how pathogens commandeer nonpathogenic systems can help us develop measures to control them.
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Chavarría M, Fuhrer T, Sauer U, Pflüger-Grau K, de Lorenzo V. Cra regulates the cross-talk between the two branches of the phosphoenolpyruvate : phosphotransferase system of Pseudomonas putida. Environ Microbiol 2012; 15:121-32. [PMID: 22708906 DOI: 10.1111/j.1462-2920.2012.02808.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The gene that encodes the catabolite repressor/activator, Cra (FruR), of Pseudomonas putida is divergent from the fruBKA operon for the uptake of fructose via the phosphoenolpyruvate : carbohydrate phosphotransferase system (PTS(Fru)). The expression of the fru cluster has been studied in cells growing on substrates that change the intracellular concentrations of fructose-1-P (F1P), the principal metabolic intermediate that counteracts the DNA-binding ability of Cra on an upstream operator. While the levels of the regulator were not affected by any of the growth conditions tested, the transcription of fruB was stimulated by fructose but not by the gluconeogenic substrate, succinate. The analysis of the P(fruB) promoter activity in a strain lacking the Cra protein and the determination of key metabolites revealed that this regulator represses the expression of PTS(Fru) in a fashion that is dependent on the endogenous concentrations of F1P. Because FruB (i.e. the EI-HPr-EIIA(Fru) polyprotein) can deliver a high-energy phosphate to the EIIA(Ntr) (PtsN) enzyme of the PTS(Ntr) branch, the cross-talk between the two phosphotransferase systems was examined under metabolic regimes that allowed for the high or low transcription of the fruBKA operon. While fructose caused cross-talk, succinate prevented it almost completely. Furthermore, PtsN phosphorylation by FruB occurred in a Δcra mutant regardless of growth conditions. These results traced the occurrence of the cross-talk to intracellular pools of Cra effectors, in particular F1P. The Cra/F1P duo seems to not only control the expression of the PTS(Fru) but also checks the activity of the PTS(Ntr) in vivo.
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Affiliation(s)
- Max Chavarría
- Systems Biology Program, Centro Nacional de Biotecnología, 28049 Cantoblanco-Madrid, Spain
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