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Rutkis R, Lasa Z, Rubina M, Strazdina I, Kalnenieks U. Eminent Antimicrobial Peptide Resistance in Zymomonas mobilis: A Novel Advantage of Intrinsically Uncoupled Energetics. Antibiotics (Basel) 2024; 13:451. [PMID: 38786179 PMCID: PMC11118514 DOI: 10.3390/antibiotics13050451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2024] [Revised: 05/08/2024] [Accepted: 05/10/2024] [Indexed: 05/25/2024] Open
Abstract
Relative to several model bacteria, the ethanologenic bacterium Zymomonas mobilis is shown here to have elevated resistance to exogenous antimicrobial peptides (AMPs)- with regard to both peptide bulk concentration in the medium and the numbers of peptide molecules per cell. By monitoring the integration of AMPs in the bacterial cell membrane and observing the resulting effect on membrane energy coupling, it is concluded that the membranotropic effects of the tested AMPs in Z. mobilis and in Escherichia coli are comparable. The advantage of Z. mobilis over E. coli apparently results from its uncoupled mode of energy metabolism that, in contrast to E. coli, does not rely on oxidative phosphorylation, and hence, is less vulnerable to the disruption of its energy-coupling membrane by AMPs. It is concluded that the high resistance to antimicrobial peptides (AMPs) observed in Z. mobilis not only proves crucial for its survival in its natural environment but also offers a promising platform for AMP production and sheds light on potential strategies for novel resistance development in clinical settings.
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Affiliation(s)
- Reinis Rutkis
- Institute of Microbiology and Biotechnology, University of Latvia, LV-1004 Riga, Latvia; (Z.L.); (M.R.); (U.K.)
| | - Zane Lasa
- Institute of Microbiology and Biotechnology, University of Latvia, LV-1004 Riga, Latvia; (Z.L.); (M.R.); (U.K.)
| | - Marta Rubina
- Institute of Microbiology and Biotechnology, University of Latvia, LV-1004 Riga, Latvia; (Z.L.); (M.R.); (U.K.)
| | - Inese Strazdina
- Institute of Microbiology and Biotechnology, University of Latvia, LV-1004 Riga, Latvia; (Z.L.); (M.R.); (U.K.)
| | - Uldis Kalnenieks
- Institute of Microbiology and Biotechnology, University of Latvia, LV-1004 Riga, Latvia; (Z.L.); (M.R.); (U.K.)
- Alternative Plants Ltd., LV-1007 Riga, Latvia
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Felczak MM, Bernard MP, TerAvest MA. Respiration is essential for aerobic growth of Zymomonas mobilis ZM4. mBio 2023; 14:e0204323. [PMID: 37909744 PMCID: PMC10746213 DOI: 10.1128/mbio.02043-23] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Accepted: 09/27/2023] [Indexed: 11/03/2023] Open
Abstract
IMPORTANCE A key to producing next-generation biofuels is to engineer microbes that efficiently convert non-food materials into drop-in fuels, and to engineer microbes effectively, we must understand their metabolism thoroughly. Zymomonas mobilis is a bacterium that is a promising candidate biofuel producer, but its metabolism remains poorly understood, especially its metabolism when exposed to oxygen. Although Z. mobilis respires with oxygen, its aerobic growth is poor, and disruption of genes related to respiration counterintuitively improves aerobic growth. This unusual result has sparked decades of research and debate regarding the function of respiration in Z. mobilis. Here, we used a new set of mutants to determine that respiration is essential for aerobic growth and likely protects the cells from damage caused by oxygen. We conclude that the respiratory pathway of Z. mobilis should not be deleted from chassis strains for industrial production because this would yield a strain that is intolerant of oxygen, which is more difficult to manage in industrial settings.
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Affiliation(s)
- Magdalena M. Felczak
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, USA
| | - Matthew P. Bernard
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan, USA
| | - Michaela A. TerAvest
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, USA
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3
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Enright AL, Banta AB, Ward RD, Rivera Vazquez J, Felczak MM, Wolfe MB, TerAvest MA, Amador-Noguez D, Peters JM. The genetics of aerotolerant growth in an alphaproteobacterium with a naturally reduced genome. mBio 2023; 14:e0148723. [PMID: 37905909 PMCID: PMC10746277 DOI: 10.1128/mbio.01487-23] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Accepted: 09/25/2023] [Indexed: 11/02/2023] Open
Abstract
IMPORTANCE The inherent complexity of biological systems is a major barrier to our understanding of cellular physiology. Bacteria with markedly fewer genes than their close relatives, or reduced genome bacteria, are promising biological models with less complexity. Reduced genome bacteria can also have superior properties for industrial use, provided the reduction does not overly restrict strain robustness. Naturally reduced genome bacteria, such as the alphaproteobacterium Zymomonas mobilis, have fewer genes but remain environmentally robust. In this study, we show that Z. mobilis is a simplified genetic model for Alphaproteobacteria, a class with important impacts on the environment, human health, and industry. We also identify genes that are only required in the absence of atmospheric oxygen, uncovering players that maintain and utilize the cellular energy state. Our findings have broad implications for the genetics of Alphaproteobacteria and industrial use of Z. mobilis to create biofuels and bioproducts.
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Affiliation(s)
- Amy L. Enright
- DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Amy B. Banta
- DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Ryan D. Ward
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Laboratory of Genetics, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Julio Rivera Vazquez
- DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Magdalena M. Felczak
- DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, USA
| | - Michael B. Wolfe
- DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Michaela A. TerAvest
- DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, USA
| | - Daniel Amador-Noguez
- DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Jason M. Peters
- DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Center for Genomic Science Innovation, University of Wisconsin-Madison, Madison, Wisconsin, USA
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4
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Improved Hydrogen Peroxide Stress Resistance of Zymomonas mobilis NADH Dehydrogenase (ndh) and Alcohol Dehydrogenase (adhB) Mutants. FERMENTATION-BASEL 2022. [DOI: 10.3390/fermentation8060289] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Unintended shifts in stress resistance of microbial strains with engineered central metabolism may impact their growth and production performance under oxidative, lignocellulosic, solvent, and other stress conditions, and as such, must be taken into account in bioprocess design. In the present work, we studied oxidative stress resistance in mutant strains of the facultatively anaerobic, ethanologenic bacterium Zymomonas mobilis with modified respiratory (inactivated NADH dehydrogenase Ndh, by disruption of ndh) and ethanologenic (inactivated iron-containing alcohol dehydrogenase isoenzyme ADH II, by disruption of adhB) catabolism, using exogenously added H2O2 in the concentration range of 2–6 mM as the oxidative stressor. Both mutations improved H2O2 resistance and enhanced catalase activity by a factor of 2–5, while the overexpression of Ndh had an opposite effect. Strains with a catalase-negative background were unable to grow already at 1 mM hydrogen peroxide, and their H2O2 resistance did not depend on AdhB or Ndh expression levels. Hence, the improved resistance of the ndh and adhB mutants to H2O2 resulted from their elevated catalase activity. The interrelation between these mutations, the catabolic redox balance, catalase activity, and oxidative stress defense in Z. mobilis is discussed.
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Antimicrobial Activity of Zymomonas mobilis Is Related to Its Aerobic Catabolism and Acid Resistance. FERMENTATION-BASEL 2022. [DOI: 10.3390/fermentation8020077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Zymomonas mobilis is an ethanologenic, facultatively anaerobic alpha-proteobacterium, known for its inhibitory effect on the growth of a wide variety of microorganisms. This property might be interesting for the design of novel antimicrobials, yet it has negative implications for biotechnology, as it hinders the use of Z. mobilis as a producer microorganism in cocultivation. So far, the chemical nature of its inhibitory compound(s) has not been established. In the present study, we demonstrate that the putative inhibitor is a low-molecular-weight (below 3 kDa), thermostable compound, resistant to protease treatment, which is synthesized under aerobic conditions in Z. mobilis strains via the active respiratory chain. It is also synthesized by aerated nongrowing, glucose-consuming cells in the presence of chloramphenicol, thus ruling out its bacteriocin-like peptide nature. The inhibitory activity is pH-dependent and strongly correlated with the accumulation of propionate and acetate in the culture medium. Although, in Z. mobilis, the synthesis pathways of these acids still need to be identified, the acid production depends on respiration, and is much less pronounced in the non-respiring mutant strain, which shows low inhibitory activity. We conclude that propionate and acetate play a central role in the antimicrobial effects of Z. mobilis, which itself is known to bear high resistance to organic acids.
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Braga A, Gomes D, Rainha J, Amorim C, Cardoso BB, Gudiña EJ, Silvério SC, Rodrigues JL, Rodrigues LR. Zymomonas mobilis as an emerging biotechnological chassis for the production of industrially relevant compounds. BIORESOUR BIOPROCESS 2021; 8:128. [PMID: 38650193 PMCID: PMC10992037 DOI: 10.1186/s40643-021-00483-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Accepted: 12/06/2021] [Indexed: 11/10/2022] Open
Abstract
Zymomonas mobilis is a well-recognized ethanologenic bacterium with outstanding characteristics which make it a promising platform for the biotechnological production of relevant building blocks and fine chemicals compounds. In the last years, research has been focused on the physiological, genetic, and metabolic engineering strategies aiming at expanding Z. mobilis ability to metabolize lignocellulosic substrates toward biofuel production. With the expansion of the Z. mobilis molecular and computational modeling toolbox, the potential of this bacterium as a cell factory has been thoroughly explored. The number of genomic, transcriptomic, proteomic, and fluxomic data that is becoming available for this bacterium has increased. For this reason, in the forthcoming years, systems biology is expected to continue driving the improvement of Z. mobilis for current and emergent biotechnological applications. While the existing molecular toolbox allowed the creation of stable Z. mobilis strains with improved traits for pinpointed biotechnological applications, the development of new and more flexible tools is crucial to boost the engineering capabilities of this bacterium. Novel genetic toolkits based on the CRISPR-Cas9 system and recombineering have been recently used for the metabolic engineering of Z. mobilis. However, they are mostly at the proof-of-concept stage and need to be further improved.
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Affiliation(s)
- Adelaide Braga
- CEB-Centre of Biological Engineering, Universidade Do Minho, Campus de Gualtar, 4710-057, Braga, Portugal
| | - Daniela Gomes
- CEB-Centre of Biological Engineering, Universidade Do Minho, Campus de Gualtar, 4710-057, Braga, Portugal
| | - João Rainha
- CEB-Centre of Biological Engineering, Universidade Do Minho, Campus de Gualtar, 4710-057, Braga, Portugal
| | - Cláudia Amorim
- CEB-Centre of Biological Engineering, Universidade Do Minho, Campus de Gualtar, 4710-057, Braga, Portugal
| | - Beatriz B Cardoso
- CEB-Centre of Biological Engineering, Universidade Do Minho, Campus de Gualtar, 4710-057, Braga, Portugal
| | - Eduardo J Gudiña
- CEB-Centre of Biological Engineering, Universidade Do Minho, Campus de Gualtar, 4710-057, Braga, Portugal
| | - Sara C Silvério
- CEB-Centre of Biological Engineering, Universidade Do Minho, Campus de Gualtar, 4710-057, Braga, Portugal
| | - Joana L Rodrigues
- CEB-Centre of Biological Engineering, Universidade Do Minho, Campus de Gualtar, 4710-057, Braga, Portugal
| | - Lígia R Rodrigues
- CEB-Centre of Biological Engineering, Universidade Do Minho, Campus de Gualtar, 4710-057, Braga, Portugal.
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Rutkis R, Strazdina I, Lasa Z, Bruheim P, Kalnenieks U. Ethanologenesis and respiration in a pyruvate decarboxylase-deficient Zymomonas mobilis. BMC Res Notes 2021; 14:208. [PMID: 34049566 PMCID: PMC8161578 DOI: 10.1186/s13104-021-05625-5] [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: 02/03/2021] [Accepted: 05/19/2021] [Indexed: 11/10/2022] Open
Abstract
Objective Zymomonas mobilis is an alpha-proteobacterium with a rapid ethanologenic pathway, involving Entner–Doudoroff (E–D) glycolysis, pyruvate decarboxylase (Pdc) and two alcohol dehydrogenase (ADH) isoenzymes. Pyruvate is the end-product of the E–D pathway and the substrate for Pdc. Construction and study of Pdc-deficient strains is of key importance for Z. mobilis metabolic engineering, because the pyruvate node represents the central branching point, most novel pathways divert from ethanol synthesis. In the present work, we examined the aerobic metabolism of a strain with partly inactivated Pdc. Results Relative to its parent strain the mutant produced more pyruvate. Yet, it also yielded more acetaldehyde, the product of the Pdc reaction and the substrate for ADH, although the bulk ADH activity was similar in both strains, while the Pdc activity in the mutant was reduced by half. Simulations with the kinetic model of Z. mobilis E-D pathway indicated that, for the observed acetaldehyde to ethanol production ratio in the mutant, the ratio between its respiratory NADH oxidase and ADH activities should be significantly higher, than the measured values. Implications of this finding for the directionality of the ADH isoenzyme operation in vivo and interactions between ADH and Pdc are discussed. Supplementary Information The online version contains supplementary material available at 10.1186/s13104-021-05625-5.
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Affiliation(s)
- Reinis Rutkis
- Institute of Microbiology and Biotechnology, University of Latvia, Riga, Latvia
| | - Inese Strazdina
- Institute of Microbiology and Biotechnology, University of Latvia, Riga, Latvia
| | - Zane Lasa
- Institute of Microbiology and Biotechnology, University of Latvia, Riga, Latvia
| | - Per Bruheim
- Department of Biotechnology and Food Science, NTNU Norwegian University of Science and Technology, Trondheim, Norway
| | - Uldis Kalnenieks
- Institute of Microbiology and Biotechnology, University of Latvia, Riga, Latvia.
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Ghaffarinasab S, Motamedian E. Improving ethanol production by studying the effect of pH using a modified metabolic model and a systemic approach. Biotechnol Bioeng 2021; 118:2934-2946. [PMID: 33913513 DOI: 10.1002/bit.27800] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 03/19/2021] [Accepted: 04/21/2021] [Indexed: 11/06/2022]
Abstract
pH is an important factor affecting the growth and production of microorganisms; especially, its effect on ethanologenic microorganisms. It can change the ionization state of metabolites via the change in the charge of their functional groups that may lead to metabolic alteration. Here, we estimated the ionization state of metabolites and balanced the charge of reactions in genome-scale metabolic models of Saccharomyces cerevisiae, Escherichia coli, and Zymomonas mobilis at pH levels 5, 6, and 7. The robustness analysis was first implemented to anticipate the effect of proton exchange flux on growth rates for the constructed metabolic models at various pH. In accordance with previous experimental reports, the models predict that Z. mobilis is more sensitive to pH rather than S. cerevisiae and the yeast is more regulated by pH rather than E. coli. Then, a systemic approach was proposed to predict the pH effect on metabolic change and to find effective reactions on ethanol production in S. cerevisiae. The correlated reactions with ethanol production at predicted optimal pH in a range of proton exchange rates determined by robustness analysis were identified using the Pearson correlation coefficient. Then, fluxes of these reactions were applied to cluster the various pHs by principal component analysis and to identify the role of these reactions on metabolic differentiation because of pH change. Finally, 12 reactions were selected for up and downregulation to improve ethanol production. Enzyme regulators of the selected reactions were identified using the BRENDA database and 11 selected regulators were screened and optimized via Plackett-Burman and two-level full factorial designs, respectively. The proposed approach has enhanced yields of ethanol from 0.18 to 0.36 mol/mol carbon. Hence, not only a comprehensive approach for understanding the effect of pH on metabolism was proposed in this study, but also it successfully introduced key manipulations for ethanol overproduction.
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Affiliation(s)
- Sajjad Ghaffarinasab
- Department of Biotechnology, Faculty of Chemical Engineering, Tarbiat Modares University, Tehran, Iran
| | - Ehsan Motamedian
- Department of Biotechnology, Faculty of Chemical Engineering, Tarbiat Modares University, Tehran, Iran
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Metabolic Profiling of Glucose-Fed Metabolically Active Resting Zymomonas mobilis Strains. Metabolites 2020; 10:metabo10030081. [PMID: 32110884 PMCID: PMC7142471 DOI: 10.3390/metabo10030081] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Revised: 02/17/2020] [Accepted: 02/24/2020] [Indexed: 11/17/2022] Open
Abstract
Zymomonas mobilis is the most efficient bacterial ethanol producer and its physiology is potentially applicable to industrial-scale bioethanol production. However, compared to other industrially important microorganisms, the Z. mobilis metabolome and adaptation to various nutritional and genetic perturbations have been poorly characterized. For rational metabolic engineering, it is essential to understand how central metabolism and intracellular redox balance are maintained in Z. mobilis under various conditions. In this study, we applied quantitative mass spectrometry-based metabolomics to explore how glucose-fed non-growing Z. mobilis Zm6 cells metabolically adapt to change of oxygen availability. Mutants partially impaired in ethanol synthesis (Zm6 adhB) or oxidative stress response (Zm6 cat) were also examined. Distinct patterns of adaptation of central metabolite pools due to the change in cultivation condition and between the mutants and Zm6 reference strain were observed. Decreased NADH/NAD ratio under aerobic incubation corresponded to higher concentrations of the phosphorylated glycolytic intermediates, in accordance with predictions of the kinetic model of Entner–Doudoroff pathway. The effects on the metabolite pools of aerobic to anaerobic transition were similar in the mutants, yet less pronounced. The present data on metabolic plasticity of non-growing Z. mobilis cells will facilitate the further metabolic engineering of the respective strains and their application as biocatalysts.
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Yang Q, Yang Y, Tang Y, Wang X, Chen Y, Shen W, Zhan Y, Gao J, Wu B, He M, Chen S, Yang S. Development and characterization of acidic-pH-tolerant mutants of Zymomonas mobilis through adaptation and next-generation sequencing-based genome resequencing and RNA-Seq. BIOTECHNOLOGY FOR BIOFUELS 2020; 13:144. [PMID: 32817760 PMCID: PMC7427070 DOI: 10.1186/s13068-020-01781-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Accepted: 08/04/2020] [Indexed: 05/19/2023]
Abstract
BACKGROUND Acid pretreatment is a common strategy used to break down the hemicellulose component of the lignocellulosic biomass to release pentoses, and a subsequent enzymatic hydrolysis step is usually applied to release hexoses from the cellulose. The hydrolysate after pretreatment and enzymatic hydrolysis containing both hexoses and pentoses can then be used as substrates for biochemical production. However, the acid-pretreated liquor can also be directly used as the substrate for microbial fermentation, which has an acidic pH and contains inhibitory compounds generated during pretreatment. Although the natural ethanologenic bacterium Zymomonas mobilis can grow in a broad range of pH 3.5 ~ 7.5, cell growth and ethanol fermentation are still affected under acidic-pH conditions below pH 4.0. RESULTS In this study, adaptive laboratory evolution (ALE) strategy was applied to adapt Z. mobilis under acidic-pH conditions. Two mutant strains named 3.6M and 3.5M with enhanced acidic pH tolerance were selected and confirmed, of which 3.5M grew better than ZM4 but worse than 3.6M in acidic-pH conditions that is served as a reference strain between 3.6M and ZM4 to help unravel the acidic-pH tolerance mechanism. Mutant strains 3.5M and 3.6M exhibited 50 ~ 130% enhancement on growth rate, 4 ~ 9 h reduction on fermentation time to consume glucose, and 20 ~ 63% improvement on ethanol productivity than wild-type ZM4 at pH 3.8. Next-generation sequencing (NGS)-based whole-genome resequencing (WGR) and RNA-Seq technologies were applied to unravel the acidic-pH tolerance mechanism of mutant strains. WGR result indicated that compared to wild-type ZM4, 3.5M and 3.6M have seven and five single nucleotide polymorphisms (SNPs), respectively, among which four are shared in common. Additionally, RNA-Seq result showed that the upregulation of genes involved in glycolysis and the downregulation of flagellar and mobility related genes would help generate and redistribute cellular energy to resist acidic pH while keeping normal biological processes in Z. mobilis. Moreover, genes involved in RND efflux pump, ATP-binding cassette (ABC) transporter, proton consumption, and alkaline metabolite production were significantly upregulated in mutants under the acidic-pH condition compared with ZM4, which could help maintain the pH homeostasis in mutant strains for acidic-pH resistance. Furthermore, our results demonstrated that in mutant 3.6M, genes encoding F1F0 ATPase to pump excess protons out of cells were upregulated under pH 3.8 compared to pH 6.2. This difference might help mutant 3.6M manage acidic conditions better than ZM4 and 3.5M. A few gene targets were then selected for genetics study to explore their role in acidic pH tolerance, and our results demonstrated that the expression of two operons in the shuttle plasmids, ZMO0956-ZMO0958 encoding cytochrome bc1 complex and ZMO1428-ZMO1432 encoding RND efflux pump, could help Z. mobilis tolerate acidic-pH conditions. CONCLUSION An acidic-pH-tolerant mutant 3.6M obtained through this study can be used for commercial bioethanol production under acidic fermentation conditions. In addition, the molecular mechanism of acidic pH tolerance of Z. mobilis was further proposed, which can facilitate future research on rational design of synthetic microorganisms with enhanced tolerance against acidic-pH conditions. Moreover, the strategy developed in this study combining approaches of ALE, genome resequencing, RNA-Seq, and classical genetics study for mutant evolution and characterization can be applied in other industrial microorganisms.
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Affiliation(s)
- Qing Yang
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Environmental Microbial Technology Center of Hubei Province and School of Life Sciences, Hubei University, Wuhan, 430062 China
| | - Yongfu Yang
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Environmental Microbial Technology Center of Hubei Province and School of Life Sciences, Hubei University, Wuhan, 430062 China
| | - Ying Tang
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Environmental Microbial Technology Center of Hubei Province and School of Life Sciences, Hubei University, Wuhan, 430062 China
| | - Xia Wang
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Environmental Microbial Technology Center of Hubei Province and School of Life Sciences, Hubei University, Wuhan, 430062 China
| | - Yunhao Chen
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Environmental Microbial Technology Center of Hubei Province and School of Life Sciences, Hubei University, Wuhan, 430062 China
| | - Wei Shen
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Environmental Microbial Technology Center of Hubei Province and School of Life Sciences, Hubei University, Wuhan, 430062 China
| | - Yangyang Zhan
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Environmental Microbial Technology Center of Hubei Province and School of Life Sciences, Hubei University, Wuhan, 430062 China
| | - Junjie Gao
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Environmental Microbial Technology Center of Hubei Province and School of Life Sciences, Hubei University, Wuhan, 430062 China
| | - Bo Wu
- Key Laboratory of Development and Application of Rural Renewable Energy, Biomass Energy Technology Research Centre, Biogas Institute of Ministry of Agriculture, South Renmin Road, Chengdu, 610041 China
| | - Mingxiong He
- Key Laboratory of Development and Application of Rural Renewable Energy, Biomass Energy Technology Research Centre, Biogas Institute of Ministry of Agriculture, South Renmin Road, Chengdu, 610041 China
| | - Shouwen Chen
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Environmental Microbial Technology Center of Hubei Province and School of Life Sciences, Hubei University, Wuhan, 430062 China
| | - Shihui Yang
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Environmental Microbial Technology Center of Hubei Province and School of Life Sciences, Hubei University, Wuhan, 430062 China
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Zymomonas mobilis metabolism: Novel tools and targets for its rational engineering. Adv Microb Physiol 2020; 77:37-88. [PMID: 34756211 DOI: 10.1016/bs.ampbs.2020.08.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Zymomonas mobilis is an α-proteobacterium that interests the biofuel industry due to its perfect ethanol fermentation yields. From its first description as a bacterial isolate in fermented alcoholic beverages to date, Z. mobilis has been rigorously studied in directions basic and applied. The Z. mobilis powerful Entner-Doudoroff glycolytic pathway has been the center of rigorous biochemical studies and, aside from ethanol, it has attracted interest in terms of high-added-value chemical manufacturing. Energetic balances and the effects of respiration have been explored in fundamental directions as also in applications pursuing strain enhancement and the utilization of alternative carbon sources. Metabolic modeling has addressed the optimization of the biochemical circuitry at various conditions of growth and/or substrate utilization; it has been also critical in predicting desirable end-product yields via flux redirection. Lastly, stress tolerance has received particular attention, since it directly determines biocatalytical performance at challenging bioreactor conditions. At a genetic level, advances in the genetic engineering of the organism have brought forth beneficial manipulations in the Z. mobilis gene pool, e.g., knock-outs, knock-ins and gene stacking, aiming to broaden the metabolic repertoire and increase robustness. Recent omic and expressional studies shed light on the genomic content of the most applied strains and reveal landscapes of activity manifested at ambient or reactor-based conditions. Studies such as those reviewed in this work, contribute to the understanding of the biology of Z. mobilis, enable insightful strain development, and pave the way for the transformation of Z. mobilis into a consummate organism for biomass conversion.
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Kalnenieks U, Balodite E, Strähler S, Strazdina I, Rex J, Pentjuss A, Fuchino K, Bruheim P, Rutkis R, Pappas KM, Poole RK, Sawodny O, Bettenbrock K. Improvement of Acetaldehyde Production in Zymomonas mobilis by Engineering of Its Aerobic Metabolism. Front Microbiol 2019; 10:2533. [PMID: 31798541 PMCID: PMC6868117 DOI: 10.3389/fmicb.2019.02533] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Accepted: 10/21/2019] [Indexed: 01/29/2023] Open
Abstract
Acetaldehyde is a valuable product of microbial biosynthesis, which can be used by the chemical industry as the entry point for production of various commodity chemicals. In ethanologenic microorganisms, like yeast or the bacterium Zymomonas mobilis, this compound is the immediate metabolic precursor of ethanol. In aerobic cultures of Z. mobilis, it accumulates as a volatile, inhibitory byproduct, due to the withdrawal of reducing equivalents from the alcohol dehydrogenase reaction by respiration. The active respiratory chain of Z. mobilis with its low energy-coupling efficiency is well-suited for regeneration of NAD+ under conditions when acetaldehyde, but not ethanol, is the desired catabolic product. In the present work, we sought to improve the capacity Z. mobilis to synthesize acetaldehyde, based on predictions of a stoichiometric model of its central metabolism developed herein. According to the model analysis, the main objectives in the course of engineering acetaldehyde producer strains were determined to be: (i) reducing ethanol synthesis via reducing the activity of alcohol dehydrogenase (ADH), and (ii) enhancing the respiratory capacity, either by overexpression of the respiratory NADH dehydrogenase (NDH), or by mutation of other components of respiratory metabolism. Several mutants with elevated respiration rate, decreased alcohol dehydrogenase activity, or a combination of both, were obtained. They were extensively characterized by determining their growth rates, product yields, oxygen consumption rates, ADH, and NDH activities, transcription levels of key catabolic genes, as well as concentrations of central metabolites under aerobic culture conditions. Two mutant strains were selected, with acetaldehyde yield close to 70% of the theoretical maximum value, almost twice the previously published yield for Z. mobilis. These strains can serve as a basis for further development of industrial acetaldehyde producers.
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Affiliation(s)
- Uldis Kalnenieks
- Institute of Microbiology and Biotechnology, University of Latvia, Riga, Latvia
| | - Elina Balodite
- Institute of Microbiology and Biotechnology, University of Latvia, Riga, Latvia
| | - Steffi Strähler
- Max-Planck-Institute for Dynamics of Complex Technical Systems, Analysis and Redesign of Biological Networks, Magdeburg, Germany
| | - Inese Strazdina
- Institute of Microbiology and Biotechnology, University of Latvia, Riga, Latvia
| | - Julia Rex
- Institute for System Dynamics, University of Stuttgart, Stuttgart, Germany
| | - Agris Pentjuss
- Institute of Microbiology and Biotechnology, University of Latvia, Riga, Latvia
| | - Katsuya Fuchino
- Department of Biotechnology and Food Science, NTNU Norwegian University of Science and Technology, Trondheim, Norway
| | - Per Bruheim
- Department of Biotechnology and Food Science, NTNU Norwegian University of Science and Technology, Trondheim, Norway
| | - Reinis Rutkis
- Institute of Microbiology and Biotechnology, University of Latvia, Riga, Latvia
| | - Katherine M Pappas
- Department of Genetics and Biotechnology, Faculty of Biology, National and Kapodistrian University of Athens (NKUA), Athens, Greece
| | - Robert K Poole
- Department of Molecular Biology and Biotechnology, The Krebs Institute, University of Sheffield, Sheffield, United Kingdom
| | - Oliver Sawodny
- Institute for System Dynamics, University of Stuttgart, Stuttgart, Germany
| | - Katja Bettenbrock
- Max-Planck-Institute for Dynamics of Complex Technical Systems, Analysis and Redesign of Biological Networks, Magdeburg, Germany
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13
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Kalnenieks U, Balodite E, Rutkis R. Metabolic Engineering of Bacterial Respiration: High vs. Low P/O and the Case of Zymomonas mobilis. Front Bioeng Biotechnol 2019; 7:327. [PMID: 31781557 PMCID: PMC6861446 DOI: 10.3389/fbioe.2019.00327] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 10/28/2019] [Indexed: 11/13/2022] Open
Abstract
Respiratory chain plays a pivotal role in the energy and redox balance of aerobic bacteria. By engineering respiration, it is possible to alter the efficiency of energy generation and intracellular redox state, and thus affect the key bioprocess parameters: cell yield, productivity and stress resistance. Here we summarize the current metabolic engineering and synthetic biology approaches to bacterial respiratory metabolism, with a special focus on the respiratory chain of the ethanologenic bacterium Zymomonas mobilis. Electron transport in Z. mobilis can serve as a model system of bacterial respiration with low oxidative phosphorylation efficiency. Its application for redox balancing and relevance for improvement of stress tolerance are analyzed.
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Affiliation(s)
- Uldis Kalnenieks
- Institute of Microbiology and Biotechnology, University of Latvia, Riga, Latvia
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14
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Strazdina I, Balodite E, Lasa Z, Rutkis R, Galinina N, Kalnenieks U. Aerobic catabolism and respiratory lactate bypass in Ndh-negative Zymomonas mobilis. Metab Eng Commun 2018; 7:e00081. [PMID: 30591903 PMCID: PMC6260413 DOI: 10.1016/j.mec.2018.e00081] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Revised: 11/10/2018] [Accepted: 11/10/2018] [Indexed: 12/19/2022] Open
Abstract
Ability to ferment in the presence of oxygen increases the robustness of bioprocesses and opens opportunity for novel industrial setups. The ethanologenic bacterium Zymomonas mobilis performs rapid and efficient anaerobic ethanol fermentation, yet its respiratory NADH dehydrogenase (Ndh)-deficient strain (ndh-) is known to produce ethanol with high yield also under oxic conditions. Compared to the wild type, it has a lower rate of oxygen consumption, and an increased expression of the respiratory lactate dehydrogenase (Ldh). Here we present a quantitative study of the product spectrum and carbon balance for aerobically growing ndh-. Ldh-deficient and Ldh-overexpressing ndh- strains were constructed and used to examine the putative role of the respiratory lactate bypass for aerobic growth and production. We show that aerobically growing ndh- strains perform fermentative metabolism with a near-maximum ethanol yield, irrespective of their Ldh expression background. Yet, Ldh activity strongly affects the aerobic product spectrum in glucose-consuming non-growing cells. Also, Ldh-deficiency hampers growth at elevated temperature (42 °C) and delays the restart of growth after 10-15 h of aerobic starvation.
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Affiliation(s)
| | | | | | | | | | - Uldis Kalnenieks
- Institute of Microbiology and Biotechnology, University of Latvia, Jelgavas street 1, Riga LV-1004, Latvia
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15
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Wang X, He Q, Yang Y, Wang J, Haning K, Hu Y, Wu B, He M, Zhang Y, Bao J, Contreras LM, Yang S. Advances and prospects in metabolic engineering of Zymomonas mobilis. Metab Eng 2018; 50:57-73. [PMID: 29627506 DOI: 10.1016/j.ymben.2018.04.001] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Revised: 03/31/2018] [Accepted: 04/01/2018] [Indexed: 12/22/2022]
Abstract
Biorefinery of biomass-based biofuels and biochemicals by microorganisms is a competitive alternative of traditional petroleum refineries. Zymomonas mobilis is a natural ethanologen with many desirable characteristics, which makes it an ideal industrial microbial biocatalyst for commercial production of desirable bioproducts through metabolic engineering. In this review, we summarize the metabolic engineering progress achieved in Z. mobilis to expand its substrate and product ranges as well as to enhance its robustness against stressful conditions such as inhibitory compounds within the lignocellulosic hydrolysates and slurries. We also discuss a few metabolic engineering strategies that can be applied in Z. mobilis to further develop it as a robust workhorse for economic lignocellulosic bioproducts. In addition, we briefly review the progress of metabolic engineering in Z. mobilis related to the classical synthetic biology cycle of "Design-Build-Test-Learn", as well as the progress and potential to develop Z. mobilis as a model chassis for biorefinery practices in the synthetic biology era.
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Affiliation(s)
- Xia Wang
- Hubei Collaborative Innovation Center for Green Transformation of Bio-resources, Environmental Microbial Technology Center of Hubei Province, Hubei Key Laboratory of Industrial Biotechnology, College of Life Sciences, Hubei University, Wuhan 430062, China.
| | - Qiaoning He
- Hubei Collaborative Innovation Center for Green Transformation of Bio-resources, Environmental Microbial Technology Center of Hubei Province, Hubei Key Laboratory of Industrial Biotechnology, College of Life Sciences, Hubei University, Wuhan 430062, China.
| | - Yongfu Yang
- Hubei Collaborative Innovation Center for Green Transformation of Bio-resources, Environmental Microbial Technology Center of Hubei Province, Hubei Key Laboratory of Industrial Biotechnology, College of Life Sciences, Hubei University, Wuhan 430062, China.
| | - Jingwen Wang
- Hubei Collaborative Innovation Center for Green Transformation of Bio-resources, Environmental Microbial Technology Center of Hubei Province, Hubei Key Laboratory of Industrial Biotechnology, College of Life Sciences, Hubei University, Wuhan 430062, China.
| | - Katie Haning
- Institute for Cellular and Molecular Biology, Department of Chemical Engineering, Cockrell School of Engineering, University of Texas at Austin, Austin, TX, United States.
| | - Yun Hu
- Hubei Collaborative Innovation Center for Green Transformation of Bio-resources, Environmental Microbial Technology Center of Hubei Province, Hubei Key Laboratory of Industrial Biotechnology, College of Life Sciences, Hubei University, Wuhan 430062, China.
| | - Bo Wu
- Key Laboratory of Development and Application of Rural Renewable Energy, Biomass Energy Technology Research Centre, Biogas Institute of Ministry of Agriculture, South Renmin Road, Chengdu 610041, China.
| | - Mingxiong He
- Key Laboratory of Development and Application of Rural Renewable Energy, Biomass Energy Technology Research Centre, Biogas Institute of Ministry of Agriculture, South Renmin Road, Chengdu 610041, China.
| | - Yaoping Zhang
- DOE-Great Lakes Bioenergy Research Center (GLBRC), University of Wisconsin-Madison, Madison, WI, United States.
| | - Jie Bao
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China.
| | - Lydia M Contreras
- Institute for Cellular and Molecular Biology, Department of Chemical Engineering, Cockrell School of Engineering, University of Texas at Austin, Austin, TX, United States.
| | - Shihui Yang
- Hubei Collaborative Innovation Center for Green Transformation of Bio-resources, Environmental Microbial Technology Center of Hubei Province, Hubei Key Laboratory of Industrial Biotechnology, College of Life Sciences, Hubei University, Wuhan 430062, China.
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16
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Rutkis R, Strazdina I, Balodite E, Lasa Z, Galinina N, Kalnenieks U. The Low Energy-Coupling Respiration in Zymomonas mobilis Accelerates Flux in the Entner-Doudoroff Pathway. PLoS One 2016; 11:e0153866. [PMID: 27100889 PMCID: PMC4839697 DOI: 10.1371/journal.pone.0153866] [Citation(s) in RCA: 24] [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: 11/13/2015] [Accepted: 04/05/2016] [Indexed: 11/18/2022] Open
Abstract
Performing oxidative phosphorylation is the primary role of respiratory chain both in bacteria and eukaryotes. Yet, the branched respiratory chains of prokaryotes contain alternative, low energy-coupling electron pathways, which serve for functions other than oxidative ATP generation (like those of respiratory protection, adaptation to low-oxygen media, redox balancing, etc.), some of which are still poorly understood. We here demonstrate that withdrawal of reducing equivalents by the energetically uncoupled respiratory chain of the bacterium Zymomonas mobilis accelerates its fermentative catabolism, increasing the glucose consumption rate. This is in contrast to what has been observed in other respiring bacteria and yeast. This effect takes place after air is introduced to glucose-consuming anaerobic cell suspension, and can be simulated using a kinetic model of the Entner-Doudoroff pathway in combination with a simple net reaction of NADH oxidation that does not involve oxidative phosphorylation. Although aeration hampers batch growth of respiring Z. mobilis culture due to accumulation of toxic byproducts, nevertheless under non-growing conditions respiration is shown to confer an adaptive advantage for the wild type over the non-respiring Ndh knock-out mutant. If cells get occasional access to limited amount of glucose for short periods of time, the elevated glucose uptake rate selectively improves survival of the respiring Z. mobilis phenotype.
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Affiliation(s)
- Reinis Rutkis
- Institute of Microbiology and Biotechnology, University of Latvia, Jelgavas Street 1, Riga, LV-1004, Latvia
| | - Inese Strazdina
- Institute of Microbiology and Biotechnology, University of Latvia, Jelgavas Street 1, Riga, LV-1004, Latvia
| | - Elina Balodite
- Institute of Microbiology and Biotechnology, University of Latvia, Jelgavas Street 1, Riga, LV-1004, Latvia
| | - Zane Lasa
- Institute of Microbiology and Biotechnology, University of Latvia, Jelgavas Street 1, Riga, LV-1004, Latvia
| | - Nina Galinina
- Institute of Microbiology and Biotechnology, University of Latvia, Jelgavas Street 1, Riga, LV-1004, Latvia
| | - Uldis Kalnenieks
- Institute of Microbiology and Biotechnology, University of Latvia, Jelgavas Street 1, Riga, LV-1004, Latvia
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17
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Motamedian E, Saeidi M, Shojaosadati SA. Reconstruction of a charge balanced genome-scale metabolic model to study the energy-uncoupled growth of Zymomonas mobilis ZM1. MOLECULAR BIOSYSTEMS 2016; 12:1241-9. [DOI: 10.1039/c5mb00588d] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Zymomonas mobilisis an ethanologenic bacterium and is known to be an example microorganism with energy-uncoupled growth. The reconstructed metabolic model indicate that resistance to intracellular pH reduction could be the main reason for uncoupled growth.
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Affiliation(s)
- E. Motamedian
- Biotechnology Group
- Chemical Engineering Department
- Tarbiat Modares University
- Tehran
- Iran
| | - M. Saeidi
- Biotechnology Group
- Chemical Engineering Department
- Tarbiat Modares University
- Tehran
- Iran
| | - S. A. Shojaosadati
- Biotechnology Group
- Chemical Engineering Department
- Tarbiat Modares University
- Tehran
- Iran
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18
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Hayashi T, Kato T, Watakabe S, Song W, Aikawa S, Furukawa K. The respiratory chain provides salt stress tolerance by maintaining a low NADH/NAD+ ratio in Zymomonas mobilis. MICROBIOLOGY-SGM 2015; 161:2384-94. [PMID: 26432557 DOI: 10.1099/mic.0.000195] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The respiratory chain of ethanol-producing Zymomonas mobilis shows an unusual physiological property in that it is not involved in energy conservation, even though this organism has a complete electron transport system. We reported previously that respiratory-deficient mutants (RDMs) of Z. mobilis exhibit higher growth rates and enhanced ethanol productivity under aerobic and high-temperature conditions. Here, we demonstrated that the salt tolerance of RDM strains was drastically decreased compared with the wild-type strain. We found that the NADH/NAD+ ratio was maintained at low levels in both the wild-type and the RDM strains under non-stress conditions. However, the ratio substantially increased in the RDM strains in response to salt stress. Complementation of the deficient respiratory-chain genes in the RDM strains resulted in a decrease in the NADH/NAD+ ratio and an increase in the growth rate. In contrast, expression of malate dehydrogenase, activity of which increases the supply of NADH, in the RDM strains led to an increased NADH/NAD+ ratio and resulted in poor growth. Taken together, these results suggest that the respiratory chain of Z. mobilis functions to maintain a low NADH/NAD+ ratio when the cells are exposed to environmental stresses, such as salinity.
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Affiliation(s)
- Takeshi Hayashi
- 1Department of Food and Fermentation Science, Faculty of Food and Nutrition, Beppu University, Beppu, Oita 874-8501, Japan 2Food Science and Nutrition, Graduate School of Food Science and Nutrition, Beppu University, Beppu, Oita 874-8501, Japan
| | - Tsuyoshi Kato
- 2Food Science and Nutrition, Graduate School of Food Science and Nutrition, Beppu University, Beppu, Oita 874-8501, Japan
| | - Satoshi Watakabe
- 1Department of Food and Fermentation Science, Faculty of Food and Nutrition, Beppu University, Beppu, Oita 874-8501, Japan
| | - Wonjoon Song
- 1Department of Food and Fermentation Science, Faculty of Food and Nutrition, Beppu University, Beppu, Oita 874-8501, Japan
| | - Shizuho Aikawa
- 1Department of Food and Fermentation Science, Faculty of Food and Nutrition, Beppu University, Beppu, Oita 874-8501, Japan
| | - Kensuke Furukawa
- 1Department of Food and Fermentation Science, Faculty of Food and Nutrition, Beppu University, Beppu, Oita 874-8501, Japan
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