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Strazdina I, Klavins L, Galinina N, Shvirksts K, Grube M, Stalidzans E, Kalnenieks U. Syntrophy of Crypthecodinium cohnii and immobilized Zymomonas mobilis for docosahexaenoic acid production from sucrose-containing substrates. J Biotechnol 2021; 338:63-70. [PMID: 34280360 DOI: 10.1016/j.jbiotec.2021.07.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2021] [Revised: 07/10/2021] [Accepted: 07/13/2021] [Indexed: 11/17/2022]
Abstract
Marine heterotrophic dinoflagellate Crypthecodinium cohnii is an aerobic oleaginous microorganism that accumulates intracellular lipid with high content of 4,7,10,13,16,19-docosahexaenoic acid (DHA), a polyunsaturated ω-3 (22:6) fatty acid with multiple health benefits. C. cohnii can grow on glucose and ethanol, but not on sucrose or fructose. For conversion of sucrose-containing renewables to C. cohnii DHA, we investigated a syntrophic process, involving immobilized cells of ethanologenic bacterium Zymomonas mobilis for fermenting sucrose to ethanol. The non-respiring, NADH dehydrogenase-deficient Z. mobilis strain Zm6-ndh, with high ethanol yield both under anaerobic and aerobic conditions, was taken as the genetic background for inactivation of levansucrase (sacB). SacB mutation eliminated the levan-forming activity on sucrose. The double mutant Zm6-ndh-sacB cells were immobilized in Ca alginate, and applied for syntrophic conversion of sucrose to DHA of C. cohnii, either taking the ethanol-containing fermentation medium from the immobilized Z. mobilis for feeding to the C. cohnii fed-batch culture, or directly coculturing the immobilized Zm6-ndh-sacB with C. cohnii on sucrose. Both modes of cultivation produced C. cohnii CCMP 316 biomass with DHA content around 2-3 % of cell dry weight, corresponding to previously reported results for this strain on glucose.
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Affiliation(s)
- Inese Strazdina
- University of Latvia, Institute of Microbiology and Biotechnology, Riga, Latvia
| | - Linards Klavins
- University of Latvia, Natural Resource Research Centre, Riga, Latvia
| | - Nina Galinina
- University of Latvia, Institute of Microbiology and Biotechnology, Riga, Latvia
| | - Karlis Shvirksts
- University of Latvia, Institute of Microbiology and Biotechnology, Riga, Latvia
| | - Mara Grube
- University of Latvia, Institute of Microbiology and Biotechnology, Riga, Latvia
| | - Egils Stalidzans
- University of Latvia, Institute of Microbiology and Biotechnology, Riga, Latvia
| | - Uldis Kalnenieks
- University of Latvia, Institute of Microbiology and Biotechnology, Riga, Latvia.
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Balodite E, Strazdina I, Martynova J, Galinina N, Rutkis R, Lasa Z, Kalnenieks U. Translocation of Zymomonas mobilis pyruvate decarboxylase to periplasmic compartment for production of acetaldehyde outside the cytosol. Microbiologyopen 2019; 8:e00809. [PMID: 30770675 PMCID: PMC6692523 DOI: 10.1002/mbo3.809] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 01/11/2019] [Accepted: 01/12/2019] [Indexed: 11/13/2022] Open
Abstract
Acetaldehyde, a valuable commodity chemical, is a volatile inhibitory byproduct of aerobic fermentation in Zymomonas mobilis and in several other microorganisms. Attempting to improve acetaldehyde production by minimizing its contact with the cell interior and facilitating its removal from the culture, we engineered a Z. mobilis strain with acetaldehyde synthesis reaction localized in periplasm. For that, the pyruvate decarboxylase (PDC) was transferred from the cell interior to the periplasmic compartment. This was achieved by the construction of a Z. mobilis Zm6 PDC‐deficient mutant, fusion of PDC with the periplasmic signal sequence of Z. mobilis gluconolactonase, and the following expression of this fusion protein in the PDC‐deficient mutant. The obtained recombinant strain PeriAc, with most of its PDC localized in periplasm, showed a twofold higher acetaldehyde yield, than the parent strain, and will be used for further improvement by directed evolution.
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Affiliation(s)
- Elina Balodite
- Institute of Microbiology and Biotechnology, University of Latvia, Riga, Latvia
| | - Inese Strazdina
- Institute of Microbiology and Biotechnology, University of Latvia, Riga, Latvia
| | | | - Nina Galinina
- Institute of Microbiology and Biotechnology, University of Latvia, Riga, Latvia
| | - Reinis Rutkis
- Institute of Microbiology and Biotechnology, University of Latvia, Riga, Latvia
| | - Zane Lasa
- Institute of Microbiology and Biotechnology, University of Latvia, Riga, Latvia
| | - Uldis Kalnenieks
- Institute of Microbiology and Biotechnology, University of Latvia, Riga, Latvia
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Balodite E, Strazdina I, Galinina N, McLean S, Rutkis R, Poole RK, Kalnenieks U. Structure of the Zymomonas mobilis respiratory chain: oxygen affinity of electron transport and the role of cytochrome c peroxidase. Microbiology (Reading) 2014; 160:2045-2052. [PMID: 24980645 PMCID: PMC4148688 DOI: 10.1099/mic.0.081612-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/08/2014] [Accepted: 06/12/2014] [Indexed: 11/30/2022]
Abstract
The genome of the ethanol-producing bacterium Zymomonas mobilis encodes a bd-type terminal oxidase, cytochrome bc1 complex and several c-type cytochromes, yet lacks sequences homologous to any of the known bacterial cytochrome c oxidase genes. Recently, it was suggested that a putative respiratory cytochrome c peroxidase, receiving electrons from the cytochrome bc1 complex via cytochrome c552, might function as a peroxidase and/or an alternative oxidase. The present study was designed to test this hypothesis, by construction of a cytochrome c peroxidase mutant (Zm6-perC), and comparison of its properties with those of a mutant defective in the cytochrome b subunit of the bc1 complex (Zm6-cytB). Disruption of the cytochrome c peroxidase gene (ZZ60192) caused a decrease of the membrane NADH peroxidase activity, impaired the resistance of growing culture to exogenous hydrogen peroxide and hampered aerobic growth. However, this mutation did not affect the activity or oxygen affinity of the respiratory chain, or the kinetics of cytochrome d reduction. Furthermore, the peroxide resistance and membrane NADH peroxidase activity of strain Zm6-cytB had not decreased, but both the oxygen affinity of electron transport and the kinetics of cytochrome d reduction were affected. It is therefore concluded that the cytochrome c peroxidase does not terminate the cytochrome bc1 branch of Z. mobilis, and that it is functioning as a quinol peroxidase.
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Affiliation(s)
- Elina Balodite
- Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda boulv. 4, 1586 Riga, Latvia
| | - Inese Strazdina
- Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda boulv. 4, 1586 Riga, Latvia
| | - Nina Galinina
- Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda boulv. 4, 1586 Riga, Latvia
| | - Samantha McLean
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK
| | - Reinis Rutkis
- Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda boulv. 4, 1586 Riga, Latvia
| | - Robert K. Poole
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK
| | - Uldis Kalnenieks
- Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda boulv. 4, 1586 Riga, Latvia
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Rutkis R, Galinina N, Strazdina I, Kalnenieks U. The inefficient aerobic energetics of Zymomonas mobilis: identifying the bottleneck. J Basic Microbiol 2014; 54:1090-7. [PMID: 24599704 DOI: 10.1002/jobm.201300859] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Accepted: 02/07/2014] [Indexed: 11/09/2022]
Abstract
To investigate the mechanisms of Zymomonas mobilis uncoupled aerobic metabolism, growth properties of the wild-type strain Zm6 were compared to those of its respiratory mutants cytB and cydB, and the effects of the ATPase inhibitor DCCD on growth and intracellular ATP concentration were studied. The effects of the ATPase inhibitor DCCD on growth and intracellular ATP concentration strongly indicated that the apparent lack of oxidative phosphorylation in aerobically growing Z. mobilis culture might be caused by the ATP hydrolyzing activity of the H(+) -dependent ATPase in all analyzed strains. Aerobic growth yields of the mutants, and their capacity of oxidative ATP synthesis with ethanol were closely similar, not supporting presence of one major, yet energetically inefficient electron transport branch causing the observed poor aerobic growth and lack of oxidative phosphorylation in Z. mobilis. We suggest that rapidly operating Entner-Doudoroff pathway generates too high phosphorylation potential for the weakly coupled respiratory system to shift the H(+) -dependent ATPase toward ATP synthesis.
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Affiliation(s)
- Reinis Rutkis
- Institute of Microbiology and Biotechnology, University of Latvia, Riga, Latvia
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Galinina N, Lasa Z, Strazdina I, Rutkis R, Kalnenieks U. Effect of ADH II deficiency on the intracellular redox homeostasis in Zymomonas mobilis. ScientificWorldJournal 2012; 2012:742610. [PMID: 22629192 PMCID: PMC3354707 DOI: 10.1100/2012/742610] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2011] [Accepted: 12/07/2011] [Indexed: 01/11/2023] Open
Abstract
Mutant strain of the facultatively anaerobic, ethanol-producing bacterium Zymomonas mobilis, deficient in the Fe-containing alcohol dehydrogenase isoenzyme (ADH II), showed impaired homeostasis of the intracellular NAD(P)H during transition from anaerobic to aerobic conditions, and also in steady-state continuous cultures at various oxygen supplies. At the same time, ADH II deficiency in aerobically grown cells was accompanied by a threefold increase of catalase activity and by about 50% increase of hydrogen peroxide excretion. It is concluded that ADH II under aerobic conditions functions to maintain intracellular redox homeostasis and to protect the cells from endogenous hydrogen peroxide.
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Affiliation(s)
- Nina Galinina
- Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda Boulevard 4, 1586 Riga, Latvia
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Strazdina I, Kravale Z, Galinina N, Rutkis R, Poole RK, Kalnenieks U. Electron transport and oxidative stress in Zymomonas mobilis respiratory mutants. Arch Microbiol 2012; 194:461-71. [PMID: 22228443 DOI: 10.1007/s00203-011-0785-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Revised: 11/19/2011] [Accepted: 12/16/2011] [Indexed: 10/14/2022]
Abstract
The ethanol-producing bacterium Zymomonas mobilis is of great interest from a bioenergetic perspective because, although it has a very high respiratory capacity, the respiratory system does not appear to be primarily required for energy conservation. To investigate the regulation of respiratory genes and function of electron transport branches in Z. mobilis, several mutants of the common wild-type strain Zm6 (ATCC 29191) were constructed and analyzed. Mutant strains with a chloramphenicol-resistance determinant inserted in the genes encoding the cytochrome b subunit of the bc (1) complex (Zm6-cytB), subunit II of the cytochrome bd terminal oxidase (Zm6-cydB), and in the catalase gene (Zm6-kat) were constructed. The cytB and cydB mutants had low respiration capacity when cultivated anaerobically. Zm6-cydB lacked the cytochrome d absorbance at 630 nm, while Zm6-cytB had very low spectral signals of all cytochromes and low catalase activity. However, under aerobic growth conditions, the respiration capacity of the mutant cells was comparable to that of the parent strain. The catalase mutation did not affect aerobic growth, but rendered cells sensitive to hydrogen peroxide. Cytochrome c peroxidase activity could not be detected. An upregulation of several thiol-dependent oxidative stress-protective systems was observed in an aerobically growing ndh mutant deficient in type II NADH dehydrogenase (Zm6-ndh). It is concluded that the electron transport chain in Z. mobilis contains at least two electron pathways to oxygen and that one of its functions might be to prevent endogenous oxidative stress.
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Affiliation(s)
- Inese Strazdina
- Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda boulv. 4, 1586 Riga, Latvia
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Kalnenieks U, Galinina N, Strazdina I, Kravale Z, Pickford JL, Rutkis R, Poole RK. NADH dehydrogenase deficiency results in low respiration rate and improved aerobic growth of Zymomonas mobilis. Microbiology (Reading) 2008; 154:989-994. [PMID: 18310045 DOI: 10.1099/mic.0.2007/012682-0] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The respiratory chain of the ethanol-producing bacterium Zymomonas mobilis is able to oxidize both species of nicotinamide cofactors, NADH and NADPH. A mutant strain with a chloramphenicol-resistance determinant inserted in ndh (encoding an NADH : CoQ oxidoreductase of type II) lacked the membrane NADH and NADPH oxidase activities, while its respiratory D-lactate oxidase activity was increased. Cells of the mutant strain showed a very low respiration rate with glucose and no respiration with ethanol. The aerobic growth rate of the mutant was elevated; exponential growth persisted longer, resulting in higher biomass densities. For the parent strain a similar effect of aerobic growth stimulation was achieved previously in the presence of submillimolar cyanide concentrations. It is concluded (i) that the respiratory chain of Z. mobilis contains only one functional NAD(P)H dehydrogenase, product of the ndh gene, and (ii) that inhibition of respiration, whether resulting from a mutation or from inhibitor action, stimulates Z. mobilis aerobic growth due to redirection of the NADH flux from respiration to ethanol synthesis, thus minimizing accumulation of toxic intermediates by contributing to the reduction of acetaldehyde to ethanol.
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Affiliation(s)
- Uldis Kalnenieks
- Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda Boulv. 4, LV-1586, Riga, Latvia
| | - Nina Galinina
- Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda Boulv. 4, LV-1586, Riga, Latvia
| | - Inese Strazdina
- Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda Boulv. 4, LV-1586, Riga, Latvia
| | - Zane Kravale
- Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda Boulv. 4, LV-1586, Riga, Latvia
| | - James L Pickford
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK
| | - Reinis Rutkis
- Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda Boulv. 4, LV-1586, Riga, Latvia
| | - Robert K Poole
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK
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Kalnenieks U, Galinina N, Toma MM, Pickford JL, Rutkis R, Poole RK. Respiratory behaviour of aZymomonas mobilis adhB::kanrmutant supports the hypothesis of two alcohol dehydrogenase isoenzymes catalysing opposite reactions. FEBS Lett 2006; 580:5084-8. [PMID: 16950260 DOI: 10.1016/j.febslet.2006.08.034] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2006] [Revised: 08/09/2006] [Accepted: 08/11/2006] [Indexed: 10/24/2022]
Abstract
Perturbation of the aerobic steady-state in a chemostat culture of the ethanol-producing bacterium Zymomonas mobilis with a small pulse of ethanol causes a burst of ethanol oxidation, although the reactant ratio of the alcohol dehydrogenase (ADH) reaction ([NADH][acetaldehyde][H(+)])/([ethanol][NAD(+)]) remains above the K(eq) value. Simultaneous catalysis of ethanol synthesis and oxidation by the two ADH isoenzymes, residing in different redox microenvironments, has been proposed previously. In the present study, this hypothesis is verified by construction of an ADH-deficient strain and by demonstration that it lacks the oxidative burst in response to perturbation of its aerobic steady-state with ethanol.
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Affiliation(s)
- U Kalnenieks
- Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda Boulv. 4, LV-1586, Riga, Latvia.
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Kalnenieks U, Galinina N, Toma MM. Physiological regulation of the properties of alcohol dehydrogenase II (ADH II) of Zymomonas mobilis: NADH renders ADH II resistant to cyanide and aeration. Arch Microbiol 2005; 183:450-6. [PMID: 16027951 DOI: 10.1007/s00203-005-0023-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2005] [Revised: 05/10/2005] [Accepted: 06/17/2005] [Indexed: 10/25/2022]
Abstract
The variable cyanide-sensitivity of the iron-containing alcohol dehydrogenase isoenzyme (ADH II) of the ethanol-producing bacterium Zymomonas mobilis was studied. In aerobically grown permeabilized cells, cyanide caused gradual inhibition of ADH II, which was largely prevented by externally added NADH. Cyanide-sensitivity of ADH II was highest in cells grown under conditions of vigorous aeration, in which intracellular NADH concentration was low. Anaerobically grown bacteria, as well as those cultivated aerobically in the presence of cyanide, maintained higher intracellular NADH levels along with a more cyanide-resistant ADH II. It was demonstrated that cyanide acted as a competitive inhibitor of ADH II, competing with nicotinamide nucleotides. NADH increased both cyanide-resistance and oxygen-resistance of ADH II.
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Affiliation(s)
- Uldis Kalnenieks
- Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda boulv. 4, 1586 Riga, Latvia.
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Kalnenieks U, Toma MM, Galinina N, Poole RK. The paradoxical cyanide-stimulated respiration of Zymomonas mobilis: cyanide sensitivity of alcohol dehydrogenase (ADH II). Microbiology (Reading) 2003; 149:1739-1744. [PMID: 12855725 DOI: 10.1099/mic.0.26073-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The respiratory inhibitor cyanide stimulates growth of the ethanologenic bacterium Zymomonas mobilis, perhaps by diverting reducing equivalents from respiration to ethanol synthesis, thereby minimizing accumulation of toxic acetaldehyde. This study sought to identify cyanide-sensitive components of respiration. In aerobically grown, permeabilized Z. mobilis cells, addition of 200 microM cyanide caused gradual inhibition of ADH II, the iron-containing alcohol dehydrogenase isoenzyme, which, in aerobic cultures, might be oxidizing ethanol and supplying NADH to the respiratory chain. In membrane preparations, NADH oxidase was inhibited more rapidly, but to a lesser extent, than ADH II. The time-course of inhibition of whole-cell respiration resembled that of NADH oxidase, yet the inhibition was almost complete, and was accompanied by an increase of intracellular NADH concentration. Cyanide did not significantly affect the activity of ADH I, the zinc-containing alcohol dehydrogenase isoenzyme. When an aerobic batch culture was grown in the presence of 200 microM cyanide, cyanide-resistant ADH II activity was observed, its appearance correlating with the onset of respiration. It is concluded that the membrane-associated respiratory chain, but not ADH II, is responsible for the whole-cell cyanide sensitivity, while the cyanide-resistant ADH II is needed for respiration in the presence of cyanide, and represents an adaptive response of Z. mobilis to cyanide, analogous to the induction of alternative terminal oxidases in other bacteria.
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Affiliation(s)
- Uldis Kalnenieks
- Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda boulv. 4, LV-1586 Riga, Latvia
| | - Malda M Toma
- Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda boulv. 4, LV-1586 Riga, Latvia
| | - Nina Galinina
- Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda boulv. 4, LV-1586 Riga, Latvia
| | - Robert K Poole
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK
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Abstract
A novel redox cycle is suggested, performing interconversion between acetaldehyde and ethanol in aerobically growing ethanologenic bacterium Zymomonas mobilis. It is formed by the two alcohol dehydrogenase (ADH) isoenzymes simultaneously catalyzing opposite reactions. ADH I is catalyzing acetaldehyde reduction. The local reactant ratio at its active site probably is shifted towards ethanol synthesis due to direct channeling of NADH from glycolysis. ADH II is oxidizing ethanol. The net result of the cycle operation is NADH shuttling from glycolysis to the membrane respiratory chain, and ensuring flexible distribution of reducing equivalents between the ADH reaction and respiration.
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Affiliation(s)
- U Kalnenieks
- Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda boulv. 4, LV-1586, Riga, Latvia.
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Kalnenieks U, Galinina N, Toma MM, Poole RK. Cyanide inhibits respiration yet stimulates aerobic growth of Zymomonas mobilis. Microbiology (Reading) 2000; 146 ( Pt 6):1259-1266. [PMID: 10846205 DOI: 10.1099/00221287-146-6-1259] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Potassium cyanide at submillimolar concentrations (20-500 microM) inhibited the high respiration rates of aerobic cultures of Zymomonas mobilis but, remarkably, stimulated culture growth. In batch culture, after an extended lag phase, exponential growth persisted longer, resulting in higher biomass densities. In aerobic chemostat cultures, elevated biomass concentration was observed in the presence of cyanide. This growth stimulation effect is attributed to decreased production of the inhibitory metabolite acetaldehyde at lowered respiration rates, when more reducing equivalents are channelled to alcohol dehydrogenase. Growth in the presence of cyanide did not alter the membrane cytochrome content. In non-growing cyanide-preincubated cells, with ethanol as the respiratory substrate, cyanide increased ATP levels; in such cells, a large part of the cyanide-sensitive respiration was inhibited within a few seconds after ethanol addition, while inhibition of the rest of respiration took several minutes. The more cyanide-sensitive respiration was apparently energy-nongenerating, and was absent in membrane preparations. Pelleting of membranes from cell-free extracts produced 'soluble' fractions in which a b-type haem was detectable by reduced minus oxidized difference spectroscopy. The function of the Z. mobilis respiratory chain in cell growth and respiratory protection, and the possible physiological role of aerobic generation of inhibitory metabolites, are discussed.
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Affiliation(s)
- Uldis Kalnenieks
- Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda boulv. 4,Riga LV-1586, Latvia1
| | - Nina Galinina
- Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda boulv. 4,Riga LV-1586, Latvia1
| | - Malda M Toma
- Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda boulv. 4,Riga LV-1586, Latvia1
| | - Robert K Poole
- Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, S10 2TN Sheffield, UK2
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Abstract
Respiratory chain composition of the ethanol-producing bacterium Zymomonas mobilis was studied. Its membrane D-lactate oxidase was characterised. With NADH, but not D-lactate as substrate, a cytochrome o-like component was seen in CO difference spectra. Chlorpromazine specifically inhibited reduction of cytochrome d, while myxothiazol eliminated the cytochrome o-like features in CO difference spectra. It is suggested that electrons from NADH are distributed between branches terminated by the cytochrome o-like component, cytochrome a, and cytochrome d. With D-lactate, electrons are transported to cytochrome a, or an unidentified CN(-)-sensitive oxidase, and cytochrome d.
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Affiliation(s)
- U Kalnenieks
- Institute of Microbiology and Biotechnology, University of Latvia, Riga, Latvia
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Kalnenieks U, Galinina N, Toma M, SkÄrds I. Erratum to âelectron transport chain in aerobically cultivated Zymomonas mobilisâ [FEMS microbiol. lett. 143 (1996) 185â189]. FEMS Microbiol Lett 1996. [DOI: 10.1111/j.1574-6968.1996.tb08542.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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