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Chatton E, Labasque T, de La Bernardie J, Guihéneuf N, Bour O, Aquilina L. Field Continuous Measurement of Dissolved Gases with a CF-MIMS: Applications to the Physics and Biogeochemistry of Groundwater Flow. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:846-854. [PMID: 27936737 DOI: 10.1021/acs.est.6b03706] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
In the perspective of a temporal and spatial exploration of aquatic environments (surface and groundwater), we developed a technique for field continuous measurements of dissolved gases with a precision better than 1% for N2, O2, CO2, He, Ar, 2% for Kr, 8% for Xe, and 3% for CH4, N2O and Ne. With a large resolution (from 1 × 10-9 to 1 × 10-2 ccSTP/g) and a capability of high frequency analysis (1 measure every 2 s), the CF-MIMS (Continuous Flow Membrane Inlet Mass Spectrometer) is an innovative tool allowing the investigation of a large panel of hydrological and biogeochemical processes in aquatic systems. Based on the available MIMS technology, this study introduces the development of the CF-MIMS (conception for field experiments, membrane choices, ionization) and an original calibration procedure allowing the quantification of mass spectral overlaps and temperature effects on membrane permeability. This study also presents two field applications of the CF-MIMS involving the well-logging of dissolved gases and the implementation of groundwater tracer tests with dissolved 4He. The results demonstrate the analytical capabilities of the CF-MIMS in the field. Therefore, the CF-MIMS is a valuable tool for the field characterization of biogeochemical reactivity, aquifer transport properties, groundwater recharge, groundwater residence time and aquifer-river exchanges from few hours to several weeks experiments.
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Affiliation(s)
- Eliot Chatton
- OSUR-UMR6118 Géosciences Rennes, Université de Rennes 1 and Centre National de la Recherche Scientifique , Rennes, France
| | - Thierry Labasque
- OSUR-UMR6118 Géosciences Rennes, Université de Rennes 1 and Centre National de la Recherche Scientifique , Rennes, France
| | - Jérôme de La Bernardie
- OSUR-UMR6118 Géosciences Rennes, Université de Rennes 1 and Centre National de la Recherche Scientifique , Rennes, France
| | - Nicolas Guihéneuf
- OSUR-UMR6118 Géosciences Rennes, Université de Rennes 1 and Centre National de la Recherche Scientifique , Rennes, France
- University of Guelph , 50 Stone Road East, Guelph, Ontario Canada
| | - Olivier Bour
- OSUR-UMR6118 Géosciences Rennes, Université de Rennes 1 and Centre National de la Recherche Scientifique , Rennes, France
| | - Luc Aquilina
- OSUR-UMR6118 Géosciences Rennes, Université de Rennes 1 and Centre National de la Recherche Scientifique , Rennes, France
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Bruggeman PJ, Kushner MJ, Locke BR, Gardeniers JGE, Graham WG, Graves DB, Hofman-Caris RCHM, Maric D, Reid JP, Ceriani E, Fernandez Rivas D, Foster JE, Garrick SC, Gorbanev Y, Hamaguchi S, Iza F, Jablonowski H, Klimova E, Kolb J, Krcma F, Lukes P, Machala Z, Marinov I, Mariotti D, Mededovic Thagard S, Minakata D, Neyts EC, Pawlat J, Petrovic ZL, Pflieger R, Reuter S, Schram DC, Schröter S, Shiraiwa M, Tarabová B, Tsai PA, Verlet JRR, von Woedtke T, Wilson KR, Yasui K, Zvereva G. Plasma–liquid interactions: a review and roadmap. ACTA ACUST UNITED AC 2016. [DOI: 10.1088/0963-0252/25/5/053002] [Citation(s) in RCA: 917] [Impact Index Per Article: 114.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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3
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Mächler L, Brennwald MS, Kipfer R. Membrane inlet mass spectrometer for the quasi-continuous on-site analysis of dissolved gases in groundwater. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2012; 46:8288-8296. [PMID: 22775356 DOI: 10.1021/es3004409] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We developed a stand-alone system based on a membrane inlet mass spectrometer (MIMS) for measuring dissolved gas concentrations in groundwater under field conditions. The system permits the concentrations of dissolved gases (He, Ar, Kr, N(2), and O(2)) in groundwater to be determined quasi-continuously (every 12 min) with a precision of better than 4% for He and Kr, and with a precision of 1% for Ar, N(2), and O(2) in air-saturated water. The detection limits are below 3 × 10(-9) cm(3)(STP)(g) for the noble gases and below 400 × 10(-9)cm(3)(STP)(g) for N(2) and O(2). The results of a first deployment of the system in the field indicate that changes in the concentration of Ar that result from diel fluctuations of 3°C in the river water temperature were still able to be resolved in groundwater, although the corresponding temperature signal almost vanished.
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Affiliation(s)
- Lars Mächler
- Department of Water Resources and Drinking Water, Eawag, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland.
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Fernandes SO, Michotey VD, Guasco S, Bonin PC, Bharathi PAL. Denitrification prevails over anammox in tropical mangrove sediments (Goa, India). MARINE ENVIRONMENTAL RESEARCH 2012; 74:9-19. [PMID: 22197479 DOI: 10.1016/j.marenvres.2011.11.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2010] [Revised: 07/26/2011] [Accepted: 11/08/2011] [Indexed: 05/31/2023]
Abstract
Denitrification, anammox (Anx) and di-nitrogen fixation were examined in two mangrove ecosystems- the anthropogenically influenced Divar and the relatively pristine Tuvem. Stratified sampling at 2 cm increments from 0 to 10 cm depth revealed denitrification as the main process of N₂ production in mangrove sediments. At Divar, denitrification was ∼3 times higher than at Tuvem with maximum activity of 224.51 ± 6.63 nmol N₂ g⁻¹ h⁻¹ at 0-2 cm. Denitrifying genes (nosZ) numbered up to 2 × 10⁷ copies g⁻¹ sediment and belonged to uncultured microorganisms clustering within Proteobacteria. Anammox was more prominent at deeper depths (8-10 cm) mainly in Divar with highest activity of 101.15 ± 87.73 nmol N₂ g⁻¹ h⁻¹ which was 5 times higher than at Tuvem. Di-nitrogen fixation was detected only at Tuvem with a maximum of 12.47 ± 8.36 nmol N₂ g⁻¹ h⁻¹. Thus, in these estuarine habitats prone to high nutrient input, N₂-fixation is minimal and denitrification rather than Anx serves as an important mechanism for counteracting N loading.
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Affiliation(s)
- Sheryl Oliveira Fernandes
- Marine Microbiology Laboratory, National Institute of Oceanography, CSIR, Dona Paula, Goa 403004, India
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5
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Schlüter M, Gentz T. Application of membrane inlet mass spectrometry for online and in situ analysis of methane in aquatic environments. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2008; 19:1395-1402. [PMID: 18789719 DOI: 10.1016/j.jasms.2008.07.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2008] [Revised: 07/15/2008] [Accepted: 07/15/2008] [Indexed: 05/26/2023]
Abstract
A method is presented for the online measurement of methane in aquatic environments by application of membrane inlet mass spectrometry (MIMS). For this purpose, the underwater mass spectrometer Inspectr200-200 was applied. A simple and reliable volumetric calibration technique, based on the mixing of two end member concentrations, was used for the analysis of CH(4) by MIMS. To minimize interferences caused by the high water vapor content, permeating through the membrane inlet system into the vacuum section of the mass spectrometer, a cool-trap was designed. With the application of the cool-trap, the detection limit was lowered from 100 to 16 nmol/L CH(4). This allows for measurements of methane concentrations in surface and bottom waters of coastal areas and lakes. Furthermore, in case of membrane rupture, the cool-trap acts as a security system, avoiding total damage of the mass spectrometer by flushing it with water. The Inspectr200-200 was applied for studies of methane and carbon dioxide concentrations in coastal areas of the Baltic Sea and Lake Constance. The low detection limit and fast response time of the MIMS allowed a detailed investigation of methane concentrations in the vicinity of gas seepages.
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Affiliation(s)
- Michael Schlüter
- Alfred-Wegener Institute for Polar and Marine Research, Bremerhaven, Germany.
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Degn H, Cox RP, Lloyd D. Continuous measurement of dissolved gases in biochemical systems with the quadrupole mass spectrometer. METHODS OF BIOCHEMICAL ANALYSIS 2006; 31:165-94. [PMID: 3927115 DOI: 10.1002/9780470110522.ch3] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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7
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Choi PS, Naal Z, Moore C, Casado-Rivera E, Abruña HD, Helmann JD, Shapleigh JP. Assessing the impact of denitrifier-produced nitric oxide on other bacteria. Appl Environ Microbiol 2006; 72:2200-5. [PMID: 16517672 PMCID: PMC1393196 DOI: 10.1128/aem.72.3.2200-2205.2006] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2005] [Accepted: 01/09/2006] [Indexed: 11/20/2022] Open
Abstract
A series of experiments was undertaken to learn more about the impact on other bacteria of nitric oxide (NO) produced during denitrification. The denitrifier Rhodobacter sphaeroides 2.4.3 was chosen as a denitrifier for these experiments. To learn more about NO production by this bacterium, NO levels during denitrification were measured by using differential mass spectrometry. This revealed that NO levels produced during nitrate respiration by this bacterium were in the low muM range. This concentration of NO is higher than that previously measured in denitrifiers, including Achromobacter cycloclastes and Paracoccus denitrificans. Therefore, both 2.4.3 and A. cycloclastes were used in this work to compare the effects of various NO levels on nondenitrifying bacteria. By use of bacterial overlays, it was found that the NO generated by A. cycloclastes and 2.4.3 cells during denitrification inhibited the growth of both Bacillus subtilis and R. sphaeroides 2.4.1 but that R. sphaeroides 2.4.3 caused larger zones of inhibition in the overlays than A. cycloclastes. Both R. sphaeroides 2.4.3 and A. cycloclastes induced the expression of the NO stress response gene hmp in B. subtilis. Taken together, these results indicate that there is variability in the NO concentrations produced by denitrifiers, but, irrespective of the NO levels produced, microbes in the surrounding environment were responsive to the NO produced during denitrification.
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Affiliation(s)
- Peter S Choi
- Cornell University, Department of Microbiology, Wing Hall, Ithaca, NY 14853, USA
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Lloyd D, Ralphs JR, Harris JC. Giardia intestinalis, a eukaryote without hydrogenosomes, produces hydrogen. MICROBIOLOGY (READING, ENGLAND) 2002; 148:727-733. [PMID: 11882707 DOI: 10.1099/00221287-148-3-727] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The microaerophilic flagellated protist Giardia intestinalis, the commonest protozoal agent of intestinal infections worldwide, is of uncertain phylogeny, but is usually regarded as the earliest branching of the eukaryotic clades. Under strictly anaerobic conditions, a mass spectrometric investigation of gas production indicated a low level of generation of dihydrogen (2 nmol x min(-1) per 10(7) organisms), about 10-fold lower than that in Trichomonas vaginalis under similar conditions. Hydrogen evolution was O2 sensitive, and inhibited by 100 microM metronidazole. Fluorescent labelling of G. intestinalis cells using monoclonal antibodies to typical hydrogenosomal enzymes from T. vaginalis (malate enzyme, and succinyl-CoA synthetase alpha and beta subunits), and to the large-granule fraction (hydrogenosome-enriched, also from T. vaginalis) gave no discrete localization of epitopes. Cell-free extracts prepared under anaerobic conditions showed the presence of a CO-sensitive hydrogenase activity. This first report of hydrogen production in a eukaryote with no recognizable hydrogenosomes raises further questions about the early branching status of G. intestinalis; the physiological characterization of its hydrogenase, and its recently elucidated gene sequence, will aid further phylogenetic investigations.
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Affiliation(s)
- David Lloyd
- Microbiology (BIOSI 1, Main Building), Cardiff University, PO Box 915, Cardiff CF10 3TL, Wales, UK1
| | - James R Ralphs
- Microbiology (BIOSI 1, Main Building), Cardiff University, PO Box 915, Cardiff CF10 3TL, Wales, UK1
| | - Janine C Harris
- Microbiology (BIOSI 1, Main Building), Cardiff University, PO Box 915, Cardiff CF10 3TL, Wales, UK1
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Lloyd D, Thomas KL, Cowie G, Tammam JD, Williams AG. Direct interface of chemistry to microbiological systems: membrane inlet mass spectrometry. J Microbiol Methods 2002; 48:289-302. [PMID: 11777577 DOI: 10.1016/s0167-7012(01)00331-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Direct measurement of dissolved gases and low molecular weight volatiles through permeable membranes (e.g. 50-microm-thick silicone rubber), provides an invaluable tool for the investigation of the activities of microorganisms in the laboratory and in their natural environments. Multiple molecular species are monitored at a single point. Fast response times (t(90%)<1 min) and long-term stability, (<1% week(-1)); high specificity and high sensitivity (e.g. 0.2 microM for O(2), <0.5 mM for ethanol), provides a technique that can provide information on the kinetics of processes over many decades (10(0)-10(6)) of minutes. Spatial resolution of <1 mm enables 3D mapping of gases in complex ecosystems (sediments, peat, soils, biofilms, foodstuffs). Results with membrane inlet mass spectrometry (MIMS) when used in conjunction with confocal scanning laser microscopy, provides a powerful approach to the analysis of kinetic and spatial aspects of natural environments. Examples discussed are peat cores and cheese.
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Affiliation(s)
- David Lloyd
- BIOSI 1 (Microbiology), Cardiff University, P.O. Box 915, Cardiff CF10 3TL, Wales, UK.
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Tammam JD, Williams AG, Banks J, Cowie G, Lloyd D. Membrane inlet mass spectrometric measurement of O2 and CO2 gradients in cultures of Lactobacillus paracasei and a developing Cheddar cheese ecosystem. Int J Food Microbiol 2001; 65:11-22. [PMID: 11322693 DOI: 10.1016/s0168-1605(00)00438-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Membrane inlet mass spectrometry was used to measure O2 and CO2 as depth profiles in stab cultures of 0.1% agar Man Rogosa Sharpe medium inoculated with Lactobacillus paracasei CI3. Diffusion of CO2 from the central column of growth into the medium was observed to show lower concentrations where bacteria were absent. CO2 profiles developed in a manner similar to those in Cheddar cheese and O2 was undetectable at similar depths. Gases were analysed in Cheddar cheese over a maturation period of 200 d. O2 was detectable to depths of 13, 6 and 2.5 mm on days 2, 9 and 15, respectively, but then became undetectable at depths of 2.5-3 mm. CO2 concentrations measured within the cheese increased 10-fold from day 2 to day 200 to reach a value of around 15 mM. The progress of measured CO2 concentration over time at a given depth in cheese shows a hyperbolic type increase. Coefficient of regression values increase with depth to a maximum value of R2 = 0.93. In both systems, reductions and increases in CO2 were due to the absence or presence of bacterial growth, respectively. Confocal scanning laser and scanning electron microscopy was used to show spatial heterogeneity of microcolonies within the cheese ecosystem. This information can potentially be used as a non-sensory evaluation of cheese maturity status. Measurement of gases in a cheese ecosystem provides the first description of mass spectrometry being used to monitor the processes of microbial gaseous exchange with respect to O2 and CO2 in a cheese ecosystem.
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Affiliation(s)
- J D Tammam
- School of Biosciences, Microbiology Group, Cardiff University, UK.
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11
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Firth JR, Edwards C. Effects of cultural conditions on denitrification by pseudomonas stutzeri measured by membrane inlet mass spectrometry. J Appl Microbiol 1999; 87:353-8. [PMID: 10540236 DOI: 10.1046/j.1365-2672.1999.00820.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Denitrification is a globally important process leading to loss of fertiliser efficiency and the production of the greenhouse gas nitrous oxide and nitric oxide, an ozone depleter. Membrane inlet mass spectrometry (MIMS) was employed to study the effect of different variables on the process of denitrification by Pseudomonas stutzeri in a defined salts medium. MIMS was used for concomitant measurements of nitrous oxide, nitrogen and oxygen and showed that denitrification occurred in the presence of dissolved oxygen. A nitrate concentration of 15 mmol l-1 and a nitrite concentration of 5 mmol l-1 were found to be optimum for complete denitrification of nitrate or nitrite to nitrogen and varying these concentrations had a marked effect on the ratio of gaseous products released. Denitrification products were also dependant on pH with neutral or alkaline conditions being best for production of gaseous end products. Our results suggest that under nutrient rich conditions the most important factor in the regulation of denitrification by Ps. stutzeri is the amount of nitrite generated at the first enzymatic stage of the process. This appears to cause inhibition of the denitrification pathway above 5 mmol l-1 and at high enough concentrations (15 mmol l-1) restricts growth.
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Biagini GA, McIntyre PS, Finlay BJ, Lloyd D. Carbohydrate and Amino Acid Fermentation in the Free-Living Primitive Protozoon Hexamita sp. Appl Environ Microbiol 1998; 64:203-7. [PMID: 16349480 PMCID: PMC124694 DOI: 10.1128/aem.64.1.203-207.1998] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/1997] [Accepted: 10/27/1997] [Indexed: 11/20/2022] Open
Abstract
Hexamita sp. is an amitochondriate free-living diplomonad which inhabits O(2)-limited environments, such as the deep waters and sediments of lakes and marine basins. C nuclear magnetic resonance spectroscopy reveals ethanol, lactate, acetate, and alanine as products of glucose fermentation under microaerobic conditions (23 to 34 muM O(2)). Propionic acid and butyric acid were also detected and are believed to be the result of fermentation of alternative substrates. Production of organic acids was greatest under microaerobic conditions (15 muM O(2)) and decreased under anaerobic (<0.25 muM O(2)) and aerobic (200 to 250 muM O(2)) conditions. Microaerobic incubation resulted in the production of high levels of oxidized end products (70% acetate) compared to that produced under anoxic conditions (20% acetate). In addition, data suggest that Hexamita cells contain the arginine dihydrolase pathway, generating energy from the catabolism of arginine to citrulline, ornithine, NH(4), and CO(2). The rate of arginine catabolism was higher under anoxic conditions than under microaerobic conditions. Hexamita cells were able to grow in the absence of a carbohydrate source, albeit with a lower growth rate and yield.
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Affiliation(s)
- G A Biagini
- Microbiology Group, School of Pure and Applied Biology, University of Wales College of Cardiff, Cardiff CF1 3TL, and School of Applied Sciences, University of Glamorgan, Pontypridd, Mid Glamorgan CF37 1DL, Wales, and Institute of Freshwater Ecology, Windermere Laboratory, The Ferry House, Ambleside, Cumbria LA22 OLP, United Kingdom
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Lloyd D, Thomas K, Price D, O'Neil B, Oliver K, Williams T. A membrane-inlet mass spectrometer miniprobe for the direct simultaneous measurement of multiple gas species with spatial resolution of 1 mm. J Microbiol Methods 1996. [DOI: 10.1016/0167-7012(96)00011-5] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Dornseiffer P, Meyer B, Heinzle E. Modeling of anaerobic formate kinetics in mixed biofilm culture using dynamic membrane mass spectrometric measurement. Biotechnol Bioeng 1995; 45:219-28. [DOI: 10.1002/bit.260450306] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Thomas KL, Lloyd D, Boddy L. Effects of oxygen, pH and nitrate concentration on denitrification by Pseudomonas species. FEMS Microbiol Lett 1994; 118:181-6. [PMID: 8013877 DOI: 10.1111/j.1574-6968.1994.tb06823.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The production of nitrogen-containing gases by denitrification in three organisms was examined using membrane inlet mass spectrometry. The effects of O2 (during both growth and maintenance) and of pH, nitrate concentration and carbon source were tested in non-proliferating cell suspensions. Two strains of Pseudomonas aeruginosa were capable of co-respiration of NO3- and O2 and, under controlled O2 supply, gave oscillatory denitrification. Variations in culture and assay conditions affected both the rate of denitrification and the ratio of end products (N2O:N2). Higher rates were seen following anaerobic growth. Optimum values of pH and nitrate concentration for denitrification are given. Generally, the optimum pH was 7.0-7.5, approximately that of the growth medium. Optimum nitrate concentration was generally 20 mM.
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Affiliation(s)
- K L Thomas
- Microbiology Group, School of Pure and Applied Biology, University of Wales College of Cardiff, UK
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Ellis JE, Wingfield JM, Cole D, Boreham PF, Lloyd D. Oxygen affinities of metronidazole-resistant and -sensitive stocks of Giardia intestinalis. Int J Parasitol 1993; 23:35-9. [PMID: 8468134 DOI: 10.1016/0020-7519(93)90095-g] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The common protozoon, Giardia intestinalis, parasitizes the upper small intestine of man, and is often refractory to treatment by metronidazole. Defective oxygen-scavenging mechanisms have been implicated as a cause of metronidazole resistance of another flagellate Trichomonas vaginalis, where metronidazole is also the most common drug treatment. Oxygen consumption of six clinical isolates of G. intestinalis and one line selected for resistance to metronidazole was measured over 0-50 microM-O2 using an oxygen electrode open for gas exchange. At > 30 microM-O2, inhibition of respiration was demonstrated in all seven stocks. Apparent oxygen affinities (KmO2) were found to range from 0.5 to 5.2 microM-O2; however, isolates from patients who failed to respond to treatment with metronidazole did not have measurably defective O2-scavenging capabilities compared with metronidazole-sensitive isolates. These strains did, however, show elevated NADPH-oxidase activities compared with metronidazole-sensitive strains. Results indicate that biochemical mechanisms of drug resistance in G. intestinalis may be quite different from those operating in T. vaginalis.
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Affiliation(s)
- J E Ellis
- School of Pure and Applied Biology, University of Wales College of Cardiff, Cardiff, U.K
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Paget TA, Kelly ML, Jarroll EL, Lindmark DG, Lloyd D. The effects of oxygen on fermentation in Giardia lamblia. Mol Biochem Parasitol 1993; 57:65-71. [PMID: 8093974 DOI: 10.1016/0166-6851(93)90244-r] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Detailed study of the effects of oxygen on the carbohydrate metabolism of Giardia lamblia revealed that low concentrations of oxygen (< 0.25 microM) produced profound alterations in the carbon balance of this organism. Although this concentration of oxygen could not be detected by mass spectrometry, a marked stimulation of ethanol production was observed. Associated with this was an inhibition of alanine production and oxidation of the intracellular NAD(P)H pool. Higher concentrations of oxygen inhibited ethanol production and further reduced levels of alanine. These results suggest that this stimulation is due to changes in carbon flux. Analysis of cell and medium hydrolysates after the growth of trophozoites in [U-14C]glucose suggests that G. lamblia does not synthesise detectable levels of labelled amino acids, except alanine and to a lesser extent valine, from this sugar. Trophozoites of G. lamblia have both glutamate dehydrogenase and alanine aminotransferase activity. As glutamate is taken up from the medium, it is suggested that glutamate dehydrogenase and alanine aminotransferase cooperate to convert pyruvate to alanine, with the concomitant oxidation of NAD(P)H.
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Affiliation(s)
- T A Paget
- Microbiology Group PABIO, University of Wales College of Cardiff, UK
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Lloyd D, Ellis JE, Hillman K, Williams AG. Membrane inlet mass spectrometry: probing the rumen ecosystem. SOCIETY FOR APPLIED BACTERIOLOGY SYMPOSIUM SERIES 1992; 21:155S-163S. [PMID: 1502598 DOI: 10.1111/j.1365-2672.1992.tb03635.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- D Lloyd
- Microbiology Group (PABIO), University of Wales College of Cardiff, UK
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Ellis JE, Cole D, Lloyd D. Influence of oxygen on the fermentative metabolism of metronidazole-sensitive and resistant strains of Trichomonas vaginalis. Mol Biochem Parasitol 1992; 56:79-88. [PMID: 1475004 DOI: 10.1016/0166-6851(92)90156-e] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The microaerophilic protozoon Trichomonas vaginals responds to extracellular changes in oxygen concentration: acetate, lactate, ethanol, H2 and CO2 formation, as well as glucose-depletion rates, are affected. All these variables except ethanol production rates, also differed between clinically metronidazole-sensitive (1910) and resistant (IR78 and CDC85) strains. Most interesting were the greatly increased glucose-scavenging rates of resistant isolates and their low specific activities of hydrogenase and H2 formation rates by comparison with the metronidazole-sensitive strain. Results suggest that all three strains of this parasite are well adapted to the O2 levels prevailing in situ (13-56 microM). Thus, vaginal oxygen tensions have more pronounced effects on the balances of fermentation products in the resistant strains, and results indicate that these strains may then use hydrogenosomal pathways to their advantage.
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Affiliation(s)
- J E Ellis
- Microbiology Group, School of Pure and Applied Biology, University of Wales College of Cardiff, UK
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Heinzle E. Present and potential applications of mass spectrometry for bioprocess research and control. J Biotechnol 1992; 25:81-114. [PMID: 1368465 DOI: 10.1016/0168-1656(92)90111-l] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
For on-line monitoring of bioprocesses present applications are mainly restricted to gas analysis, but several techniques have been improved recently: membrane probes, the application of MS/MS techniques, methods of correlating available on-line data like gas reaction rates with bioprocess characteristics using stoichiometric models and other empirical correlations. New ionization and ion separation methods for biomolecules are developing dramatically. Most striking developments in this area are improved desorption techniques, electrospray, the renaissance of time-of-flight instruments and new challenges in ion trap techniques. Enormous progress is made in the analysis of peptides and other biopolymers. Combinations with new separation techniques like capillary electrophoresis and capillary HPLC show new horizons in biomolecule analysis.
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Affiliation(s)
- E Heinzle
- Chemical Engineering Department, ETH Zürich, Switzerland
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Lloyd D, James CJ, Maitra PK. Mutations in phosphofructokinases alter the control characteristics of glycolysis in vivo in Saccharomyces cerevisiae. Yeast 1992; 8:291-301. [PMID: 1387501 DOI: 10.1002/yea.320080406] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Ethanol and CO2 production from glucose by non-proliferating suspensions of aerobically-grown, glucose-derepressed wild-type Saccharomyces cerevisiae is inhibited by O2; monitoring by mass spectrometry provides a direct method for measurement of the Pasteur effect. Under aerobic conditions, that part of the CO2 evolved equivalent to the O2 consumed, is produced by respiration: subtraction of this respiratory CO2 from the total gives CO2 produced by aerobic glycolysis. Pasteur quotients (anaerobic CO2/aerobic glycolytic CO2) were within the range 1.2 to 3.0. The Pasteur effect was not observed in the presence of carbonyl cyanide m-chlorophenylhydrazone, an uncoupler of mitochondrial energy metabolism, or in a rho degree cytoplasmic petite mutant. A 'non-allosteric' mutant with an altered regulatory subunit of phosphofructokinase showed no Pasteur effect. Strains bearing a nonsense mutation pfk1 in the catalytic subunit of soluble phosphofructokinase (PFKI) also showed no Pasteur effect; the residual fermentative activity of this strain was dependent on PFKII, the particulate phosphofructokinase. A double mutant lacking both PFKI and glucose-6-phosphate dehydrogenase showed similar characteristics to those of the single pfk1 mutant; this indicates that the hexose monophosphate shunt is not acting to bypass the phosphofructokinase block. A 'hyper-allosteric' mutant altered in the regulatory subunit encoded by the gene PFK2 showed characteristics of glucose fermentation and ethanol oxidation very similar to those of wild-type organisms. These results indicate that either of the two phosphofructokinases can carry out glycolysis.
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Affiliation(s)
- D Lloyd
- Microbiology Group (PABIO), University of Wales College of Cardiff, U.K
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Ellis JE, Mcintyre PS, Saleh M, Williams AG, Lloyd D. The influence of ruminal concentrations of O2 and CO2 on fermentative metabolism of the rumen entodiniomorphid ciliateEudiplodinium maggii. Curr Microbiol 1991. [DOI: 10.1007/bf02092025] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023]
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Lauritsen FR, Nielsen LT, Degn H, Lloyd D, Bohátka S. Identification of dissolved volatile metabolites in microbial cultures by membrane inlet tandem mass spectrometry. ACTA ACUST UNITED AC 1991. [DOI: 10.1002/bms.1200200504] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Paget TA, Raynor MH, Shipp DW, Lloyd D. Giardia lamblia produces alanine anaerobically but not in the presence of oxygen. Mol Biochem Parasitol 1990; 42:63-7. [PMID: 2122248 DOI: 10.1016/0166-6851(90)90113-z] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Proton nuclear magnetic resonance was used to follow glucose metabolism in Giardia lamblia. Under strictly anaerobic conditions this organism produces equimolar ethanol and alanine as well as CO2 and some acetate. Aerobically the production of both alanine and ethanol are inhibited and more acetate and CO2 are formed. These changes in the balance of products are reversible over the range 0-46 microM O2. In the presence of 46 microM O2, alanine was not detectable. The O2-sensitivity of alanine production may highlight the necessity for redox-balancing reactions in an organism exposed in situ to fluctuating concentrations of O2.
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Affiliation(s)
- T A Paget
- Microbiology Group, University of Wales College of Cardiff, U.K
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Paget TA, Lloyd D. Trichomonas vaginalis requires traces of oxygen and high concentrations of carbon dioxide for optimal growth. Mol Biochem Parasitol 1990; 41:65-72. [PMID: 2117256 DOI: 10.1016/0166-6851(90)90097-6] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The effects of O2 and CO2 on the growth in culture of Trichomonas vaginalis strain C1-NIH were investigated. Growth under pre-purified N2 in the absence of CO2 supplementation gave a doubling time of 4.4 h; when traces of O2 (less than 0.25 microM) were present, the doubling time was 3.5 h. Organisms grew most rapidly (doubling time 2.3 h) with traces of O2 (less than 0.25 microM) and with the CO2 level controlled at 5 mM. The balance of fermentation products from maltose was greatly influenced by supplied gases. Under strictly anaerobic conditions at 5 mM CO2, equimolar glycerol and lactate accounted for more than 95% of the measured products, whereas lower CO2 increased acetate production. Under microaerobic conditions (O2 less than 0.25 microM) acetate was the major product when CO2 was limited to that evolved endogenously; again 5 mM CO2 favoured glycerol and lactate production. Activities of key enzymes measured in cell-free extracts (pyruvate:ferredoxin oxidoreductase, hydrogenase, glycerol kinase, malate dehydrogenase (decarboxylating) and lactate dehydrogenase) altered with growth conditions commensurately with observed changes in metabolic flux patterns. These results suggest that T. vaginalis is optimally adapted to conditions it experiences in situ in the vagina (traces of O2, high CO2).
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Affiliation(s)
- T A Paget
- Microbiology Group (PABIO), University of Wales College of Cardiff, U.K
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Formate and glucose stimulation of methane and hydrogen production in rumen liquor. Curr Microbiol 1990. [DOI: 10.1007/bf02089419] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Lister AK, Wood KV, Cooks RG, Noon KR. Direct detection of organic compounds in water at parts-per-billion levels using a simple membrane probe and a quadrupole ion trap. ACTA ACUST UNITED AC 1989. [DOI: 10.1002/bms.1200181206] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Ellis JE, Williams AG, Lloyd D. Oxygen consumption by ruminal microorganisms: protozoal and bacterial contributions. Appl Environ Microbiol 1989; 55:2583-7. [PMID: 2513776 PMCID: PMC203126 DOI: 10.1128/aem.55.10.2583-2587.1989] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The relative contributions to O2 consumption made by the protozoal and bacterial populations present within the rumen were determined by using an open-type oxygen electrode system. Measurements indicated that two separate microbial populations contributed approximately equally to ruminal O2 consumption over the O2 concentration range experienced in situ (0.25 to 1.0 microM). The populations were observed to consume O2 under liquid-phase O2 concentrations of up to 7 microM, above which point rapid inactivation of O2 utilization was observed. Km values for the mixed population of bacteria and protozoa were 0.36 +/- 0.17 and 3.2 +/- 0.4 microM at concentrations of less than 1.6 and greater than 1.6 microM, respectively. O2 affinity values obtained for both the protozoal and bacterial populations were similar. O2 affinities of the isolated entodiniomorphid ciliates Polyplastron multivesiculatum and Eudiplodinium maggii showed O2 inhibition thresholds of 10 and 5, respectively, and apparent half-saturation constants (Km values) of 1.7 and 5.2 microM O2, respectively. Corresponding Vmax values were 7.8 microM O2 per min per 10(5) organisms for P. multivesiculatum and 3.6 microM O2 per min per 10(5) organisms for E. maggii. Mass spectroscopic analysis detected average rates of H2 production of 12.0 and 3.7 microM H2 per min per 10(5) organisms for P. multivesiculatum and E. maggii, respectively. Trace levels of dissolved O2 (less than 0.25 microM) stimulated the H2 production rate of E. maggii eightfold but inhibited that of P. multivesiculatum by 18%.
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Affiliation(s)
- J E Ellis
- Microbiology Group (PABIO), University of Wales College of Cardiff
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Abstract
Glucose-supported O2 uptake in the filarial nematode Brugia pahangi was partially inhibited by antimycin A (30-40%), with the remaining activity being sensitive to o-hydroxydiphenyl or salicylhydroxamic acid (SHAM). The production of CO2 by B. pahangi in the presence of D-glucose was stimulated by O2; the stimulation of CO2; the stimulation of CO2 production was sensitive to antimycin A. The O2 dependencies of respiration showed that the apparent O2 affinity for B. pahangi was diminished in the presence of antimycin A; O2 thresholds for inhibition of respiration were observed which showed that the alternative electron transport pathway was less sensitive to inhibition at elevated O2 concentrations. H2O2 production and its excretion could be detected in whole B. pahangi; higher rates were observed in the presence of the uncoupler carbonyl cyanide m-chlorophenylhydrazone. The effects of inhibitors on H2O2 production suggest two sites of H2O2 production, one associated with the classical antimycin A-sensitive pathway, the other with the alternative respiratory pathway. The similarity in the O2 dependencies of H2O2 production and respiration may indicate that H2O2 production is involved in O2-mediated toxicity. Succinate and malate respiring sub-mitochondrial particles of B. pahangi produced O2.- radicals at a site on the antimycin A-sensitive respiratory pathway. Inhibition of the alternative electron pathway by SHAM was unusual; sub-millimolar concentrations markedly stimulated respiration, H2O2 production and O2.- production by 30, 20 and 25%, respectively, whereas higher concentrations (greater than 2.5 mM) inhibited respiration by 75% and H2O2 and O2.- production by up to 85%.
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Lloyd D, Hillman K, Yarlett N, Williams AG. Hydrogen production by rumen holotrich protozoa: effects of oxygen and implications for metabolic control by in situ conditions. THE JOURNAL OF PROTOZOOLOGY 1989; 36:205-13. [PMID: 2657036 DOI: 10.1111/j.1550-7408.1989.tb01075.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Experiments with washed suspensions of holotrich protozoa (Isotricha spp. and Dasytricha ruminantium) showed that both organisms have an efficient O2-scavenging capability (apparent Km values 2.3 and 0.3 microM, respectively). Reversible inhibition of H2 production increased almost linearly with increasing O2 up to 1.5 microM; higher levels of O2 gave irreversible inhibition. In situ determinations of H2, CH4, O2 and CO2 in ovine rumen liquor, using a membrane inlet mass spectrometer probe, indicated that O2 was present before feeding at 1-1.5 microM and decreased to undetectable levels (less than 0.25 microM) within 25 min after feeding. A transient increase in O2 concentration after feeding occurred only in defaunated animals and resulted in suppression of CH4 and CO2 production. The presence of washed holotrich protozoa decreases the O2 sensitivity of CH4 production by suspensions of a cultured methanogenic bacterium Methanosarcina barkeri. It is concluded that holotrich protozoa play a role in ruminal O2 utilization as well as in the production of fermentation end products (especially short-chain volatile fatty acids) utilized by the ruminant and H2 utilized by methanogenic bacteria. These hydrogenosome-containing protozoa thus both control patterns of fermentation by influencing O2 levels, and are themselves regulated by the low ambient O2 concentrations they experience in the rumen.
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Affiliation(s)
- D Lloyd
- Department of Microbiology, University College, Cardiff, Wales, United Kingdom
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Hillman K, Lloyd D, Williams AG. Interactions between the methanogen Methanosarcina barkeri and rumen holotrich ciliate protozoa. Lett Appl Microbiol 1988. [DOI: 10.1111/j.1472-765x.1988.tb01250.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Lloyd D, Whitmore TN. Hydrogen-dependent control of the continuous thermophilic anaerobic digestion process using membrane inlet mass spectrometry. Lett Appl Microbiol 1988. [DOI: 10.1111/j.1472-765x.1988.tb01202.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Lloyd D, Boddy L, Davies KJ. Persistence of bacterial denitrification capacity under aerobic conditions: The rule rather than the exception. FEMS Microbiol Lett 1987. [DOI: 10.1111/j.1574-6968.1987.tb02354.x] [Citation(s) in RCA: 126] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Lloyd D, James C. The Pasteur effect in yeasts: Mass spectrometric monitoring of oxygen uptake, and carbon dioxide and ethanol production. FEMS Microbiol Lett 1987. [DOI: 10.1111/j.1574-6968.1987.tb02294.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Yarlett N, Rowlands C, Evans JC, Lloyd D. Respiration of the hydrogenosome-containing fungus Neocallimastix patriciarum. Arch Microbiol 1987. [DOI: 10.1007/bf00429642] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Yarlett N, Rowlands CC, Yarlett NC, Evans JC, Lloyd D. Reduction of niridazole by metronidazole resistant and susceptible strains of Trichomonas vaginalis. Parasitology 1987; 94 ( Pt 1):93-9. [PMID: 3029651 DOI: 10.1017/s0031182000053488] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The inhibitory effect of niridazole on hydrogen production by metronidazole-resistant (CDC-85) and susceptible (C1-NIH) Trichomonas vaginalis strains was investigated. The results show that niridazole is more effective than metronidazole in inhibiting hydrogen production by the resistant isolate. In CDC-85 aerobic inhibition requires a 4-fold increase in metronidazole concentration compared with that required anaerobically, but the corresponding factor for niridazole is only 1.5-fold. Reduction of the drug by a hydrogenosome-enriched preparation gave rise to a multiline electron spin resonance detectable signal, which is due to a nitrogen-centred radical.
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Yarlett N, Yarlett NC, Lloyd D. Ferredoxin-dependent reduction of nitroimidazole derivatives in drug-resistant and susceptible strains of Trichomonas vaginalis. Biochem Pharmacol 1986; 35:1703-8. [PMID: 3486660 DOI: 10.1016/0006-2952(86)90327-8] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The inhibitory effect of a range of nitroimidazole-derivatives on H2 production by metronidazole resistant (CDC-85) and susceptible (C1-NIH) Trichomonas vaginalis strains was investigated. The 2-, 4-, and 5-nitro-derivatives used had one-electron reduction potentials within the range -250 to -525 mV. Nitroimidazole concentrations giving 50% inhibition of H2 production (kiH2) for compounds with one-electron reduction potentials in the range -250 to -425 mV were found to be similar for both strains tested. Compounds with one-electron reduction potentials below -425 mV give 10-fold higher KiH2 values for the metronidazole resistant isolate. Both strains showed increased KiH2 for compounds with potentials lower than -500 mV. The addition of 2.1 kPa (0.02 atm) O2 to the gas phase resulted in increasing the kiH2 values for all the compounds tested, but had the greater effect on results obtained with the resistant isolate using nitroimidazoles in the range -425 to -490 mV. The results enable the proposal that the resistant isolate CDC-85 has a ferredoxin with altered redox properties or reduced intracellular levels.
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Yarlett N, Yarlett NC, Lloyd D. Metronidazole-resistant clinical isolates of Trichomonas vaginalis have lowered oxygen affinities. Mol Biochem Parasitol 1986; 19:111-6. [PMID: 3487729 DOI: 10.1016/0166-6851(86)90115-5] [Citation(s) in RCA: 66] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Oxygen affinities of metronidazole susceptible and resistant isolates of the parasitic flagellate protozoon Trichomonas vaginalis were determined by mass spectrometric methods. Apparent O2Km values for the respiration of non-proliferating cell suspensions were about 10-fold higher for metronidazole resistant strains than for the susceptible strains C1-NIH or NYH-286. Simultaneous monitoring of hydrogen evolution in the presence of increasing O2 tensions enabled apparent Ki values for H2 to be determined; and this function was independent of metronidazole susceptibility. Apparent O2 affinities of the hydrogenosomal and non-sedimentable fractions were determined for the strains CDC 85 (metronidazole resistant) and C1-NIH, which showed the deficiency in the O2 scavenging capacity by the resistant strain to be associated with the hydrogenosome-containing fraction.
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Lloyd D, Davies KJ, Boddy L. Mass spectrometry as en ecological tool for in situ measurement of dissolved gases in sediment systems. FEMS Microbiol Lett 1986. [DOI: 10.1111/j.1574-6968.1986.tb01933.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Lloyd D, Yarlett N, Yarlett NC. Inhibition of hydrogen production in drug-resistant and susceptible Trichomonas vaginalis strains by a range of nitroimidazole derivatives. Biochem Pharmacol 1986; 35:61-4. [PMID: 3000386 DOI: 10.1016/0006-2952(86)90556-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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Lloyd D, Bohátka S, Szilágyi J. Quadrupole mass spectrometry in the monitoring and control of fermentations. BIOSENSORS-BASEL 1985. [DOI: 10.1016/0265-928x(85)80003-1] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Lloyd D, Scott RI, Williams T. Membrane inlet mass spectrometry — measurement of dissolved gases in fermentation liquids. Trends Biotechnol 1983. [DOI: 10.1016/0167-7799(83)90071-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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