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Smirnova G, Tyulenev A, Sutormina L, Kalashnikova T, Muzyka N, Ushakov V, Samoilova Z, Oktyabrsky O. Regulation of Cysteine Homeostasis and Its Effect on Escherichia coli Sensitivity to Ciprofloxacin in LB Medium. Int J Mol Sci 2024; 25:4424. [PMID: 38674008 PMCID: PMC11050555 DOI: 10.3390/ijms25084424] [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: 03/28/2024] [Revised: 04/15/2024] [Accepted: 04/16/2024] [Indexed: 04/28/2024] Open
Abstract
Cysteine and its derivatives, including H2S, can influence bacterial virulence and sensitivity to antibiotics. In minimal sulfate media, H2S is generated under stress to prevent excess cysteine and, together with incorporation into glutathione and export into the medium, is a mechanism of cysteine homeostasis. Here, we studied the features of cysteine homeostasis in LB medium, where the main source of sulfur is cystine, whose import can create excess cysteine inside cells. We used mutants in the mechanisms of cysteine homeostasis and a set of microbiological and biochemical methods, including the real-time monitoring of sulfide and oxygen, the determination of cysteine and glutathione (GSH), and the expression of the Fur, OxyR, and SOS regulons genes. During normal growth, the parental strain generated H2S when switching respiration to another substrate. The mutations affected the onset time, the intensity and duration of H2S production, cysteine and glutathione levels, bacterial growth and respiration rates, and the induction of defense systems. Exposure to chloramphenicol and high doses of ciprofloxacin increased cysteine content and GSH synthesis. A high inverse relationship between log CFU/mL and bacterial growth rate before ciprofloxacin addition was revealed. The study points to the important role of maintaining cysteine homeostasis during normal growth and antibiotic exposure in LB medium.
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Affiliation(s)
- Galina Smirnova
- Institute of Ecology and Genetics of Microorganisms, Perm Federal Research Center, Russian Academy of Sciences, Goleva 13, 614081 Perm, Russia; (A.T.); (L.S.); (T.K.); (N.M.); (V.U.); (Z.S.); (O.O.)
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2
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Nastasi MR, Borisov VB, Forte E. Membrane-Bound Redox Enzyme Cytochrome bd-I Promotes Carbon Monoxide-Resistant Escherichia coli Growth and Respiration. Int J Mol Sci 2024; 25:1277. [PMID: 38279276 PMCID: PMC10815991 DOI: 10.3390/ijms25021277] [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: 11/16/2023] [Revised: 12/23/2023] [Accepted: 01/18/2024] [Indexed: 01/28/2024] Open
Abstract
The terminal oxidases of bacterial aerobic respiratory chains are redox-active electrogenic enzymes that catalyze the four-electron reduction of O2 to 2H2O taking out electrons from quinol or cytochrome c. Living bacteria often deal with carbon monoxide (CO) which can act as both a signaling molecule and a poison. Bacterial terminal oxidases contain hemes; therefore, they are potential targets for CO. However, our knowledge of this issue is limited and contradictory. Here, we investigated the effect of CO on the cell growth and aerobic respiration of three different Escherichia coli mutants, each expressing only one terminal quinol oxidase: cytochrome bd-I, cytochrome bd-II, or cytochrome bo3. We found that following the addition of CO to bd-I-only cells, a minimal effect on growth was observed, whereas the growth of both bd-II-only and bo3-only strains was severely impaired. Consistently, the degree of resistance of aerobic respiration of bd-I-only cells to CO is high, as opposed to high CO sensitivity displayed by bd-II-only and bo3-only cells consuming O2. Such a difference between the oxidases in sensitivity to CO was also observed with isolated membranes of the mutants. Accordingly, O2 consumption of wild-type cells showed relatively low CO sensitivity under conditions favoring the expression of a bd-type oxidase.
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Affiliation(s)
- Martina R. Nastasi
- Department of Biochemical Sciences, Sapienza University of Rome, 00185 Rome, Italy;
| | - Vitaliy B. Borisov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Elena Forte
- Department of Biochemical Sciences, Sapienza University of Rome, 00185 Rome, Italy;
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3
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Smirnova GV, Tyulenev AV, Bezmaternykh KV, Muzyka NG, Ushakov VY, Oktyabrsky ON. Phosphate starvation is accompanied by disturbance of intracellular cysteine homeostasis in Escherichia coli. Res Microbiol 2023; 174:104108. [PMID: 37516155 DOI: 10.1016/j.resmic.2023.104108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Revised: 07/19/2023] [Accepted: 07/24/2023] [Indexed: 07/31/2023]
Abstract
Metabolic rearrangements that occur during depletion of essential nutrients can lead to accumulation of potentially dangerous metabolites. Here we showed that depletion of phosphate (Pi), accompanied by a sharp inhibition of growth and respiration, caused a transient excess of intracellular cysteine due to a decrease in the rate of protein synthesis. High cysteine level can be dangerous due to its ability to produce ROS and reduce Fe3+ to Fenton-reactive Fe2+. To prevent these negative effects, excess cysteine was mainly incorporated into glutathione (GSH), the intracellular level of which increased by 3 times, and was also exported to the medium and partially degraded to form H2S with participation of 3-mercaptopyruvate sulfotransferase (3MST). The addition of Pi to starving cells led to a sharp recovery of respiration and growth, GSH efflux into the medium and K+ influx into the cells. A pronounced coupling of Pi, GSH, and K+ fluxes was shown upon Pi depletion and addition, which may be necessary to maintain the ionic balance in the cytoplasm. We suggest that processes aimed at restoring cysteine homeostasis may be an integral part of the universal response to stress under different types of stress and for different types of bacteria.
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Affiliation(s)
- Galina V Smirnova
- Institute of Ecology and Genetics of Microorganisms, Perm Federal Research Center, Russian Academy of Sciences, ul. Goleva 13, Perm, 614081, Russia.
| | - Aleksey V Tyulenev
- Institute of Ecology and Genetics of Microorganisms, Perm Federal Research Center, Russian Academy of Sciences, ul. Goleva 13, Perm, 614081, Russia.
| | - Kseniya V Bezmaternykh
- Institute of Ecology and Genetics of Microorganisms, Perm Federal Research Center, Russian Academy of Sciences, ul. Goleva 13, Perm, 614081, Russia.
| | - Nadezda G Muzyka
- Institute of Ecology and Genetics of Microorganisms, Perm Federal Research Center, Russian Academy of Sciences, ul. Goleva 13, Perm, 614081, Russia.
| | - Vadim Y Ushakov
- Institute of Ecology and Genetics of Microorganisms, Perm Federal Research Center, Russian Academy of Sciences, ul. Goleva 13, Perm, 614081, Russia.
| | - Oleg N Oktyabrsky
- Institute of Ecology and Genetics of Microorganisms, Perm Federal Research Center, Russian Academy of Sciences, ul. Goleva 13, Perm, 614081, Russia.
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4
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Nastasi MR, Borisov VB, Forte E. The terminal oxidase cytochrome bd-I confers carbon monoxide resistance to Escherichia coli cells. J Inorg Biochem 2023; 247:112341. [PMID: 37515940 DOI: 10.1016/j.jinorgbio.2023.112341] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Revised: 07/12/2023] [Accepted: 07/22/2023] [Indexed: 07/31/2023]
Abstract
Carbon monoxide (CO) plays a multifaceted role in the physiology of organisms, from poison to signaling molecule. Heme proteins, including terminal oxidases, are plausible CO targets. Three quinol oxidases terminate the branched aerobic respiratory chain of Escherichia coli. These are the heme‑copper cytochrome bo3 and two copper-lacking bd-type cytochromes, bd-I and bd-II. All three enzymes generate a proton motive force during the four-electron oxygen reduction reaction that is used for ATP production. The bd-type oxidases also contribute to mechanisms of bacterial defense against various types of stresses. Here we report that in E. coli cells, at the enzyme concentrations tested, cytochrome bd-I is much more resistant to inhibition by CO than cytochrome bd-II and cytochrome bo3. The apparent half-maximal inhibitory concentration values, IC50, for inhibition of O2 consumption of the membrane-bound bd-II and bo3 oxidases by CO at ~150 μM O2 were estimated to be 187.1 ± 11.1 and 183.3 ± 13.5 μM CO, respectively. Under the same conditions, the maximum inhibition observed with the membrane-bound cytochrome bd-I was 20 ± 10% at ~200 μM CO.
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Affiliation(s)
- Martina R Nastasi
- Department of Biochemical Sciences, Sapienza University of Rome, I-00185 Rome, Italy
| | - Vitaliy B Borisov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia.
| | - Elena Forte
- Department of Biochemical Sciences, Sapienza University of Rome, I-00185 Rome, Italy.
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5
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Ronneau S, Michaux C, Helaine S. Decline in nitrosative stress drives antibiotic persister regrowth during infection. Cell Host Microbe 2023; 31:993-1006.e6. [PMID: 37236190 DOI: 10.1016/j.chom.2023.05.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 04/01/2023] [Accepted: 05/02/2023] [Indexed: 05/28/2023]
Abstract
Internalization of pathogenic bacteria by macrophages results in formation of antibiotic-tolerant persisters. These cells are maintained in a non-growing state for extended periods of time, and it is assumed that their growth resumption causes infection relapse after cessation of antibiotic treatment. Despite this clinical relevance, the signals and conditions that drive persister regrowth during infection are not yet understood. Here, we found that after persister formation in macrophages, host reactive nitrogen species (RNS) produced in response to Salmonella infection lock persisters in growth arrest by intoxicating their TCA cycle, lowering cellular respiration and ATP production. Intracellular persisters resume growth when macrophage RNS production subsides and functionality of their TCA cycle is regained. Persister growth resumption within macrophages is slow and heterogeneous, dramatically extending the time the persister reservoir feeds infection relapse. Using an inhibitor of RNS production, we can force recalcitrant bacteria to regrow during antibiotic treatment, thereby facilitating their eradication.
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Affiliation(s)
- Séverin Ronneau
- Department of Microbiology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115, USA
| | - Charlotte Michaux
- Department of Microbiology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115, USA
| | - Sophie Helaine
- Department of Microbiology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115, USA.
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6
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Smirnova G, Tyulenev A, Muzyka N, Ushakov V, Samoilova Z, Oktyabrsky O. Influence of Growth Medium Composition on Physiological Responses of Escherichia coli to the Action of Chloramphenicol and Ciprofloxacin. BIOTECH 2023; 12:43. [PMID: 37366791 DOI: 10.3390/biotech12020043] [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: 04/11/2023] [Revised: 05/03/2023] [Accepted: 05/23/2023] [Indexed: 06/28/2023] Open
Abstract
The ability of hydrogen sulfide (H2S) to protect bacteria from bactericidal antibiotics has previously been described. The main source of H2S is the desulfurization of cysteine, which is either synthesized by cells from sulfate or transported from the medium, depending on its composition. Applying electrochemical sensors and a complex of biochemical and microbiological methods, changes in growth, respiration, membrane potential, SOS response, H2S production and bacterial survival under the action of bactericidal ciprofloxacin and bacteriostatic chloramphenicol in commonly used media were studied. Chloramphenicol caused a sharp inhibition of metabolism in all studied media. The physiological response of bacteria to ciprofloxacin strongly depended on its dose. In rich LB medium, cells retained metabolic activity at higher concentrations of ciprofloxacin than in minimal M9 medium. This decreased number of surviving cells (CFU) by 2-3 orders of magnitude in LB compared to M9 medium, and shifted optimal bactericidal concentration (OBC) from 0.3 µg/mL in M9 to 3 µg/mL in LB. Both drugs induced transient production of H2S in M9 medium. In media containing cystine, H2S was produced independently of antibiotics. Thus, medium composition significantly modifies physiological response of E. coli to bactericidal antibiotic, which should be taken into account when interpreting data and developing drugs.
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Affiliation(s)
- Galina Smirnova
- Institute of Ecology and Genetics of Microorganisms, Perm Federal Research Center, Russian Academy of Sciences, Goleva 13, 614081 Perm, Russia
| | - Aleksey Tyulenev
- Institute of Ecology and Genetics of Microorganisms, Perm Federal Research Center, Russian Academy of Sciences, Goleva 13, 614081 Perm, Russia
| | - Nadezda Muzyka
- Institute of Ecology and Genetics of Microorganisms, Perm Federal Research Center, Russian Academy of Sciences, Goleva 13, 614081 Perm, Russia
| | - Vadim Ushakov
- Institute of Ecology and Genetics of Microorganisms, Perm Federal Research Center, Russian Academy of Sciences, Goleva 13, 614081 Perm, Russia
| | - Zoya Samoilova
- Institute of Ecology and Genetics of Microorganisms, Perm Federal Research Center, Russian Academy of Sciences, Goleva 13, 614081 Perm, Russia
| | - Oleg Oktyabrsky
- Institute of Ecology and Genetics of Microorganisms, Perm Federal Research Center, Russian Academy of Sciences, Goleva 13, 614081 Perm, Russia
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7
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Makarchuk I, Kägi J, Gerasimova T, Wohlwend D, Friedrich T, Melin F, Hellwig P. pH-dependent kinetics of NO release from E. coli bd-I and bd-II oxidase reveals involvement of Asp/Glu58 B. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2023; 1864:148952. [PMID: 36535430 DOI: 10.1016/j.bbabio.2022.148952] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2022] [Revised: 12/06/2022] [Accepted: 12/09/2022] [Indexed: 12/23/2022]
Abstract
Escherichia coli contains two cytochrome bd oxidases, bd-I and bd-II. The structure of both enzymes is highly similar, but they exhibit subtle differences such as the accessibility of the active site through a putative proton channel. Here, we demonstrate that the duroquinol:dioxygen oxidoreductase activity of bd-I increased with alkaline pH, whereas bd-II showed a broad activity maximum around pH 7. Likewise, the pH dependence of NO release from the reduced active site, an essential property of bd oxidases, differed between the two oxidases as detected by UV/vis spectroscopy. Both findings may be attributed to differences in the proton channel leading to the active site heme d. The channel comprises a titratable residue (Asp58B in bd-I and Glu58B in bd-II). Conservative mutations at this position drastically altered NO release demonstrating its contribution to the process.
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Affiliation(s)
- Iryna Makarchuk
- Laboratoire de Bioélectrochimie et Spectroscopie, UMR 7140, Chimie de la Matière Complexe, Université de Strasbourg-CNRS, 67000 Strasbourg, France
| | - Jan Kägi
- Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr 21, 79104 Freiburg, Germany
| | - Tatjana Gerasimova
- Laboratoire de Bioélectrochimie et Spectroscopie, UMR 7140, Chimie de la Matière Complexe, Université de Strasbourg-CNRS, 67000 Strasbourg, France; Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr 21, 79104 Freiburg, Germany
| | - Daniel Wohlwend
- Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr 21, 79104 Freiburg, Germany
| | - Thorsten Friedrich
- Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr 21, 79104 Freiburg, Germany
| | - Frédéric Melin
- Laboratoire de Bioélectrochimie et Spectroscopie, UMR 7140, Chimie de la Matière Complexe, Université de Strasbourg-CNRS, 67000 Strasbourg, France
| | - Petra Hellwig
- Laboratoire de Bioélectrochimie et Spectroscopie, UMR 7140, Chimie de la Matière Complexe, Université de Strasbourg-CNRS, 67000 Strasbourg, France.
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8
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Goojani HG, Besharati S, Chauhan P, Asseri AH, Lill H, Bald D. Cytochrome bd-I from Escherichia coli is catalytically active in the absence of the CydH subunit. FEBS Lett 2023; 597:547-556. [PMID: 36460943 DOI: 10.1002/1873-3468.14550] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Revised: 10/27/2022] [Accepted: 11/22/2022] [Indexed: 12/04/2022]
Abstract
Cytochrome bd-I from Escherichia coli is a terminal oxidase in the respiratory chain that plays an important role under stress conditions. Cytochrome bd-I was thought to consist of the major subunits CydA and CydB plus the small CydX subunit. Recent high-resolution structures of cytochrome bd-I demonstrated the presence of an additional subunit, CydH/CydY (called CydH here), the function of which is unclear. In this report, we show that in the absence of CydH, cytochrome bd-I is catalytically active, can sustain bacterial growth and displays haem spectra and susceptibility for haem-binding inhibitors comparable to the wild-type enzyme. Removal of CydH did not elicit catalase activity of cytochrome bd-I in our experimental system. Taken together, in the absence of the CydH subunit cytochrome bd-I retained key enzymatic properties.
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Affiliation(s)
- Hojjat Ghasemi Goojani
- Faculty of Science, Amsterdam Institute for Life and Environment (A-LIFE), AIMMS, Vrije Universiteit Amsterdam, The Netherlands
| | - Samira Besharati
- Faculty of Science, Amsterdam Institute for Life and Environment (A-LIFE), AIMMS, Vrije Universiteit Amsterdam, The Netherlands
| | - Priyanka Chauhan
- Faculty of Science, Amsterdam Institute for Life and Environment (A-LIFE), AIMMS, Vrije Universiteit Amsterdam, The Netherlands
| | - Amer H Asseri
- Faculty of Science, Amsterdam Institute for Life and Environment (A-LIFE), AIMMS, Vrije Universiteit Amsterdam, The Netherlands.,Department of Biochemistry, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Holger Lill
- Faculty of Science, Amsterdam Institute for Life and Environment (A-LIFE), AIMMS, Vrije Universiteit Amsterdam, The Netherlands
| | - Dirk Bald
- Faculty of Science, Amsterdam Institute for Life and Environment (A-LIFE), AIMMS, Vrije Universiteit Amsterdam, The Netherlands
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Cysteine Biosynthesis in Campylobacter jejuni: Substrate Specificity of CysM and the Dualism of Sulfide. Biomolecules 2022; 13:biom13010086. [PMID: 36671471 PMCID: PMC9855970 DOI: 10.3390/biom13010086] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 12/28/2022] [Accepted: 12/30/2022] [Indexed: 01/04/2023] Open
Abstract
Campylobacter jejuni is a highly successful enteric pathogen with a small, host-adapted genome (1.64 Mbp, ~1650 coding genes). As a result, C. jejuni has limited capacity in numerous metabolic pathways, including sulfur metabolism. Unable to utilise ionic sulfur, C. jejuni relies on the uptake of exogenous cysteine and its derivatives for its supply of this essential amino acid. Cysteine can also be synthesized de novo by the sole cysteine synthase, CysM. In this study, we explored the substrate specificity of purified C. jejuni CysM and define it as an O-acetyl-L-serine sulfhydrylase with an almost absolute preference for sulfide as sulfur donor. Sulfide is produced in abundance in the intestinal niche C. jejuni colonises, yet sulfide is generally viewed as highly toxic to bacteria. We conducted a series of growth experiments in sulfur-limited media and demonstrate that sulfide is an excellent sulfur source for C. jejuni at physiologically relevant concentrations, combating the view of sulfide as a purely deleterious compound to bacteria. Nonetheless, C. jejuni is indeed inhibited by elevated concentrations of sulfide and we sought to understand the targets involved. Surprisingly, we found that inactivation of the sulfide-sensitive primary terminal oxidase, the cbb3-type cytochrome c oxidase CcoNOPQ, did not explain the majority of growth inhibition by sulfide. Therefore, further work is required to reveal the cellular targets responsible for sulfide toxicity in C. jejuni.
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10
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Han S, Li Y, Gao H. Generation and Physiology of Hydrogen Sulfide and Reactive Sulfur Species in Bacteria. Antioxidants (Basel) 2022; 11:antiox11122487. [PMID: 36552695 PMCID: PMC9774590 DOI: 10.3390/antiox11122487] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 12/14/2022] [Accepted: 12/15/2022] [Indexed: 12/23/2022] Open
Abstract
Sulfur is not only one of the most abundant elements on the Earth, but it is also essential to all living organisms. As life likely began and evolved in a hydrogen sulfide (H2S)-rich environment, sulfur metabolism represents an early form of energy generation via various reactions in prokaryotes and has driven the sulfur biogeochemical cycle since. It has long been known that H2S is toxic to cells at high concentrations, but now this gaseous molecule, at the physiological level, is recognized as a signaling molecule and a regulator of critical biological processes. Recently, many metabolites of H2S, collectively called reactive sulfur species (RSS), have been gradually appreciated as having similar or divergent regulatory roles compared with H2S in living organisms, especially mammals. In prokaryotes, even in bacteria, investigations into generation and physiology of RSS remain preliminary and an understanding of the relevant biological processes is still in its infancy. Despite this, recent and exciting advances in the fields are many. Here, we discuss abiotic and biotic generation of H2S/RSS, sulfur-transforming enzymes and their functioning mechanisms, and their physiological roles as well as the sensing and regulation of H2S/RSS.
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11
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Balasubramanian R, Hori K, Shimizu T, Kasamatsu S, Okamura K, Tanaka K, Ihara H, Masuda S. The Sulfide-Responsive SqrR/BigR Homologous Regulator YgaV of Escherichia coli Controls Expression of Anaerobic Respiratory Genes and Antibiotic Tolerance. Antioxidants (Basel) 2022; 11:antiox11122359. [PMID: 36552568 PMCID: PMC9774250 DOI: 10.3390/antiox11122359] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Revised: 11/22/2022] [Accepted: 11/24/2022] [Indexed: 11/30/2022] Open
Abstract
Compositions and activities of bacterial flora in the gastrointestinal tract significantly influence the metabolism, health, and disease of host humans and animals. These enteric bacteria can switch between aerobic and anaerobic growth if oxygen tension becomes limited. Interestingly, the switching mechanism is important for preventing reactive oxygen species (ROS) production and antibiotic tolerance. Studies have also shown that intracellular and extracellular sulfide molecules are involved in this switching control, although the mechanism is not fully clarified. Here, we found that YgaV, a sulfide-responsive transcription factor SqrR/BigR homolog, responded to sulfide compounds in vivo and in vitro to control anaerobic respiratory gene expression. YgaV also responded to H2O2 scavenging in the enteric bacterium Escherichia coli. Although the wild-type (WT) showed increased antibiotic tolerance under H2S-atmospheric conditions, the ygaV mutant did not show such a phenotype. Additionally, antibiotic sensitivity was higher in the mutant than in the WT of both types in the presence and absence of exogenous H2S. These results, therefore, indicated that YgaV-dependent transcriptional regulation was responsible for maintaining redox homeostasis, ROS scavenging, and antibiotic tolerance.
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Affiliation(s)
| | - Koichi Hori
- Department of Life Science and Technology, Tokyo Institute of Technology, Yokohama 226-8501, Japan
| | - Takayuki Shimizu
- Graduate School of Arts and Sciences, The University of Tokyo, Tokyo 153-8902, Japan
| | - Shingo Kasamatsu
- Department of Biological Chemistry, Graduate School of Science, Osaka Metropolitan University, Osaka 599-8531, Japan
| | - Kae Okamura
- Department of Biological Chemistry, Graduate School of Science, Osaka Metropolitan University, Osaka 599-8531, Japan
| | - Kan Tanaka
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama 226-8501, Japan
| | - Hideshi Ihara
- Department of Biological Chemistry, Graduate School of Science, Osaka Metropolitan University, Osaka 599-8531, Japan
| | - Shinji Masuda
- Department of Life Science and Technology, Tokyo Institute of Technology, Yokohama 226-8501, Japan
- Correspondence:
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12
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Pei S, Liu P, Parker DA, Mackie RI, Rao CV. Systems analysis of the effect of hydrogen sulfide on the growth of Methylococcus capsulatus Bath. Appl Microbiol Biotechnol 2022; 106:7879-7890. [DOI: 10.1007/s00253-022-12236-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Revised: 10/04/2022] [Accepted: 10/07/2022] [Indexed: 11/02/2022]
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13
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Walsh BJC, Costa SS, Edmonds KA, Trinidad JC, Issoglio FM, Brito JA, Giedroc DP. Metabolic and Structural Insights into Hydrogen Sulfide Mis-Regulation in Enterococcus faecalis. Antioxidants (Basel) 2022; 11:1607. [PMID: 36009332 PMCID: PMC9405070 DOI: 10.3390/antiox11081607] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2022] [Revised: 08/11/2022] [Accepted: 08/17/2022] [Indexed: 11/16/2022] Open
Abstract
Hydrogen sulfide (H2S) is implicated as a cytoprotective agent that bacteria employ in response to host-induced stressors, such as oxidative stress and antibiotics. The physiological benefits often attributed to H2S, however, are likely a result of downstream, more oxidized forms of sulfur, collectively termed reactive sulfur species (RSS) and including the organic persulfide (RSSH). Here, we investigated the metabolic response of the commensal gut microorganism Enterococcus faecalis to exogenous Na2S as a proxy for H2S/RSS toxicity. We found that exogenous sulfide increases protein abundance for enzymes responsible for the biosynthesis of coenzyme A (CoA). Proteome S-sulfuration (persulfidation), a posttranslational modification implicated in H2S signal transduction, is also widespread in this organism and is significantly elevated by exogenous sulfide in CstR, the RSS sensor, coenzyme A persulfide (CoASSH) reductase (CoAPR) and enzymes associated with de novo fatty acid biosynthesis and acetyl-CoA synthesis. Exogenous sulfide significantly impacts the speciation of fatty acids as well as cellular concentrations of acetyl-CoA, suggesting that protein persulfidation may impact flux through these pathways. Indeed, CoASSH is an inhibitor of E. faecalis phosphotransacetylase (Pta), suggesting that an important metabolic consequence of increased levels of H2S/RSS may be over-persulfidation of this key metabolite, which, in turn, inhibits CoA and acyl-CoA-utilizing enzymes. Our 2.05 Å crystallographic structure of CoA-bound CoAPR provides new structural insights into CoASSH clearance in E. faecalis.
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Affiliation(s)
- Brenna J. C. Walsh
- Department of Chemistry, Indiana University, Bloomington, IN 47405-7102, USA
| | - Sofia Soares Costa
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, 2780-157 Oeiras, Portugal
| | | | | | - Federico M. Issoglio
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, 2780-157 Oeiras, Portugal
- Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN)-CONICET and Departamento de Química Biológica, Universidad de Buenos Aires, Buenos Aires C1428EHA, Argentina
| | - José A. Brito
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, 2780-157 Oeiras, Portugal
| | - David P. Giedroc
- Department of Chemistry, Indiana University, Bloomington, IN 47405-7102, USA
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN 47405-7003, USA
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14
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Forte E, Nastasi MR, Borisov VB. Preparations of Terminal Oxidase Cytochrome bd-II Isolated from Escherichia coli Reveal Significant Hydrogen Peroxide Scavenging Activity. BIOCHEMISTRY. BIOKHIMIIA 2022; 87:720-730. [PMID: 36171653 DOI: 10.1134/s0006297922080041] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 04/29/2022] [Accepted: 04/29/2022] [Indexed: 06/16/2023]
Abstract
Cytochrome bd-II is one of the three terminal quinol oxidases of the aerobic respiratory chain of Escherichia coli. Preparations of the detergent-solubilized untagged bd-II oxidase isolated from the bacterium were shown to scavenge hydrogen peroxide (H2O2) with high rate producing molecular oxygen (O2). Addition of H2O2 to the same buffer that does not contain enzyme or contains thermally denatured cytochrome bd-II does not lead to any O2 production. The latter observation rules out involvement of adventitious transition metals bound to the protein. The H2O2-induced O2 production is not susceptible to inhibition by N-ethylmaleimide (the sulfhydryl binding compound), antimycin A (the compound that binds specifically to a quinol binding site), and CO (diatomic gas that binds specifically to the reduced heme d). However, O2 formation is inhibited by cyanide (IC50 = 4.5 ± 0.5 µM) and azide. Addition of H2O2 in the presence of dithiothreitol and ubiquinone-1 does not inactivate cytochrome bd-II and apparently does not affect the O2 reductase activity of the enzyme. The ability of cytochrome bd-II to detoxify H2O2 could play a role in bacterial physiology by conferring resistance to the peroxide-mediated stress.
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Affiliation(s)
- Elena Forte
- Department of Biochemical Sciences, Sapienza University of Rome, Rome, I-00185, Italy
| | - Martina R Nastasi
- Department of Biochemical Sciences, Sapienza University of Rome, Rome, I-00185, Italy
| | - Vitaliy B Borisov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia.
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15
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Bioenergetics and Reactive Nitrogen Species in Bacteria. Int J Mol Sci 2022; 23:ijms23137321. [PMID: 35806323 PMCID: PMC9266656 DOI: 10.3390/ijms23137321] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 06/27/2022] [Accepted: 06/28/2022] [Indexed: 11/24/2022] Open
Abstract
The production of reactive nitrogen species (RNS) by the innate immune system is part of the host’s defense against invading pathogenic bacteria. In this review, we summarize recent studies on the molecular basis of the effects of nitric oxide and peroxynitrite on microbial respiration and energy conservation. We discuss possible molecular mechanisms underlying RNS resistance in bacteria mediated by unique respiratory oxygen reductases, the mycobacterial bcc-aa3 supercomplex, and bd-type cytochromes. A complete picture of the impact of RNS on microbial bioenergetics is not yet available. However, this research area is developing very rapidly, and the knowledge gained should help us develop new methods of treating infectious diseases.
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16
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Wang T, Yang Y, Liu M, Liu H, Liu H, Xia Y, Xun L. Elemental Sulfur Inhibits Yeast Growth via Producing Toxic Sulfide and Causing Disulfide Stress. Antioxidants (Basel) 2022; 11:antiox11030576. [PMID: 35326226 PMCID: PMC8945482 DOI: 10.3390/antiox11030576] [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: 02/13/2022] [Revised: 03/14/2022] [Accepted: 03/15/2022] [Indexed: 11/16/2022] Open
Abstract
Elemental sulfur is a common fungicide, but its inhibition mechanism is unclear. Here, we investigated the effects of elemental sulfur on the single-celled fungus Saccharomyces cerevisiae and showed that the inhibition was due to its function as a strong oxidant. It rapidly entered S. cerevisiae. Inside the cytoplasm, it reacted with glutathione to generate glutathione persulfide that then reacted with another glutathione to produce H2S and glutathione disulfide. H2S reversibly inhibited the oxygen consumption by the mitochondrial electron transport chain, and the accumulation of glutathione disulfide caused disulfide stress and increased reactive oxygen species in S. cerevisiae. Elemental sulfur inhibited the growth of S. cerevisiae; however, it did not kill the yeast for up to 2 h exposure. The combined action of elemental sulfur and hosts’ immune responses may lead to the demise of fungal pathogens.
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Affiliation(s)
- Tianqi Wang
- State Key Laboratory of Microbial Technology, Shandong University, 72 Binhai Road, Qingdao 266237, China; (T.W.); (Y.Y.); (M.L.); (H.L.); (H.L.)
| | - Yuqing Yang
- State Key Laboratory of Microbial Technology, Shandong University, 72 Binhai Road, Qingdao 266237, China; (T.W.); (Y.Y.); (M.L.); (H.L.); (H.L.)
| | - Menghui Liu
- State Key Laboratory of Microbial Technology, Shandong University, 72 Binhai Road, Qingdao 266237, China; (T.W.); (Y.Y.); (M.L.); (H.L.); (H.L.)
| | - Honglei Liu
- State Key Laboratory of Microbial Technology, Shandong University, 72 Binhai Road, Qingdao 266237, China; (T.W.); (Y.Y.); (M.L.); (H.L.); (H.L.)
| | - Huaiwei Liu
- State Key Laboratory of Microbial Technology, Shandong University, 72 Binhai Road, Qingdao 266237, China; (T.W.); (Y.Y.); (M.L.); (H.L.); (H.L.)
| | - Yongzhen Xia
- State Key Laboratory of Microbial Technology, Shandong University, 72 Binhai Road, Qingdao 266237, China; (T.W.); (Y.Y.); (M.L.); (H.L.); (H.L.)
- Correspondence: (Y.X.); (L.X.); Tel.: +86-532-58631572 (Y.X.); +1-509-335-2787 (L.X.)
| | - Luying Xun
- State Key Laboratory of Microbial Technology, Shandong University, 72 Binhai Road, Qingdao 266237, China; (T.W.); (Y.Y.); (M.L.); (H.L.); (H.L.)
- School of Molecular Biosciences, Washington State University, Pullman, WA 991647520, USA
- Correspondence: (Y.X.); (L.X.); Tel.: +86-532-58631572 (Y.X.); +1-509-335-2787 (L.X.)
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17
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Friedrich T, Wohlwend D, Borisov VB. Recent Advances in Structural Studies of Cytochrome bd and Its Potential Application as a Drug Target. Int J Mol Sci 2022; 23:ijms23063166. [PMID: 35328590 PMCID: PMC8951039 DOI: 10.3390/ijms23063166] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 03/14/2022] [Accepted: 03/14/2022] [Indexed: 02/06/2023] Open
Abstract
Cytochrome bd is a triheme copper-free terminal oxidase in membrane respiratory chains of prokaryotes. This unique molecular machine couples electron transfer from quinol to O2 with the generation of a proton motive force without proton pumping. Apart from energy conservation, the bd enzyme plays an additional key role in the microbial cell, being involved in the response to different environmental stressors. Cytochrome bd promotes virulence in a number of pathogenic species that makes it a suitable molecular drug target candidate. This review focuses on recent advances in understanding the structure of cytochrome bd and the development of its selective inhibitors.
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Affiliation(s)
- Thorsten Friedrich
- Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, D-79104 Freiburg, Germany; (T.F.); (D.W.)
| | - Daniel Wohlwend
- Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, D-79104 Freiburg, Germany; (T.F.); (D.W.)
| | - Vitaliy B. Borisov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, 119991 Moscow, Russia
- Correspondence:
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18
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Chen J, Xie P, Huang Y, Gao H. Complex Interplay of Heme-Copper Oxidases with Nitrite and Nitric Oxide. Int J Mol Sci 2022; 23:979. [PMID: 35055165 PMCID: PMC8780969 DOI: 10.3390/ijms23020979] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 01/13/2022] [Accepted: 01/15/2022] [Indexed: 12/19/2022] Open
Abstract
Nitrite and nitric oxide (NO), two active and critical nitrogen oxides linking nitrate to dinitrogen gas in the broad nitrogen biogeochemical cycle, are capable of interacting with redox-sensitive proteins. The interactions of both with heme-copper oxidases (HCOs) serve as the foundation not only for the enzymatic interconversion of nitrogen oxides but also for the inhibitory activity. From extensive studies, we now know that NO interacts with HCOs in a rapid and reversible manner, either competing with oxygen or not. During interconversion, a partially reduced heme/copper center reduces the nitrite ion, producing NO with the heme serving as the reductant and the cupric ion providing a Lewis acid interaction with nitrite. The interaction may lead to the formation of either a relatively stable nitrosyl-derivative of the enzyme reduced or a more labile nitrite-derivative of the enzyme oxidized through two different pathways, resulting in enzyme inhibition. Although nitrite and NO show similar biochemical properties, a growing body of evidence suggests that they are largely treated as distinct molecules by bacterial cells. NO seemingly interacts with all hemoproteins indiscriminately, whereas nitrite shows high specificity to HCOs. Moreover, as biologically active molecules and signal molecules, nitrite and NO directly affect the activity of different enzymes and are perceived by completely different sensing systems, respectively, through which they are linked to different biological processes. Further attempts to reconcile this apparent contradiction could open up possible avenues for the application of these nitrogen oxides in a variety of fields, the pharmaceutical industry in particular.
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Affiliation(s)
| | | | | | - Haichun Gao
- Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou 310058, China; (J.C.); (P.X.); (Y.H.)
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19
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Borisov VB, Forte E. Impact of Hydrogen Sulfide on Mitochondrial and Bacterial Bioenergetics. Int J Mol Sci 2021; 22:12688. [PMID: 34884491 PMCID: PMC8657789 DOI: 10.3390/ijms222312688] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Revised: 11/20/2021] [Accepted: 11/22/2021] [Indexed: 02/06/2023] Open
Abstract
This review focuses on the effects of hydrogen sulfide (H2S) on the unique bioenergetic molecular machines in mitochondria and bacteria-the protein complexes of electron transport chains and associated enzymes. H2S, along with nitric oxide and carbon monoxide, belongs to the class of endogenous gaseous signaling molecules. This compound plays critical roles in physiology and pathophysiology. Enzymes implicated in H2S metabolism and physiological actions are promising targets for novel pharmaceutical agents. The biological effects of H2S are biphasic, changing from cytoprotection to cytotoxicity through increasing the compound concentration. In mammals, H2S enhances the activity of FoF1-ATP (adenosine triphosphate) synthase and lactate dehydrogenase via their S-sulfhydration, thereby stimulating mitochondrial electron transport. H2S serves as an electron donor for the mitochondrial respiratory chain via sulfide quinone oxidoreductase and cytochrome c oxidase at low H2S levels. The latter enzyme is inhibited by high H2S concentrations, resulting in the reversible inhibition of electron transport and ATP production in mitochondria. In the branched respiratory chain of Escherichia coli, H2S inhibits the bo3 terminal oxidase but does not affect the alternative bd-type oxidases. Thus, in E. coli and presumably other bacteria, cytochrome bd permits respiration and cell growth in H2S-rich environments. A complete picture of the impact of H2S on bioenergetics is lacking, but this field is fast-moving, and active ongoing research on this topic will likely shed light on additional, yet unknown biological effects.
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Affiliation(s)
- Vitaliy B. Borisov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, 119991 Moscow, Russia
| | - Elena Forte
- Department of Biochemical Sciences, Sapienza University of Rome, 00185 Rome, Italy;
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20
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Siletsky SA, Borisov VB. Proton Pumping and Non-Pumping Terminal Respiratory Oxidases: Active Sites Intermediates of These Molecular Machines and Their Derivatives. Int J Mol Sci 2021; 22:10852. [PMID: 34639193 PMCID: PMC8509429 DOI: 10.3390/ijms221910852] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 10/04/2021] [Accepted: 10/05/2021] [Indexed: 11/16/2022] Open
Abstract
Terminal respiratory oxidases are highly efficient molecular machines. These most important bioenergetic membrane enzymes transform the energy of chemical bonds released during the transfer of electrons along the respiratory chains of eukaryotes and prokaryotes from cytochromes or quinols to molecular oxygen into a transmembrane proton gradient. They participate in regulatory cascades and physiological anti-stress reactions in multicellular organisms. They also allow microorganisms to adapt to low-oxygen conditions, survive in chemically aggressive environments and acquire antibiotic resistance. To date, three-dimensional structures with atomic resolution of members of all major groups of terminal respiratory oxidases, heme-copper oxidases, and bd-type cytochromes, have been obtained. These groups of enzymes have different origins and a wide range of functional significance in cells. At the same time, all of them are united by a catalytic reaction of four-electron reduction in oxygen into water which proceeds without the formation and release of potentially dangerous ROS from active sites. The review analyzes recent structural and functional studies of oxygen reduction intermediates in the active sites of terminal respiratory oxidases, the features of catalytic cycles, and the properties of the active sites of these enzymes.
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Affiliation(s)
- Sergey A. Siletsky
- Department of Bioenergetics, Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, Moscow 119991, Russia
| | - Vitaliy B. Borisov
- Department of Molecular Energetics of Microorganisms, Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, Moscow 119991, Russia;
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21
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Structure and function of aerotolerant, multiple-turnover THI4 thiazole synthases. Biochem J 2021; 478:3265-3279. [PMID: 34409984 PMCID: PMC8454699 DOI: 10.1042/bcj20210565] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 08/18/2021] [Accepted: 08/19/2021] [Indexed: 12/29/2022]
Abstract
Plant and fungal THI4 thiazole synthases produce the thiamin thiazole moiety in aerobic conditions via a single-turnover suicide reaction that uses an active-site Cys residue as sulfur donor. Multiple-turnover (i.e. catalytic) THI4s lacking an active-site Cys (non-Cys THI4s) that use sulfide as sulfur donor have been biochemically characterized —– but only from archaeal methanogens that are anaerobic, O2-sensitive hyperthermophiles from sulfide-rich habitats. These THI4s prefer iron as cofactor. A survey of prokaryote genomes uncovered non-Cys THI4s in aerobic mesophiles from sulfide-poor habitats, suggesting that multiple-turnover THI4 operation is possible in aerobic, mild, low-sulfide conditions. This was confirmed by testing 23 representative non-Cys THI4s for complementation of an Escherichia coli ΔthiG thiazole auxotroph in aerobic conditions. Sixteen were clearly active, and more so when intracellular sulfide level was raised by supplying Cys, demonstrating catalytic function in the presence of O2 at mild temperatures and indicating use of sulfide or a sulfide metabolite as sulfur donor. Comparative genomic evidence linked non-Cys THI4s with proteins from families that bind, transport, or metabolize cobalt or other heavy metals. The crystal structure of the aerotolerant bacterial Thermovibrio ammonificans THI4 was determined to probe the molecular basis of aerotolerance. The structure suggested no large deviations compared with the structures of THI4s from O2-sensitive methanogens, but is consistent with an alternative catalytic metal. Together with complementation data, use of cobalt rather than iron was supported. We conclude that catalytic THI4s can indeed operate aerobically and that the metal cofactor inserted is a likely natural determinant of aerotolerance.
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22
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Kunota TTR, Rahman MA, Truebody BE, Mackenzie JS, Saini V, Lamprecht DA, Adamson JH, Sevalkar RR, Lancaster JR, Berney M, Glasgow JN, Steyn AJC. Mycobacterium tuberculosis H 2S Functions as a Sink to Modulate Central Metabolism, Bioenergetics, and Drug Susceptibility. Antioxidants (Basel) 2021; 10:1285. [PMID: 34439535 PMCID: PMC8389258 DOI: 10.3390/antiox10081285] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Revised: 08/04/2021] [Accepted: 08/07/2021] [Indexed: 02/03/2023] Open
Abstract
H2S is a potent gasotransmitter in eukaryotes and bacteria. Host-derived H2S has been shown to profoundly alter M. tuberculosis (Mtb) energy metabolism and growth. However, compelling evidence for endogenous production of H2S and its role in Mtb physiology is lacking. We show that multidrug-resistant and drug-susceptible clinical Mtb strains produce H2S, whereas H2S production in non-pathogenic M. smegmatis is barely detectable. We identified Rv3684 (Cds1) as an H2S-producing enzyme in Mtb and show that cds1 disruption reduces, but does not eliminate, H2S production, suggesting the involvement of multiple genes in H2S production. We identified endogenous H2S to be an effector molecule that maintains bioenergetic homeostasis by stimulating respiration primarily via cytochrome bd. Importantly, H2S plays a key role in central metabolism by modulating the balance between oxidative phosphorylation and glycolysis, and it functions as a sink to recycle sulfur atoms back to cysteine to maintain sulfur homeostasis. Lastly, Mtb-generated H2S regulates redox homeostasis and susceptibility to anti-TB drugs clofazimine and rifampicin. These findings reveal previously unknown facets of Mtb physiology and have implications for routine laboratory culturing, understanding drug susceptibility, and improved diagnostics.
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Affiliation(s)
- Tafara T. R. Kunota
- Africa Health Research Institute, University of KwaZulu Natal, Durban 4001, South Africa; (T.T.R.K.); (M.A.R.); (B.E.T.); (J.S.M.); (D.A.L.); (J.H.A.)
| | - Md. Aejazur Rahman
- Africa Health Research Institute, University of KwaZulu Natal, Durban 4001, South Africa; (T.T.R.K.); (M.A.R.); (B.E.T.); (J.S.M.); (D.A.L.); (J.H.A.)
| | - Barry E. Truebody
- Africa Health Research Institute, University of KwaZulu Natal, Durban 4001, South Africa; (T.T.R.K.); (M.A.R.); (B.E.T.); (J.S.M.); (D.A.L.); (J.H.A.)
| | - Jared S. Mackenzie
- Africa Health Research Institute, University of KwaZulu Natal, Durban 4001, South Africa; (T.T.R.K.); (M.A.R.); (B.E.T.); (J.S.M.); (D.A.L.); (J.H.A.)
| | - Vikram Saini
- Department of Biotechnology, All India Institute of Medical Sciences, New Delhi 110029, India;
| | - Dirk A. Lamprecht
- Africa Health Research Institute, University of KwaZulu Natal, Durban 4001, South Africa; (T.T.R.K.); (M.A.R.); (B.E.T.); (J.S.M.); (D.A.L.); (J.H.A.)
| | - John H. Adamson
- Africa Health Research Institute, University of KwaZulu Natal, Durban 4001, South Africa; (T.T.R.K.); (M.A.R.); (B.E.T.); (J.S.M.); (D.A.L.); (J.H.A.)
| | - Ritesh R. Sevalkar
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA; (R.R.S.); (J.N.G.)
| | - Jack R. Lancaster
- Department of Pharmacology and Chemical Biology, Vascular Medicine Institute, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA;
| | - Michael Berney
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, New York, NY 10462, USA;
| | - Joel N. Glasgow
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA; (R.R.S.); (J.N.G.)
| | - Adrie J. C. Steyn
- Africa Health Research Institute, University of KwaZulu Natal, Durban 4001, South Africa; (T.T.R.K.); (M.A.R.); (B.E.T.); (J.S.M.); (D.A.L.); (J.H.A.)
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA; (R.R.S.); (J.N.G.)
- Centers for AIDS Research and Free Radical Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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23
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Counts JA, Willard DJ, Kelly RM. Life in hot acid: a genome-based reassessment of the archaeal order Sulfolobales. Environ Microbiol 2021; 23:3568-3584. [PMID: 32776389 PMCID: PMC10560490 DOI: 10.1111/1462-2920.15189] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Revised: 07/31/2020] [Accepted: 08/06/2020] [Indexed: 01/07/2023]
Abstract
The order Sulfolobales was one of the first named Archaeal lineages, with globally distributed members from terrestrial thermal acid springs (pH < 4; T > 65°C). The Sulfolobales represent broad metabolic capabilities, ranging from lithotrophy, based on inorganic iron and sulfur biotransformations, to autotrophy, to chemoheterotrophy in less acidophilic species. Components of the 3-hydroxypropionate/4-hydroxybutyrate carbon fixation cycle, as well as sulfur oxidation, are nearly universally conserved, although dissimilatory sulfur reduction and disproportionation (Acidianus, Stygiolobus and Sulfurisphaera) and iron oxidation (Acidianus, Metallosphaera, Sulfurisphaera, Sulfuracidifex and Sulfodiicoccus) are limited to fewer lineages. Lithotrophic marker genes appear more often in highly acidophilic lineages. Despite the presence of facultative anaerobes and one confirmed obligate anaerobe, oxidase complexes (fox, sox, dox and a new putative cytochrome bd) are prevalent in many species (even facultative/obligate anaerobes), suggesting a key role for oxygen among the Sulfolobales. The presence of fox genes tracks with a putative antioxidant OsmC family peroxiredoxin, an indicator of oxidative stress derived from mixing reactive metals and oxygen. Extreme acidophily appears to track inversely with heterotrophy but directly with lithotrophy. Recent phylogenetic re-organization efforts are supported by the comparative genomics here, although several changes are proposed, including the expansion of the genus Saccharolobus.
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Affiliation(s)
- James A. Counts
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695 USA
| | - Daniel J. Willard
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695 USA
| | - Robert M. Kelly
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695 USA
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24
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Garg N, Taylor AJ, Pastorelli F, Flannery SE, Jackson PJ, Johnson MP, Kelly DJ. Genes Linking Copper Trafficking and Homeostasis to the Biogenesis and Activity of the cbb 3-Type Cytochrome c Oxidase in the Enteric Pathogen Campylobacter jejuni. Front Microbiol 2021; 12:683260. [PMID: 34248902 PMCID: PMC8267372 DOI: 10.3389/fmicb.2021.683260] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2021] [Accepted: 05/26/2021] [Indexed: 11/13/2022] Open
Abstract
Bacterial C-type haem-copper oxidases in the cbb 3 family are widespread in microaerophiles, which exploit their high oxygen-binding affinity for growth in microoxic niches. In microaerophilic pathogens, C-type oxidases can be essential for infection, yet little is known about their biogenesis compared to model bacteria. Here, we have identified genes involved in cbb 3-oxidase (Cco) assembly and activity in the Gram-negative pathogen Campylobacter jejuni, the commonest cause of human food-borne bacterial gastroenteritis. Several genes of unknown function downstream of the oxidase structural genes ccoNOQP were shown to be essential (cj1483c and cj1486c) or important (cj1484c and cj1485c) for Cco activity; Cj1483 is a CcoH homologue, but Cj1484 (designated CcoZ) has structural similarity to MSMEG_4692, involved in Qcr-oxidase supercomplex formation in Mycobacterium smegmatis. Blue-native polyacrylamide gel electrophoresis of detergent solubilised membranes revealed three major bands, one of which contained CcoZ along with Qcr and oxidase subunits. Deletion of putative copper trafficking genes ccoI (cj1155c) and ccoS (cj1154c) abolished Cco activity, which was partially restored by addition of copper during growth, while inactivation of cj0369c encoding a CcoG homologue led to a partial reduction in Cco activity. Deletion of an operon encoding PCu A C (Cj0909) and Sco (Cj0911) periplasmic copper chaperone homologues reduced Cco activity, which was partially restored in the cj0911 mutant by exogenous copper. Phenotypic analyses of gene deletions in the cj1161c-1166c cluster, encoding several genes involved in intracellular metal homeostasis, showed that inactivation of copA (cj1161c), or copZ (cj1162c) led to both elevated intracellular Cu and reduced Cco activity, effects exacerbated at high external Cu. Our work has therefore identified (i) additional Cco subunits, (ii) a previously uncharacterized set of genes linking copper trafficking and Cco activity, and (iii) connections with Cu homeostasis in this important pathogen.
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Affiliation(s)
- Nitanshu Garg
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, United Kingdom
| | - Aidan J Taylor
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, United Kingdom
| | - Federica Pastorelli
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, United Kingdom
| | - Sarah E Flannery
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, United Kingdom
| | - Phillip J Jackson
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, United Kingdom
| | - Matthew P Johnson
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, United Kingdom
| | - David J Kelly
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, United Kingdom
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25
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Walker A, Schmitt-Kopplin P. The role of fecal sulfur metabolome in inflammatory bowel diseases. Int J Med Microbiol 2021; 311:151513. [PMID: 34147944 DOI: 10.1016/j.ijmm.2021.151513] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 04/22/2021] [Accepted: 05/17/2021] [Indexed: 12/17/2022] Open
Abstract
Sulfur metabolism and sulfur-containing metabolites play an important role in the human digestive system, and sulfur compounds and pathways are associated with inflammatory bowel diseases (IBD). In fact, cysteine metabolism results in the production of taurine and sulfate, and gut microbes catabolize them into hydrogen sulfide, a signaling molecule with various biological functions. Besides metabolites originating from sulfur metabolism, several other sulfur-containing metabolites of different classes were detected in human feces, consisting of non-volatile and volatile compounds. Sulfated steroids and bile acids such as taurine-conjugated bile acids are the major classes along with sulfur amino acids and sulfur-containing peptides. Indeed, sulfur-containing metabolites were described in stool samples from healthy subjects, patients suffering from colorectal cancer or IBD. In metabolomics-driven studies, around 50 known sulfur-containing metabolites were linked to IBD. Taurine, taurocholic acid, taurochenodeoxycholic acid, methionine, methanethiol and hydrogen sulfide were regularly reported in IBD studies, and most of them were elevated in stool samples from IBD patients. We summarized from this review that there is strong interplay between perturbed gut microbiota in IBD, and the consistently higher abundance of sulfur-containing metabolites, which potentially represent substrates for sulfidogenic bacteria such as Bilophila or Escherichia and promote their growth. These bacteria might shift their metabolism towards the degradation of taurine and cysteine and therefore to a higher hydrogen sulfide production.
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Affiliation(s)
- Alesia Walker
- Research Unit Analytical BioGeoChemistry, Helmholtz Zentrum München, Neuherberg, Germany.
| | - Philippe Schmitt-Kopplin
- Research Unit Analytical BioGeoChemistry, Helmholtz Zentrum München, Neuherberg, Germany; ZIEL Institute for Food and Health, Technical University of Munich, Freising, Germany; Chair of Analytical Food Chemistry, Technical University of Munich, Freising, Germany
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Identification and optimization of quinolone-based inhibitors against cytochrome bd oxidase using an electrochemical assay. Electrochim Acta 2021. [DOI: 10.1016/j.electacta.2021.138293] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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Borisov VB, Siletsky SA, Paiardini A, Hoogewijs D, Forte E, Giuffrè A, Poole RK. Bacterial Oxidases of the Cytochrome bd Family: Redox Enzymes of Unique Structure, Function, and Utility As Drug Targets. Antioxid Redox Signal 2021; 34:1280-1318. [PMID: 32924537 PMCID: PMC8112716 DOI: 10.1089/ars.2020.8039] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 09/01/2020] [Accepted: 09/02/2020] [Indexed: 12/23/2022]
Abstract
Significance: Cytochrome bd is a ubiquinol:oxygen oxidoreductase of many prokaryotic respiratory chains with a unique structure and functional characteristics. Its primary role is to couple the reduction of molecular oxygen, even at submicromolar concentrations, to water with the generation of a proton motive force used for adenosine triphosphate production. Cytochrome bd is found in many bacterial pathogens and, surprisingly, in bacteria formally denoted as anaerobes. It endows bacteria with resistance to various stressors and is a potential drug target. Recent Advances: We summarize recent advances in the biochemistry, structure, and physiological functions of cytochrome bd in the light of exciting new three-dimensional structures of the oxidase. The newly discovered roles of cytochrome bd in contributing to bacterial protection against hydrogen peroxide, nitric oxide, peroxynitrite, and hydrogen sulfide are assessed. Critical Issues: Fundamental questions remain regarding the precise delineation of electron flow within this multihaem oxidase and how the extraordinarily high affinity for oxygen is accomplished, while endowing bacteria with resistance to other small ligands. Future Directions: It is clear that cytochrome bd is unique in its ability to confer resistance to toxic small molecules, a property that is significant for understanding the propensity of pathogens to possess this oxidase. Since cytochrome bd is a uniquely bacterial enzyme, future research should focus on harnessing fundamental knowledge of its structure and function to the development of novel and effective antibacterial agents.
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Affiliation(s)
- Vitaliy B. Borisov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russian Federation
| | - Sergey A. Siletsky
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russian Federation
| | | | - David Hoogewijs
- Department of Medicine/Physiology, University of Fribourg, Fribourg, Switzerland
| | - Elena Forte
- Department of Biochemical Sciences, Sapienza University of Rome, Rome, Italy
| | | | - Robert K. Poole
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, United Kingdom
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Borisov VB, Siletsky SA, Nastasi MR, Forte E. ROS Defense Systems and Terminal Oxidases in Bacteria. Antioxidants (Basel) 2021; 10:antiox10060839. [PMID: 34073980 PMCID: PMC8225038 DOI: 10.3390/antiox10060839] [Citation(s) in RCA: 55] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Revised: 05/19/2021] [Accepted: 05/21/2021] [Indexed: 02/07/2023] Open
Abstract
Reactive oxygen species (ROS) comprise the superoxide anion (O2•−), hydrogen peroxide (H2O2), hydroxyl radical (•OH), and singlet oxygen (1O2). ROS can damage a variety of macromolecules, including DNA, RNA, proteins, and lipids, and compromise cell viability. To prevent or reduce ROS-induced oxidative stress, bacteria utilize different ROS defense mechanisms, of which ROS scavenging enzymes, such as superoxide dismutases, catalases, and peroxidases, are the best characterized. Recently, evidence has been accumulating that some of the terminal oxidases in bacterial respiratory chains may also play a protective role against ROS. The present review covers this role of terminal oxidases in light of recent findings.
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Affiliation(s)
- Vitaliy B. Borisov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, 119991 Moscow, Russia;
- Correspondence: (V.B.B.); (E.F.)
| | - Sergey A. Siletsky
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, 119991 Moscow, Russia;
| | - Martina R. Nastasi
- Department of Biochemical Sciences, Sapienza University of Rome, Piazzale Aldo Moro, 5, 00185 Rome, Italy;
| | - Elena Forte
- Department of Biochemical Sciences, Sapienza University of Rome, Piazzale Aldo Moro, 5, 00185 Rome, Italy;
- Correspondence: (V.B.B.); (E.F.)
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Abstract
Carbon monoxide has an infamous reputation as a toxic gas, and it has been suggested that it has potential as an antibacterial agent. Despite this, how bacteria resist its toxic effects is not well understood. Carbon monoxide (CO) gas is infamous for its acute toxicity. This toxicity predominantly stems from its tendency to form carbonyl complexes with transition metals, thus inhibiting the heme-prosthetic groups of proteins, including respiratory terminal oxidases. While CO has been proposed as an antibacterial agent, the evidence supporting its toxicity toward bacteria is equivocal, and its cellular targets remain poorly defined. In this work, we investigate the physiological response of mycobacteria to CO. We show that Mycobacterium smegmatis is highly resistant to the toxic effects of CO, exhibiting only minor inhibition of growth when cultured in its presence. We profiled the proteome of M. smegmatis during growth in CO, identifying strong induction of cytochrome bd oxidase and members of the dos regulon, but relatively few other changes. We show that the activity of cytochrome bd oxidase is resistant to CO, whereas cytochrome bcc-aa3 oxidase is strongly inhibited by this gas. Consistent with these findings, growth analysis shows that M. smegmatis lacking cytochrome bd oxidase displays a significant growth defect in the presence of CO, while induction of the dos regulon appears to be unimportant for adaptation to CO. Altogether, our findings indicate that M. smegmatis has considerable resistance to CO and benefits from respiratory flexibility to withstand its inhibitory effects. IMPORTANCE Carbon monoxide has an infamous reputation as a toxic gas, and it has been suggested that it has potential as an antibacterial agent. Despite this, how bacteria resist its toxic effects is not well understood. In this study, we investigated how CO influences growth, proteome, and aerobic respiration of wild-type and mutant strains of Mycobacterium smegmatis. We show that this bacterium produces the CO-resistant cytochrome bd oxidase to tolerate poisoning of its CO-sensitive complex IV homolog. Further, we show that aside from this remodeling of its respiratory chain, M. smegmatis makes few other functional changes to its proteome, suggesting it has a high level of inherent resistance to CO.
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Borisov VB, Forte E. Terminal Oxidase Cytochrome bd Protects Bacteria Against Hydrogen Sulfide Toxicity. BIOCHEMISTRY (MOSCOW) 2021; 86:22-32. [PMID: 33705279 DOI: 10.1134/s000629792101003x] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Hydrogen sulfide (H2S) is often called the third gasotransmitter (after nitric oxide and carbon monoxide), or endogenous gaseous signaling molecule. This compound plays important roles in organisms from different taxonomic groups, from bacteria to animals and humans. In mammalian cells, H2S has a cytoprotective effect at nanomolar concentrations, but becomes cytotoxic at higher concentrations. The primary target of H2S is mitochondria. At submicromolar concentrations, H2S inhibits mitochondrial heme-copper cytochrome c oxidase, thereby blocking aerobic respiration and oxidative phosphorylation and eventually leading to cell death. Since the concentration of H2S in the gut is extremely high, the question arises - how can gut bacteria maintain the functioning of their oxygen-dependent respiratory electron transport chains under such conditions? This review provides an answer to this question and discusses the key role of non-canonical bd-type terminal oxidases of the enterobacterium Escherichia coli, a component of the gut microbiota, in maintaining aerobic respiration and growth in the presence of toxic concentrations of H2S in the light of recent experimental data.
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Affiliation(s)
- Vitaliy B Borisov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia.
| | - Elena Forte
- Department of Biochemical Sciences, Sapienza University of Rome, I-00185 Rome, Italy
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Cardiolipin enhances the enzymatic activity of cytochrome bd and cytochrome bo 3 solubilized in dodecyl-maltoside. Sci Rep 2021; 11:8006. [PMID: 33850195 PMCID: PMC8044227 DOI: 10.1038/s41598-021-87354-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Accepted: 03/25/2021] [Indexed: 02/01/2023] Open
Abstract
Cardiolipin (CL) is a lipid that is found in the membranes of bacteria and the inner membranes of mitochondria. CL can increase the activity of integral membrane proteins, in particular components of respiratory pathways. We here report that CL activated detergent-solubilized cytochrome bd, a terminal oxidase from Escherichia coli. CL enhanced the oxygen consumption activity ~ twofold and decreased the apparent KM value for ubiquinol-1 as substrate from 95 µM to 35 µM. Activation by CL was also observed for cytochrome bd from two Gram-positive species, Geobacillus thermodenitrificans and Corynebacterium glutamicum, and for cytochrome bo3 from E. coli. Taken together, CL can enhance the activity of detergent-solubilized cytochrome bd and cytochrome bo3.
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In Escherichia coli Ammonia Inhibits Cytochrome bo3 But Activates Cytochrome bd-I. Antioxidants (Basel) 2020; 10:antiox10010013. [PMID: 33375541 PMCID: PMC7824442 DOI: 10.3390/antiox10010013] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 12/18/2020] [Accepted: 12/21/2020] [Indexed: 12/14/2022] Open
Abstract
Interaction of two redox enzymes of Escherichia coli, cytochrome bo3 and cytochrome bd-I, with ammonium sulfate/ammonia at pH 7.0 and 8.3 was studied using high-resolution respirometry and absorption spectroscopy. At pH 7.0, the oxygen reductase activity of none of the enzymes is affected by the ligand. At pH 8.3, cytochrome bo3 is inhibited by the ligand, with 40% maximum inhibition at 100 mM (NH4)2SO4. In contrast, the activity of cytochrome bd-I at pH 8.3 increases with increasing the ligand concentration, the largest increase (140%) is observed at 100 mM (NH4)2SO4. In both cases, the effector molecule is apparently not NH4+ but NH3. The ligand induces changes in absorption spectra of both oxidized cytochromes at pH 8.3. The magnitude of these changes increases as ammonia concentration is increased, yielding apparent dissociation constants Kdapp of 24.3 ± 2.7 mM (NH4)2SO4 (4.9 ± 0.5 mM NH3) for the Soret region in cytochrome bo3, and 35.9 ± 7.1 and 24.6 ± 12.4 mM (NH4)2SO4 (7.2 ± 1.4 and 4.9 ± 2.5 mM NH3) for the Soret and visible regions, respectively, in cytochrome bd-I. Consistently, addition of (NH4)2SO4 to cells of the E. coli mutant containing cytochrome bd-I as the only terminal oxidase at pH 8.3 accelerates the O2 consumption rate, the highest one (140%) being at 27 mM (NH4)2SO4. We discuss possible molecular mechanisms and physiological significance of modulation of the enzymatic activities by ammonia present at high concentration in the intestines, a niche occupied by E. coli.
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Bioinformatic and experimental evidence for suicidal and catalytic plant THI4s. Biochem J 2020; 477:2055-2069. [PMID: 32441748 DOI: 10.1042/bcj20200297] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 05/20/2020] [Accepted: 05/21/2020] [Indexed: 12/14/2022]
Abstract
Like fungi and some prokaryotes, plants use a thiazole synthase (THI4) to make the thiazole precursor of thiamin. Fungal THI4s are suicide enzymes that destroy an essential active-site Cys residue to obtain the sulfur atom needed for thiazole formation. In contrast, certain prokaryotic THI4s have no active-site Cys, use sulfide as sulfur donor, and are truly catalytic. The presence of a conserved active-site Cys in plant THI4s and other indirect evidence implies that they are suicidal. To confirm this, we complemented the Arabidopsistz-1 mutant, which lacks THI4 activity, with a His-tagged Arabidopsis THI4 construct. LC-MS analysis of tryptic peptides of the THI4 extracted from leaves showed that the active-site Cys was predominantly in desulfurated form, consistent with THI4 having a suicide mechanism in planta. Unexpectedly, transcriptome data mining and deep proteome profiling showed that barley, wheat, and oat have both a widely expressed canonical THI4 with an active-site Cys, and a THI4-like paralog (non-Cys THI4) that has no active-site Cys and is the major type of THI4 in developing grains. Transcriptomic evidence also indicated that barley, wheat, and oat grains synthesize thiamin de novo, implying that their non-Cys THI4s synthesize thiazole. Structure modeling supported this inference, as did demonstration that non-Cys THI4s have significant capacity to complement thiazole auxotrophy in Escherichia coli. There is thus a prima facie case that non-Cys cereal THI4s, like their prokaryotic counterparts, are catalytic thiazole synthases. Bioenergetic calculations show that, relative to suicide THI4s, such enzymes could save substantial energy during the grain-filling period.
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34
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Duzs Á, Miklovics N, Paragi G, Rákhely G, Tóth A. Insights into the catalytic mechanism of type VI sulfide:quinone oxidoreductases. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2020; 1862:148337. [PMID: 33202220 DOI: 10.1016/j.bbabio.2020.148337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 10/09/2020] [Accepted: 11/03/2020] [Indexed: 10/23/2022]
Abstract
Sulfide oxidation is catalyzed by ancient membrane-bound sulfide:quinone oxidoreductases (SQR) which are classified into six different types. For catalysis of sulfide oxidation, all SQRs require FAD cofactor and a redox-active centre in the active site, usually formed between conserved essential cysteines. SQRs of different types have variation in the number and position of cysteines, highlighting the potential for diverse catalytic mechanisms. The photosynthetic purple sulfur bacterium, Thiocapsa roseopersicina contains a type VI SQR enzyme (TrSqrF) having unusual catalytic parameters and four cysteines likely involved in the catalysis. Site-directed mutagenesis was applied to identify the role of cysteines in the catalytic process of TrSqrF. Based on biochemical and kinetic characterization of these TrSqrF variants, Cys121 is identified as crucial for enzyme activity. The cofactor is covalently bound via a heterodisulfide bridge between Cys121 and the C8M group of FAD. Mutation of another cysteine present in all SQRs (Cys332) causes remarkably decreased enzyme activity (14.6% of wild type enzyme) proving important, but non-essential role of this residue in enzyme catalysis. The sulfhydril-blocking agent, iodoacetamide can irreversibly inactivate TrSqrF but only if substrates are present and the enzyme is actively catalyzing its reaction. When the enzyme is inhibited by iodoacetamide, the FAD cofactor is released. The inhibition studies support a mechanism that entails opening and reforming of the heterodisulfide bridge during the catalytic cycle of TrSqrF. Our study thus reports the first detailed structure-function analysis of a type VI SQR enzyme which enables the proposal of a distinct mechanism of sulfide oxidation for this class.
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Affiliation(s)
- Ágnes Duzs
- Institute of Biophysics, Biological Research Centre, Temesvári krt 62., H-6726 Szeged, Hungary; Department of Biotechnology, University of Szeged, Közép fasor 52., H-6726 Szeged, Hungary
| | - Nikolett Miklovics
- Institute of Biophysics, Biological Research Centre, Temesvári krt 62., H-6726 Szeged, Hungary; Department of Biotechnology, University of Szeged, Közép fasor 52., H-6726 Szeged, Hungary; Doctoral School in Biology, University of Szeged, Közép fasor 52., H-6726 Szeged, Hungary
| | - Gábor Paragi
- Institute of Physics, University of Pécs, Ifjúság útja 6., H-7624 Pécs, Hungary; MTA-SZTE Biomimetic Systems Research Group, Department of Medical Chemistry, University of Szeged, Dóm square 8, H-6720 Szeged, Hungary
| | - Gábor Rákhely
- Institute of Biophysics, Biological Research Centre, Temesvári krt 62., H-6726 Szeged, Hungary; Department of Biotechnology, University of Szeged, Közép fasor 52., H-6726 Szeged, Hungary.
| | - András Tóth
- Institute of Biophysics, Biological Research Centre, Temesvári krt 62., H-6726 Szeged, Hungary; Department of Biotechnology, University of Szeged, Közép fasor 52., H-6726 Szeged, Hungary
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Rahman MA, Glasgow JN, Nadeem S, Reddy VP, Sevalkar RR, Lancaster JR, Steyn AJC. The Role of Host-Generated H 2S in Microbial Pathogenesis: New Perspectives on Tuberculosis. Front Cell Infect Microbiol 2020; 10:586923. [PMID: 33330130 PMCID: PMC7711268 DOI: 10.3389/fcimb.2020.586923] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Accepted: 10/13/2020] [Indexed: 12/14/2022] Open
Abstract
For centuries, hydrogen sulfide (H2S) was considered primarily as a poisonous gas and environmental hazard. However, with the discovery of prokaryotic and eukaryotic enzymes for H2S production, breakdown, and utilization, H2S has emerged as an important signaling molecule in a wide range of physiological and pathological processes. Hence, H2S is considered a gasotransmitter along with nitric oxide (•NO) and carbon monoxide (CO). Surprisingly, despite having overlapping functions with •NO and CO, the role of host H2S in microbial pathogenesis is understudied and represents a gap in our knowledge. Given the numerous reports that followed the discovery of •NO and CO and their respective roles in microbial pathogenesis, we anticipate a rapid increase in studies that further define the importance of H2S in microbial pathogenesis, which may lead to new virulence paradigms. Therefore, this review provides an overview of sulfide chemistry, enzymatic production of H2S, and the importance of H2S in metabolism and immunity in response to microbial pathogens. We then describe our current understanding of the role of host-derived H2S in tuberculosis (TB) disease, including its influences on host immunity and bioenergetics, and on Mycobacterium tuberculosis (Mtb) growth and survival. Finally, this review discusses the utility of H2S-donor compounds, inhibitors of H2S-producing enzymes, and their potential clinical significance.
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Affiliation(s)
| | - Joel N Glasgow
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Sajid Nadeem
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Vineel P Reddy
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Ritesh R Sevalkar
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Jack R Lancaster
- Department of Pharmacology and Chemical Biology, Vascular Medicine Institute, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
| | - Adrie J C Steyn
- Africa Health Research Institute, Durban, South Africa.,Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL, United States.,Centers for AIDS Research and Free Radical Biology, University of Alabama at Birmingham, Birmingham, AL, United States
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Walsh BJC, Giedroc DP. H 2S and reactive sulfur signaling at the host-bacterial pathogen interface. J Biol Chem 2020; 295:13150-13168. [PMID: 32699012 PMCID: PMC7504917 DOI: 10.1074/jbc.rev120.011304] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 07/22/2020] [Indexed: 12/13/2022] Open
Abstract
Bacterial pathogens that cause invasive disease in the vertebrate host must adapt to host efforts to cripple their viability. Major host insults are reactive oxygen and reactive nitrogen species as well as cellular stress induced by antibiotics. Hydrogen sulfide (H2S) is emerging as an important player in cytoprotection against these stressors, which may well be attributed to downstream more oxidized sulfur species termed reactive sulfur species (RSS). In this review, we summarize recent work that suggests that H2S/RSS impacts bacterial survival in infected cells and animals. We discuss the mechanisms of biogenesis and clearance of RSS in the context of a bacterial H2S/RSS homeostasis model and the bacterial transcriptional regulatory proteins that act as "sensors" of cellular RSS that maintain H2S/RSS homeostasis. In addition, we cover fluorescence imaging- and MS-based approaches used to detect and quantify RSS in bacterial cells. Last, we discuss proteome persulfidation (S-sulfuration) as a potential mediator of H2S/RSS signaling in bacteria in the context of the writer-reader-eraser paradigm, and progress toward ascribing regulatory significance to this widespread post-translational modification.
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Affiliation(s)
- Brenna J C Walsh
- Department of Chemistry, Indiana University, Bloomington, Indiana, USA
| | - David P Giedroc
- Department of Chemistry, Indiana University, Bloomington, Indiana, USA; Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana, USA.
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García-García JD, Joshi J, Patterson JA, Trujillo-Rodriguez L, Reisch CR, Javanpour AA, Liu CC, Hanson AD. Potential for Applying Continuous Directed Evolution to Plant Enzymes: An Exploratory Study. Life (Basel) 2020; 10:E179. [PMID: 32899502 PMCID: PMC7555113 DOI: 10.3390/life10090179] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 08/31/2020] [Accepted: 09/01/2020] [Indexed: 12/22/2022] Open
Abstract
Plant evolution has produced enzymes that may not be optimal for maximizing yield and quality in today's agricultural environments and plant biotechnology applications. By improving enzyme performance, it should be possible to alleviate constraints on yield and quality currently imposed by kinetic properties or enzyme instability. Enzymes can be optimized more quickly than naturally possible by applying directed evolution, which entails mutating a target gene in vitro and screening or selecting the mutated gene products for the desired characteristics. Continuous directed evolution is a more efficient and scalable version that accomplishes the mutagenesis and selection steps simultaneously in vivo via error-prone replication of the target gene and coupling of the host cell's growth rate to the target gene's function. However, published continuous systems require custom plasmid assembly, and convenient multipurpose platforms are not available. We discuss two systems suitable for continuous directed evolution of enzymes, OrthoRep in Saccharomyces cerevisiae and EvolvR in Escherichia coli, and our pilot efforts to adapt each system for high-throughput plant enzyme engineering. To test our modified systems, we used the thiamin synthesis enzyme THI4, previously identified as a prime candidate for improvement. Our adapted OrthoRep system shows promise for efficient plant enzyme engineering.
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Affiliation(s)
| | - Jaya Joshi
- Horticultural Sciences Department, University of Florida, Gainesville, FL 32611, USA;
| | - Jenelle A. Patterson
- Horticultural Sciences Department, University of Florida, Gainesville, FL 32611, USA;
| | - Lidimarie Trujillo-Rodriguez
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32603, USA; (L.T.-R.); (C.R.R.)
| | - Christopher R. Reisch
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32603, USA; (L.T.-R.); (C.R.R.)
| | - Alex A. Javanpour
- Department of Biomedical Engineering, University of California, Irvine, CA 92617, USA; (A.A.J.); (C.C.L.)
| | - Chang C. Liu
- Department of Biomedical Engineering, University of California, Irvine, CA 92617, USA; (A.A.J.); (C.C.L.)
- Department of Chemistry, University of California, Irvine, CA 92617, USA
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697, USA
| | - Andrew D. Hanson
- Horticultural Sciences Department, University of Florida, Gainesville, FL 32611, USA;
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38
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Walsh BJC, Wang J, Edmonds KA, Palmer LD, Zhang Y, Trinidad JC, Skaar EP, Giedroc DP. The Response of Acinetobacter baumannii to Hydrogen Sulfide Reveals Two Independent Persulfide-Sensing Systems and a Connection to Biofilm Regulation. mBio 2020; 11:e01254-20. [PMID: 32576676 PMCID: PMC7315123 DOI: 10.1128/mbio.01254-20] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Accepted: 05/19/2020] [Indexed: 12/13/2022] Open
Abstract
Acinetobacter baumannii is an opportunistic nosocomial pathogen that is the causative agent of several serious infections in humans, including pneumonia, sepsis, and wound and burn infections. A. baumannii is also capable of forming proteinaceous biofilms on both abiotic and epithelial cell surfaces. Here, we investigate the response of A. baumannii toward sodium sulfide (Na2S), known to be associated with some biofilms at oxic/anoxic interfaces. The addition of exogenous inorganic sulfide reveals that A. baumannii encodes two persulfide-sensing transcriptional regulators, a primary σ54-dependent transcriptional activator (FisR), and a secondary system controlled by the persulfide-sensing biofilm growth-associated repressor (BigR), which is only induced by sulfide in a fisR deletion strain. FisR activates an operon encoding a sulfide oxidation/detoxification system similar to that characterized previously in Staphylococcus aureus, while BigR regulates a secondary persulfide dioxygenase (PDO2) as part of yeeE-yedE-pdo2 sulfur detoxification operon, found previously in Serratia spp. Global S-sulfuration (persulfidation) mapping of the soluble proteome reveals 513 persulfidation targets well beyond FisR-regulated genes and includes five transcriptional regulators, most notably the master biofilm regulator BfmR and a poorly characterized catabolite regulatory protein (Crp). Both BfmR and Crp are well known to impact biofilm formation in A. baumannii and other organisms, respectively, suggesting that persulfidation of these regulators may control their activities. The implications of these findings on bacterial sulfide homeostasis, persulfide signaling, and biofilm formation are discussed.IMPORTANCE Although hydrogen sulfide (H2S) has long been known as a respiratory poison, recent reports in numerous bacterial pathogens reveal that H2S and more downstream oxidized forms of sulfur collectedly termed reactive sulfur species (RSS) function as antioxidants to combat host efforts to clear the infection. Here, we present a comprehensive analysis of the transcriptional and proteomic response of A. baumannii to exogenous sulfide as a model for how this important human pathogen manages sulfide/RSS homeostasis. We show that A. baumannii is unique in that it encodes two independent persulfide sensing and detoxification pathways that govern the speciation of bioactive sulfur in cells. The secondary persulfide sensor, BigR, impacts the expression of biofilm-associated genes; in addition, we identify two other transcriptional regulators known or projected to regulate biofilm formation, BfmR and Crp, as highly persulfidated in sulfide-exposed cells. These findings significantly strengthen the connection between sulfide homeostasis and biofilm formation in an important human pathogen.
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Affiliation(s)
- Brenna J C Walsh
- Department of Chemistry, Indiana University, Bloomington, Indiana, USA
| | - Jiefei Wang
- Department of Chemistry, Indiana University, Bloomington, Indiana, USA
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana, USA
| | | | - Lauren D Palmer
- Department of Pathology, Microbiology and Immunology, and Vanderbilt Institute for Infection, Immunology and Inflammation, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Yixiang Zhang
- Laboratory for Biological Mass Spectrometry, Indiana University, Bloomington, Indiana, USA
| | - Jonathan C Trinidad
- Laboratory for Biological Mass Spectrometry, Indiana University, Bloomington, Indiana, USA
| | - Eric P Skaar
- Department of Pathology, Microbiology and Immunology, and Vanderbilt Institute for Infection, Immunology and Inflammation, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - David P Giedroc
- Department of Chemistry, Indiana University, Bloomington, Indiana, USA
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana, USA
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39
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Zhou Y, Imlay JA. Escherichia coli K-12 Lacks a High-Affinity Assimilatory Cysteine Importer. mBio 2020; 11:e01073-20. [PMID: 32518189 PMCID: PMC7373191 DOI: 10.1128/mbio.01073-20] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2020] [Accepted: 05/05/2020] [Indexed: 01/09/2023] Open
Abstract
The most direct route by which microbes might assimilate sulfur would be by importing cysteine. However, alone among the amino acids, cysteine does not have well-characterized importers. We determined that Escherichia coli can rapidly import cysteine, but in our experiments, it did so primarily through the LIV ATP-driven system that is dedicated to branched-chain amino acids. The affinity of this system for cysteine is far lower than for Leu, Ile, and Val, and so in their presence, cysteine is excluded. Thus, this transport is unlikely to be relevant in natural environments. Growth studies, transcriptomics, and transport assays failed to detect any high-affinity importer that is dedicated to cysteine assimilation. Enteric bacteria do not contain the putative cysteine importer that was identified in Campylobacter jejuni This situation is surprising, because E. coli deploys ion- and/or ATP-driven transporters that import cystine, the oxidized form of cysteine, with high affinity and specificity. We conjecture that in oxic environments, molecular oxygen oxidizes environmental cysteine to cystine, which E. coli imports. In anoxic environments where cysteine is stable, the cell chooses to assimilate hydrogen sulfide instead. Calculations suggest that this alternative is almost as economical, and it avoids the toxic effects that can result when excess cysteine enters the cell.IMPORTANCE This investigation discovered that Escherichia coli lacks a transporter dedicated to the assimilation of cysteine, an outcome that is in striking contrast to the many transporters devoted to the other 19 amino acids. We ascribe the lack of a high-affinity cysteine importer to two considerations. First, the chemical reactivity of this amino acid is unique, and its poorly controlled import can have adverse consequences for the cell. Second, our analysis suggests that the economics of biosynthesis depend sharply upon whether the cell is respiring or fermenting. In the anoxic habitats in which cysteine might be found, the value of import versus biosynthesis is strongly reduced compared to that in oxic habitats. These studies may explain why bacteria choose to synthesize rather than to import other useful biomolecules as well.
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Affiliation(s)
- Yidan Zhou
- Department of Microbiology, University of Illinois, Urbana, Illinois, USA
| | - James A Imlay
- Department of Microbiology, University of Illinois, Urbana, Illinois, USA
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40
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Saini V, Chinta KC, Reddy VP, Glasgow JN, Stein A, Lamprecht DA, Rahman MA, Mackenzie JS, Truebody BE, Adamson JH, Kunota TTR, Bailey SM, Moellering DR, Lancaster JR, Steyn AJC. Hydrogen sulfide stimulates Mycobacterium tuberculosis respiration, growth and pathogenesis. Nat Commun 2020; 11:557. [PMID: 31992699 PMCID: PMC6987094 DOI: 10.1038/s41467-019-14132-y] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Accepted: 12/13/2019] [Indexed: 01/23/2023] Open
Abstract
Hydrogen sulfide (H2S) is involved in numerous pathophysiological processes and shares overlapping functions with CO and •NO. However, the importance of host-derived H2S in microbial pathogenesis is unknown. Here we show that Mtb-infected mice deficient in the H2S-producing enzyme cystathionine β-synthase (CBS) survive longer with reduced organ burden, and that pharmacological inhibition of CBS reduces Mtb bacillary load in mice. High-resolution respirometry, transcriptomics and mass spectrometry establish that H2S stimulates Mtb respiration and bioenergetics predominantly via cytochrome bd oxidase, and that H2S reverses •NO-mediated inhibition of Mtb respiration. Further, exposure of Mtb to H2S regulates genes involved in sulfur and copper metabolism and the Dos regulon. Our results indicate that Mtb exploits host-derived H2S to promote growth and disease, and suggest that host-directed therapies targeting H2S production may be potentially useful for the management of tuberculosis and other microbial infections. The importance of host-produced hydrogen sulfide (H2S) in microbial pathogenesis is poorly understood. Here, Saini et al. show that H2S alters Mycobacterium tuberculosis (Mtb) central metabolism, stimulates respiration to promote growth and TB disease, and upregulates the Dos regulon.
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Affiliation(s)
- Vikram Saini
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL, USA.,Center for Free Radical Biology, University of Alabama at Birmingham, Birmingham, AL, USA.,Laboratory of Infection Biology and Translational Research, Department of Biotechnology, All India Institute of Medical Sciences, New Delhi, India
| | - Krishna C Chinta
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Vineel P Reddy
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Joel N Glasgow
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Asaf Stein
- Department of Environment Health Sciences, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Dirk A Lamprecht
- Africa Health Research Institute, Durban, South Africa.,Janssen Infectious Diseases and Vaccines, Janssen Pharmaceutica NV, Beerse, Belgium
| | | | | | | | | | | | - Shannon M Bailey
- Department of Environment Health Sciences, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Douglas R Moellering
- Center for Free Radical Biology, University of Alabama at Birmingham, Birmingham, AL, USA.,Department of Nutrition Sciences, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Jack R Lancaster
- Departments of Pharmacology and Chemical Biology, Medicine, and Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Adrie J C Steyn
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL, USA. .,Center for Free Radical Biology, University of Alabama at Birmingham, Birmingham, AL, USA. .,Africa Health Research Institute, Durban, South Africa. .,Center for AIDS Research, University of Alabama at Birmingham, Birmingham, AL, USA.
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41
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Maarsingh JD, Yang S, Park JG, Haydel SE. Comparative transcriptomics reveals PrrAB-mediated control of metabolic, respiration, energy-generating, and dormancy pathways in Mycobacterium smegmatis. BMC Genomics 2019; 20:942. [PMID: 31810444 PMCID: PMC6898941 DOI: 10.1186/s12864-019-6105-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Accepted: 09/13/2019] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND Mycobacterium smegmatis is a saprophytic bacterium frequently used as a genetic surrogate to study pathogenic Mycobacterium tuberculosis. The PrrAB two-component genetic regulatory system is essential in M. tuberculosis and represents an attractive therapeutic target. In this study, transcriptomic analysis (RNA-seq) of an M. smegmatis ΔprrAB mutant was used to define the PrrAB regulon and provide insights into the essential nature of PrrAB in M. tuberculosis. RESULTS RNA-seq differential expression analysis of M. smegmatis wild-type (WT), ΔprrAB mutant, and complementation strains revealed that during in vitro exponential growth, PrrAB regulates 167 genes (q < 0.05), 57% of which are induced in the WT background. Gene ontology and cluster of orthologous groups analyses showed that PrrAB regulates genes participating in ion homeostasis, redox balance, metabolism, and energy production. PrrAB induced transcription of dosR (devR), a response regulator gene that promotes latent infection in M. tuberculosis and 21 of the 25 M. smegmatis DosRS regulon homologues. Compared to the WT and complementation strains, the ΔprrAB mutant exhibited an exaggerated delayed growth phenotype upon exposure to potassium cyanide and respiratory inhibition. Gene expression profiling correlated with these growth deficiency results, revealing that PrrAB induces transcription of the high-affinity cytochrome bd oxidase genes under both aerobic and hypoxic conditions. ATP synthesis was ~ 64% lower in the ΔprrAB mutant relative to the WT strain, further demonstrating that PrrAB regulates energy production. CONCLUSIONS The M. smegmatis PrrAB two-component system regulates respiratory and oxidative phosphorylation pathways, potentially to provide tolerance against the dynamic environmental conditions experienced in its natural ecological niche. PrrAB positively regulates ATP levels during exponential growth, presumably through transcriptional activation of both terminal respiratory branches (cytochrome c bc1-aa3 and cytochrome bd oxidases), despite transcriptional repression of ATP synthase genes. Additionally, PrrAB positively regulates expression of the dormancy-associated dosR response regulator genes in an oxygen-independent manner, which may serve to fine-tune sensory perception of environmental stimuli associated with metabolic repression.
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Affiliation(s)
- Jason D Maarsingh
- School of Life Sciences, Arizona State University, Tempe, AZ, USA.,Department of Obstetrics and Gynecology, College of Medicine-Phoenix, University of Arizona, Phoenix, AZ, USA
| | - Shanshan Yang
- Bioinformatics Core, Knowledge Enterprise Development, Arizona State University, Tempe, AZ, USA
| | - Jin G Park
- The Biodesign Institute Virginia G. Piper Center for Personalized Diagnostics, Arizona State University, Tempe, AZ, USA
| | - Shelley E Haydel
- School of Life Sciences, Arizona State University, Tempe, AZ, USA. .,The Biodesign Institute Center for Immunotherapy, Vaccines and Virotherapy, Arizona State University, Tempe, AZ, USA.
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42
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Downs DM. Balancing cost and benefit: How E. coli cleverly averts disulfide stress caused by cystine. Mol Microbiol 2019; 113:1-3. [PMID: 31710395 DOI: 10.1111/mmi.14422] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2019] [Revised: 11/07/2019] [Accepted: 11/07/2019] [Indexed: 01/08/2023]
Abstract
Building a robust, stable network must include strategies to minimize perturbations caused by environmental stress, while optimizing cellular fitness. The introduction of oxygen into the Earth's atmosphere brought challenges for the microbes that had evolved enzyme machinery and metabolic network stability in the anoxic world. Unable to generate new enzyme paradigms and metabolic networks de novo, organisms have evolved strategies to neutralize the impact of oxygen that can be added to and integrated into the existing metabolic framework. This issue of Molecular Microbiology includes a paper by Korshunov et al. in which the authors describe an elegant strategy that Escherichia coli has evolved to minimize metabolic stress that results from the acquisition and use of cystine, the oxidized form of cysteine, as a source of cellular sulfur. This study highlights how a strategy involving both cost and benefit can result in a functional, but energy intensive mechanism for this bacterium to thrive in an oxic world.
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Affiliation(s)
- Diana M Downs
- Microbiology Department, University of Georgia, Athens, GA, USA
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43
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Mascolo L, Bald D. Cytochrome bd in Mycobacterium tuberculosis: A respiratory chain protein involved in the defense against antibacterials. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2019; 152:55-63. [PMID: 31738981 DOI: 10.1016/j.pbiomolbio.2019.11.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Accepted: 11/12/2019] [Indexed: 12/27/2022]
Abstract
The branched respiratory chain of Mycobacterium tuberculosis has attracted attention as a highly promising target for next-generation antibacterials. This system includes two terminal oxidases of which the exclusively bacterial cytochrome bd represents the less energy-efficient one. Albeit dispensable for growth under standard laboratory conditions, cytochrome bd is important during environmental stress. In this review, we discuss the role of cytochrome bd during infection of the mammalian host and in the defense against antibacterials. Deeper insight into the biochemistry of mycobacterial cytochrome bd is needed to understand the physiological role of this bacteria-specific defense factor. Conversely, cytochrome bd may be utilized to gain information on mycobacterial physiology in vitro and during host infection. Knowledge-based manipulation of cytochrome bd function may assist in designing the next-generation tuberculosis combination chemotherapy.
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Affiliation(s)
- Ludovica Mascolo
- Department of Molecular Cell Biology, Amsterdam Institute for Molecules, Medicines and Systems, Faculty of Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1108, 1081 HZ Amsterdam, The Netherlands
| | - Dirk Bald
- Department of Molecular Cell Biology, Amsterdam Institute for Molecules, Medicines and Systems, Faculty of Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1108, 1081 HZ Amsterdam, The Netherlands.
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Korshunov S, Imlay KRC, Imlay JA. Cystine import is a valuable but risky process whose hazards Escherichia coli minimizes by inducing a cysteine exporter. Mol Microbiol 2019; 113:22-39. [PMID: 31612555 PMCID: PMC7007315 DOI: 10.1111/mmi.14403] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/12/2019] [Indexed: 12/24/2022]
Abstract
The structure of free cysteine makes it vulnerable to oxidation by molecular oxygen; consequently, organisms that live in oxic habitats have acquired the ability to import cystine as a sulfur source. We show that cystine imported into Escherichia coli can transfer disulfide bonds to cytoplasmic proteins. To minimize this problem, the imported cystine is rapidly reduced. However, this conversion of cystine to cysteine precludes product inhibition of the importer, so cystine import continues into cells that are already sated with cysteine. The burgeoning cysteine pool is itself hazardous, as cysteine promotes the formation of reactive oxygen species, triggers sulfide production and competitively inhibits a key enzyme in the isoleucine biosynthetic pathway. The Lrp transcription factor senses the excess cysteine and induces AlaE, an export protein that pumps cysteine back out of the cell until transcriptional controls succeed in lowering the amount of the importer. While it lasts, the overall phenomenon roughly doubles the NADPH demand of the cell. It comprises another example of the incompatibility of the reduced cytoplasms of microbes with the oxic world in which they dwell. It also reveals one natural source of cytoplasmic disulfide stress and sheds light on a role for broad-spectrum amino acid exporters.
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Affiliation(s)
- Sergey Korshunov
- Department of Microbiology, University of Illinois, Urbana, IL, 61801, USA
| | | | - James A Imlay
- Department of Microbiology, University of Illinois, Urbana, IL, 61801, USA
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45
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In the respiratory chain of Escherichia coli cytochromes bd-I and bd-II are more sensitive to carbon monoxide inhibition than cytochrome bo 3. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2019; 1860:148088. [PMID: 31669488 DOI: 10.1016/j.bbabio.2019.148088] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Revised: 09/27/2019] [Accepted: 10/18/2019] [Indexed: 11/23/2022]
Abstract
Bacteria can not only encounter carbon monoxide (CO) in their habitats but also produce the gas endogenously. Bacterial respiratory oxidases, thus, represent possible targets for CO. Accordingly, host macrophages were proposed to produce CO and release it into the surrounding microenvironment to sense viable bacteria through a mechanism that in Escherichia (E.) coli was suggested to involve the targeting of a bd-type respiratory oxidase by CO. The aerobic respiratory chain of E. coli possesses three terminal quinol:O2-oxidoreductases: the heme-copper oxidase bo3 and two copper-lacking bd-type oxidases, bd-I and bd-II. Heme-copper and bd-type oxidases differ in the mechanism and efficiency of proton motive force generation and in resistance to oxidative and nitrosative stress, cyanide and hydrogen sulfide. Here, we investigated at varied O2 concentrations the effect of CO gas on the O2 reductase activity of the purified cytochromes bo3, bd-I and bd-II of E. coli. We found that CO, in competition with O2, reversibly inhibits the three enzymes. The inhibition constants Ki for the bo3, bd-I and bd-II oxidases are 2.4 ± 0.3, 0.04 ± 0.01 and 0.2 ± 0.1 μM CO, respectively. Thus, in E. coli, bd-type oxidases are more sensitive to CO inhibition than the heme-copper cytochrome bo3. The possible physiological consequences of this finding are discussed.
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46
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Smirnova GV, Tyulenev AV, Bezmaternykh KV, Muzyka NG, Ushakov VY, Oktyabrsky ON. Cysteine homeostasis under inhibition of protein synthesis in Escherichia coli cells. Amino Acids 2019; 51:1577-1592. [PMID: 31617110 DOI: 10.1007/s00726-019-02795-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Accepted: 10/02/2019] [Indexed: 01/23/2023]
Abstract
Increased intracellular cysteine poses a potential danger to cells due to the high ability of cysteine to reduce free iron and promote the Fenton reaction. Here, we studied ways to maintain cysteine homeostasis in E. coli cells while inhibiting protein synthesis with valine or chloramphenicol. When growing wild-type bacteria on minimal medium with sulfate, an excess of cysteine resulting from the inhibition of protein synthesis is mainly incorporated into glutathione (up to 90%), which, therefore, can be considered as cysteine buffer. The share of hydrogen sulfide, which is the product of cysteine degradation by cysteine synthase B (CysM), does not exceed 1-3%, the rest falls on free cysteine, exported from cells. As a result, intracellular free cysteine is maintained at a low level (about 0.1 mM). The lack of glutathione in the gshA mutant increases H2S production and excretion of cysteine and leads to a threefold increase in the level of intracellular cysteine in response to valine and chloramphenicol. The relA mutants, exposed to valine, produce more H2S, dramatically accelerate the export of glutathione and accumulate more cysteine in the cytoplasm than their parent, which indicates that the regulatory nucleotide (p)ppGpp is involved in maintaining cysteine homeostasis. Disruption of cysteine homeostasis in gshA and relA mutants increases their sensitivity to peroxide stress.
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Affiliation(s)
- Galina V Smirnova
- Institute of Ecology and Genetics of Microorganisms, Russian Academy of Sciences, Golev Street 13, 614081, Perm, Russia.
| | - Aleksey V Tyulenev
- Institute of Ecology and Genetics of Microorganisms, Russian Academy of Sciences, Golev Street 13, 614081, Perm, Russia
| | - Kseniya V Bezmaternykh
- Institute of Ecology and Genetics of Microorganisms, Russian Academy of Sciences, Golev Street 13, 614081, Perm, Russia
| | - Nadezda G Muzyka
- Institute of Ecology and Genetics of Microorganisms, Russian Academy of Sciences, Golev Street 13, 614081, Perm, Russia
| | - Vadim Y Ushakov
- Institute of Ecology and Genetics of Microorganisms, Russian Academy of Sciences, Golev Street 13, 614081, Perm, Russia.,Perm State University, Bukireva Street 15, 614990, Perm, Russia
| | - Oleg N Oktyabrsky
- Institute of Ecology and Genetics of Microorganisms, Russian Academy of Sciences, Golev Street 13, 614081, Perm, Russia.,Perm National Research Polytechnic University, Komsomolsky Pr. 29, 614990, Perm, Russia
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47
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Wang J, Guo X, Li H, Qi H, Qian J, Yan S, Shi J, Niu W. Hydrogen Sulfide From Cysteine Desulfurase, Not 3-Mercaptopyruvate Sulfurtransferase, Contributes to Sustaining Cell Growth and Bioenergetics in E. coli Under Anaerobic Conditions. Front Microbiol 2019; 10:2357. [PMID: 31681220 PMCID: PMC6797615 DOI: 10.3389/fmicb.2019.02357] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2019] [Accepted: 09/27/2019] [Indexed: 01/09/2023] Open
Abstract
Endogenous hydrogen sulfide (H2S), which is primarily generated by 3-mercaptopyruvate sulfurtransferase (3-MST) in Escherichia coli (E. coli) under aerobic conditions, renders bacteria highly resistant to oxidative stress. However, the biosynthetic pathway and physiological role of this gas under anaerobic conditions remains largely unknown. In the present study, we demonstrate that cysteine desulfurase (IscS), not 3-MST, is the primary source of endogenous H2S in E. coli under anaerobic conditions. A significant decrease in H2S production under anaerobic conditions was observed in E. coli upon deletion of IscS, but not in 3-MST-deficient bacteria (ΔmstA). Furthermore, the H2S-producing activity of recombinant IscS using L-cysteine as a substrate exhibited an approximately 2.6-fold increase in the presence of dithiothreitol (DTT), indicating that H2S production catalyzed by IscS was greatly increased under reducing conditions. The activity of IscS was regulated under the different redox conditions and the midpoint redox potential was determined to be −329 ± 1.6 mV. Moreover, in E. coli cells H2S production from IscS is regulated under oxidative and reductive stress. A mutant E. coli (ΔiscS) strain lacking a chromosomal copy of the IscS-encoding gene iscS showed significant growth defects and low levels of ATP under both aerobic and anaerobic conditions. The growth defects could be fully restored after addition of 500 μM Na2S (an H2S donor) under anaerobic conditions, but not by the addition of cysteine, sodium sulfite or sodium sulfate. We also showed that the addition of 500 μM Na2S to culture medium stimulates ATP synthesis in the mutant E. coli (ΔiscS) strain in the logarithmic growth phase but suppresses ATP synthesis in wild-type E. coli. Our results reveal a new H2S-producing pathway in E. coli under anaerobic conditions and show that hydrogen sulfide from IscS contributes to sustaining cell growth and bioenergetics under oxygen-deficient conditions.
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Affiliation(s)
- Jun Wang
- School of Life Sciences, Northwestern Polytechnical University, Xi'an, China
| | - Xin Guo
- School of Life Sciences, Northwestern Polytechnical University, Xi'an, China
| | - Heng Li
- School of Life Sciences, Northwestern Polytechnical University, Xi'an, China
| | - Haizhen Qi
- School of Life Sciences, Northwestern Polytechnical University, Xi'an, China
| | - Jing Qian
- School of Life Sciences, Northwestern Polytechnical University, Xi'an, China
| | - Shasha Yan
- School of Life Sciences, Northwestern Polytechnical University, Xi'an, China
| | - Junling Shi
- School of Life Sciences, Northwestern Polytechnical University, Xi'an, China
| | - Weining Niu
- School of Life Sciences, Northwestern Polytechnical University, Xi'an, China
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48
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Zinc Toxicity and Iron-Sulfur Cluster Biogenesis in Escherichia coli. Appl Environ Microbiol 2019; 85:AEM.01967-18. [PMID: 30824435 PMCID: PMC6495748 DOI: 10.1128/aem.01967-18] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Accepted: 02/01/2019] [Indexed: 12/20/2022] Open
Abstract
While zinc is an essential trace metal in biology, excess zinc is toxic to organisms. Previous studies have shown that zinc toxicity is associated with disruption of the [4Fe-4S] clusters in various dehydratases in Escherichia coli Here, we report that the intracellular zinc overload in E. coli cells inhibits iron-sulfur cluster biogenesis without affecting the preassembled iron-sulfur clusters in proteins. Among the housekeeping iron-sulfur cluster assembly proteins encoded by the gene cluster iscSUA-hscBA-fdx-iscX in E. coli cells, the scaffold IscU, the iron chaperone IscA, and ferredoxin have strong zinc binding activity in cells, suggesting that intracellular zinc overload inhibits iron-sulfur cluster biogenesis by binding to the iron-sulfur cluster assembly proteins. Mutations of the conserved cysteine residues to serine in IscA, IscU, or ferredoxin completely abolish the zinc binding activity of the proteins, indicating that zinc can compete with iron or iron-sulfur cluster binding in IscA, IscU, and ferredoxin and block iron-sulfur cluster biogenesis. Furthermore, intracellular zinc overload appears to emulate the slow-growth phenotype of the E. coli mutant cells with deletion of the iron-sulfur cluster assembly proteins IscU, IscA, and ferredoxin. Our results suggest that intracellular zinc overload inhibits iron-sulfur cluster biogenesis by targeting the iron-sulfur cluster assembly proteins IscU, IscA, and ferredoxin in E. coli cells.IMPORTANCE Zinc toxicity has been implicated in causing various human diseases. High concentrations of zinc can also inhibit bacterial cell growth. However, the underlying mechanism has not been fully understood. Here, we report that zinc overload in Escherichia coli cells inhibits iron-sulfur cluster biogenesis by targeting specific iron-sulfur cluster assembly proteins. Because iron-sulfur proteins are involved in diverse physiological processes, the zinc-mediated inhibition of iron-sulfur cluster biogenesis could be largely responsible for the zinc-mediated cytotoxicity. Our finding provides new insights on how intracellular zinc overload may inhibit cellular functions in bacteria.
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49
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Sun J, Sigler CL, Beaudoin GAW, Joshi J, Patterson JA, Cho KH, Ralat MA, Gregory JF, Clark DG, Deng Z, Colquhoun TA, Hanson AD. Parts-Prospecting for a High-Efficiency Thiamin Thiazole Biosynthesis Pathway. PLANT PHYSIOLOGY 2019; 179:958-968. [PMID: 30337452 PMCID: PMC6393793 DOI: 10.1104/pp.18.01085] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 10/10/2018] [Indexed: 05/04/2023]
Abstract
Plants synthesize the thiazole precursor of thiamin (cThz-P) via THIAMIN4 (THI4), a suicide enzyme that mediates one reaction cycle and must then be degraded and resynthesized. It has been estimated that this THI4 turnover consumes 2% to 12% of the maintenance energy budget and that installing an energy-efficient alternative pathway could substantially increase crop yield potential. Available data point to two natural alternatives to the suicidal THI4 pathway: (i) nonsuicidal prokaryotic THI4s that lack the active-site Cys residue on which suicide activity depends, and (ii) an uncharacterized thiazole synthesis pathway in flowers of the tropical arum lily Caladium bicolor that enables production and emission of large amounts of the cThz-P analog 4-methyl-5-vinylthiazole (MVT). We used functional complementation of an Escherichia coli ΔthiG strain to identify a nonsuicidal bacterial THI4 (from Thermovibrio ammonificans) that can function in conditions like those in plant cells. We explored whether C. bicolor synthesizes MVT de novo via a novel route, via a suicidal or a nonsuicidal THI4, or by catabolizing thiamin. Analysis of developmental changes in MVT emission, extractable MVT, thiamin level, and THI4 expression indicated that C. bicolor flowers make MVT de novo via a massively expressed THI4 and that thiamin is not involved. Functional complementation tests indicated that C. bicolor THI4, which has the active-site Cys needed to operate suicidally, may be capable of suicidal and - in hypoxic conditions - nonsuicidal operation. T. ammonificans and C. bicolor THI4s are thus candidate parts for rational redesign or directed evolution of efficient, nonsuicidal THI4s for use in crop improvement.
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Affiliation(s)
- Jiayi Sun
- Horticultural Sciences Department, University of Florida, Gainesville, Florida 32611
| | - Cindy L Sigler
- Department of Environmental Horticulture, University of Florida, Gainesville, Florida 32611
| | | | - Jaya Joshi
- Horticultural Sciences Department, University of Florida, Gainesville, Florida 32611
| | - Jenelle A Patterson
- Horticultural Sciences Department, University of Florida, Gainesville, Florida 32611
| | - Keun H Cho
- Department of Environmental Horticulture, University of Florida, Gainesville, Florida 32611
| | - Maria A Ralat
- Department of Food Science and Human Nutrition, University of Florida, Gainesville, Florida 32611
| | - Jesse F Gregory
- Department of Food Science and Human Nutrition, University of Florida, Gainesville, Florida 32611
| | - David G Clark
- Department of Environmental Horticulture, University of Florida, Gainesville, Florida 32611
| | - Zhanao Deng
- Gulf Coast Research and Education Center, Department of Environmental Horticulture, University of Florida, Wimauma, Florida 33598
| | - Thomas A Colquhoun
- Department of Environmental Horticulture, University of Florida, Gainesville, Florida 32611
| | - Andrew D Hanson
- Horticultural Sciences Department, University of Florida, Gainesville, Florida 32611
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50
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Taylor AJ, Kelly DJ. The function, biogenesis and regulation of the electron transport chains in Campylobacter jejuni: New insights into the bioenergetics of a major food-borne pathogen. Adv Microb Physiol 2019; 74:239-329. [PMID: 31126532 DOI: 10.1016/bs.ampbs.2019.02.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Campylobacter jejuni is a zoonotic Epsilonproteobacterium that grows in the gastrointestinal tract of birds and mammals, and is the most frequent cause of food-borne bacterial gastroenteritis worldwide. As an oxygen-sensitive microaerophile, C. jejuni has to survive high environmental oxygen tensions, adapt to oxygen limitation in the host intestine and resist host oxidative attack. Despite its small genome size, C. jejuni is a versatile and metabolically active pathogen, with a complex and highly branched set of respiratory chains allowing the use of a wide range of electron donors and alternative electron acceptors in addition to oxygen, including fumarate, nitrate, nitrite, tetrathionate and N- or S-oxides. Several novel enzymes participate in these electron transport chains, including a tungsten containing formate dehydrogenase, a Complex I that uses flavodoxin and not NADH, a periplasmic facing fumarate reductase and a cytochrome c tetrathionate reductase. This review presents an updated description of the composition and bioenergetics of these various respiratory chains as they are currently understood, including recent work that gives new insights into energy conservation during electron transport to various alternative electron acceptors. The regulation of synthesis and assembly of the electron transport chains is also discussed. A deeper appreciation of the unique features of the respiratory systems of C. jejuni may be helpful in informing strategies to control this important pathogen.
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Affiliation(s)
- Aidan J Taylor
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Western Bank, Sheffield S10 2TN, UK
| | - David J Kelly
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Western Bank, Sheffield S10 2TN, UK
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