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Oxygen levels are key to understanding "Anaerobic" protozoan pathogens with micro-aerophilic lifestyles. Adv Microb Physiol 2021; 79:163-240. [PMID: 34836611 DOI: 10.1016/bs.ampbs.2021.09.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Publications abound on the physiology, biochemistry and molecular biology of "anaerobic" protozoal parasites as usually grown under "anaerobic" culture conditions. The media routinely used are poised at low redox potentials using techniques that remove O2 to "undetectable" levels in sealed containers. However there is growing understanding that these culture conditions do not faithfully resemble the O2 environments these organisms inhabit. Here we review for protists lacking oxidative energy metabolism, the oxygen cascade from atmospheric to intracellular concentrations and relevant methods of measurements of O2, some well-studied parasitic or symbiotic protozoan lifestyles, their homeodynamic metabolic and redox balances, organism-drug-oxygen interactions, and the present and future prospects for improved drugs and treatment regimes.
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Lloyd D, Millet CO, Williams CF, Hayes AJ, Pope SJA, Pope I, Borri P, Langbein W, Olsen LF, Isaacs MD, Lunding A. Functional imaging of a model unicell: Spironucleus vortens as an anaerobic but aerotolerant flagellated protist. Adv Microb Physiol 2020; 76:41-79. [PMID: 32408947 DOI: 10.1016/bs.ampbs.2020.01.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Advances in optical microscopy are continually narrowing the chasm in our appreciation of biological organization between the molecular and cellular levels, but many practical problems are still limiting. Observation is always limited by the rapid dynamics of ultrastructural modifications of intracellular components, and often by cell motility: imaging of the unicellular protist parasite of ornamental fish, Spironucleus vortens, has proved challenging. Autofluorescence of nicotinamide nucleotides and flavins in the 400-580 nm region of the visible spectrum, is the most useful indicator of cellular redox state and hence vitality. Fluorophores emitting in the red or near-infrared (i.e., phosphors) are less damaging and more penetrative than many routinely employed fluors. Mountants containing free radical scavengers minimize fluorophore photobleaching. Two-photon excitation provides a small focal spot, increased penetration, minimizes photon scattering and enables extended observations. Use of quantum dots clarifies the competition between endosomal uptake and exosomal extrusion. Rapid motility (161 μm/s) of the organism makes high resolution of ultrastructure difficult even at high scan speeds. Use of voltage-sensitive dyes determining transmembrane potentials of plasma membrane and hydrogenosomes (modified mitochondria) is also hindered by intracellular motion and controlled anesthesia perturbs membrane organization. Specificity of luminophore binding is always questionable; e.g. cationic lipophilic species widely used to measure membrane potentials also enter membrane-bounded neutral lipid droplet-filled organelles. This appears to be the case in S. vortens, where Coherent Anti-Stokes Raman Scattering (CARS) micro-spectroscopy unequivocally images the latter and simultaneous provides spectral identification at 2840 cm-1. Secondary Harmonic Generation highlights the highly ordered structure of the flagella.
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Affiliation(s)
- David Lloyd
- School of Biosciences, Cardiff University, Cardiff, Wales, United Kingdom; School of Engineering, Cardiff, Wales, United Kingdom
| | - Coralie O Millet
- School of Biosciences, Cardiff University, Cardiff, Wales, United Kingdom
| | | | - Anthony J Hayes
- School of Biosciences, Cardiff University, Cardiff, Wales, United Kingdom
| | - Simon J A Pope
- School of Chemistry, Main Building, Cardiff University, Cardiff, Wales, United Kingdom
| | - Iestyn Pope
- School of Biosciences, Cardiff University, Cardiff, Wales, United Kingdom
| | - Paola Borri
- School of Biosciences, Cardiff University, Cardiff, Wales, United Kingdom
| | - Wolfgang Langbein
- School of Physics and Astronomy, Cardiff University, Cardiff, Wales, United Kingdom
| | - Lars Folke Olsen
- Biochemistry and Molecular Biology, University of Southern Denmark, Odense M, Denmark
| | - Marc D Isaacs
- School of Biosciences, Cardiff University, Cardiff, Wales, United Kingdom
| | - Anita Lunding
- Biochemistry and Molecular Biology, University of Southern Denmark, Odense M, Denmark
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Response of Anaerobic Protozoa to Oxygen Tension in Anaerobic System. Int Microbiol 2019; 22:355-361. [PMID: 30811001 DOI: 10.1007/s10123-019-00058-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Revised: 01/04/2019] [Accepted: 01/04/2019] [Indexed: 10/27/2022]
Abstract
The effect of oxygen on anaerobic protozoa was studied in anaerobic batch reactors inoculated with sludge and protozoa cultures. Among the protozoa genera, Metopus, Brachonella, Plagiopyla, Trepomonas, and Vanella were more sensitive to oxygen compared to other genera. Protozoa genera Menoidium, Rhynchomonas, Cyclidium, Spathidium, and Amoeba were found to survive under aerobic conditions, and the growth rate was slightly higher or similar to anaerobic condition. O2 tension resulted in the loss of free and endosymbiotic methanogens in anaerobic system, while methanogens were observed inside the protozoan cysts. Survival of anaerobic protozoa declined considerably when the O2 tension exceeded 1% atm. sat. and showed chemosensory behavior in response to O2 exposure. Superoxide dismutase activity was detected in survived protozoa cells under O2 tension. Facultative anaerobic protozoa with SOD activity can provide a mechanism to overcome possible occurrence of oxygen toxicity in the treatment of wastewater in anaerobic reactor.
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Antioxidant defences of Spironucleus vortens: Glutathione is the major non-protein thiol. Mol Biochem Parasitol 2014; 196:45-52. [DOI: 10.1016/j.molbiopara.2014.07.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Revised: 07/21/2014] [Accepted: 07/28/2014] [Indexed: 11/17/2022]
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Oxygen tolerance and occurrence of superoxide dismutase as an antioxidant enzyme in Metopus es. Res Microbiol 2010; 161:227-33. [PMID: 20146936 DOI: 10.1016/j.resmic.2010.01.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2009] [Revised: 01/25/2010] [Accepted: 01/26/2010] [Indexed: 11/18/2022]
Abstract
The free-living anaerobic ciliate Metopus es was found to possess moderate tolerance to oxygen. Direct oxygen exposure led to the death of >80% of the population within 24h, but the remaining cells exhibited some oxygen tolerance and survived up to 4 days without any growth. Survival of the ciliate was observed only in an oxygen tension up to 7.0microM, and higher O(2) concentrations (>7.0microM) were found to be detrimental with a K(m) value of 3.5microM. The percentage of survival (50%) was higher when the culture was exposed to a low oxygen level (1.3microM) and it decreased with increasing oxygen tension. No catalase activity was detected in the extract of surviving ciliates. Maximum superoxide dismutase (SOD) activity of 1.52+/-0.4U/mg protein was observed at 1.3microM oxygen. SOD activity was not affected by cyanide or hydrogen peroxide, indicating that it belongs to the Mn type of SOD. Methanogenic endosymbionts in M. es lost their autofluorescence on oxygen exposure of >5.0microM, but their viability was not permanently affected, as indicated by the maintenance of a similar number of methanogens/cell upon restoring the anaerobic condition.
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Lloyd D, Harris JC, Biagini GA, Hughes MR, Maroulis S, Bernard C, Wadley RB, Edwards MR. The plasma membrane of microaerophilic protists: oxidative and nitrosative stress. Microbiology (Reading) 2004; 150:1183-1190. [PMID: 15133079 DOI: 10.1099/mic.0.26834-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The trans-plasma-membrane electrochemical potential of microaerophilic protists was monitored by the use of voltage-sensitive charged lipophilic fluorophores; of the many available probes, the anionic oxonol dye bis(1,3-dibarbituric acid)-trimethine oxonol [DiBAC4(3)] is an example of one which has been successfully employed using fluorescence microscopy, confocal laser-scanning microscopy and flow cytometry. Several microaerophilic protists have been investigated with this dye; these were Giardia intestinalis, Trichomonas vaginalis, Tritrichomonas foetus, Hexamita inflata and Mastigamoeba punctachora. Under conditions where they exhibit normal vitality, these organisms exclude DiBAC4(3) by virtue of their maintenance of a plasma-membrane potential (negative inside). Uptake of the fluorophore is indicative of disturbance to this membrane (i.e. by inhibition of pump/leak balance, blockage of channels or generation of ionic leaks), and is indicative of metabolic perturbation or environmental stress. Here, it is shown that oxidative or nitrosative stress depolarizes the plasma membranes of the aforementioned O2-sensitive organisms and allows DiBAC4(3) influx. Oxonol uptake thereby provides a sensitive and early indication of plasma-membrane perturbation by agents that may lead to cytotoxicity and eventually to cell death by necrotic or apoptotic pathways.
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Affiliation(s)
- D Lloyd
- Microbiology (BIOSI 1) Main Building, Cardiff University, PO Box 915, Cardiff CF10 3TL, UK
| | - J C Harris
- Microbiology (BIOSI 1) Main Building, Cardiff University, PO Box 915, Cardiff CF10 3TL, UK
| | - G A Biagini
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, 2052, Australia
| | - M R Hughes
- Department of Chemistry, King's College University of London, Strand, London WC2R 2LS, UK
| | - S Maroulis
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, 2052, Australia
| | - C Bernard
- School of Science, Parramatta Campus, University of Western Sydney, Australia
| | - R B Wadley
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, 2052, Australia
| | - M R Edwards
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, 2052, Australia
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Lloyd D. Noninvasive methods for the investigation of organisms at low oxygen levels. ADVANCES IN APPLIED MICROBIOLOGY 2003; 51:155-83. [PMID: 12236057 DOI: 10.1016/s0065-2164(02)51005-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- David Lloyd
- School of Biosciences (Microbiology), Main Building, Cardiff University, P. O. Box 915, Cardiff CF10 3TL, Wales, United Kingdom
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Lloyd D, Harris JC, Maroulis S, Wadley R, Ralphs JR, Hann AC, Turner MP, Edwards MR. The "primitive" microaerophile Giardia intestinalis (syn. lamblia, duodenalis) has specialized membranes with electron transport and membrane-potential-generating functions. MICROBIOLOGY (READING, ENGLAND) 2002; 148:1349-1354. [PMID: 11988508 DOI: 10.1099/00221287-148-5-1349] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Here it is shown that the flagellated protozoon Giardia intestinalis, commonly regarded as an early branching eukaryote because of its lack of mitochondria, has membraneous structures that partition the cationic, membrane-potential-sensitive fluorophore rhodamine 123. This organism also reduces a tetrazolium fluorogen at discrete plasma-membrane-associated sites. That these functions occur in distinctive specialized membrane systems supports the growing evidence that G. intestinalis may not be primitive, but is derived from an aerobic, mitochondria-containing flagellate.
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Affiliation(s)
- David Lloyd
- School of Biosciences (Microbiology), Cardiff University, PO Box 915, Cardiff CF10 3TL, Wales, UK1
| | - Janine C Harris
- School of Biosciences (Microbiology), Cardiff University, PO Box 915, Cardiff CF10 3TL, Wales, UK1
| | - Sarah Maroulis
- Department of Biochemistry and Molecular Genetics2 and Cellular Analysis Facility, Department of Microbiology and Immunology3, University of New South Wales, Sydney 2052, Australia
| | - Ron Wadley
- Department of Biochemistry and Molecular Genetics2 and Cellular Analysis Facility, Department of Microbiology and Immunology3, University of New South Wales, Sydney 2052, Australia
| | - James R Ralphs
- School of Biosciences (Microbiology), Cardiff University, PO Box 915, Cardiff CF10 3TL, Wales, UK1
| | - Ao C Hann
- School of Biosciences (Microbiology), Cardiff University, PO Box 915, Cardiff CF10 3TL, Wales, UK1
| | - Michael P Turner
- School of Biosciences (Microbiology), Cardiff University, PO Box 915, Cardiff CF10 3TL, Wales, UK1
| | - Michael R Edwards
- Department of Biochemistry and Molecular Genetics2 and Cellular Analysis Facility, Department of Microbiology and Immunology3, University of New South Wales, Sydney 2052, Australia
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Biagini GA, Park JH, Lloyd D, Edwards MR. The antioxidant potential of pyruvate in the amitochondriate diplomonads Giardia intestinalis and Hexamita inflata. MICROBIOLOGY (READING, ENGLAND) 2001; 147:3359-65. [PMID: 11739768 DOI: 10.1099/00221287-147-12-3359] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Giardia intestinalis and Hexamita inflata are microaerophilic protozoa which rely on fermentative metabolism for energy generation. These organisms have developed a number of antioxidant defence strategies to cope with elevated O(2) tensions which are inimical to survival. In this study, the ability of pyruvate, a central component of their energy metabolism, to act as a physiological antioxidant was investigated. The intracellular pools of 2-oxo acids in G. intestinalis were determined by HPLC. With the aid of a dichlorodihydrofluorescein diacetate-based assay, intracellular reactive oxygen species generation by G. intestinalis and H. inflata suspensions was monitored on-line. Addition of physiologically relevant concentrations of pyruvate to G. intestinalis and H. inflata cell suspensions was shown to attenuate the rate of H(2)O(2)- and menadione-induced generation of reactive oxygen species. In addition, pyruvate was also shown to decrease the generation of low-level chemiluminescence arising from the oxygenation of anaerobic suspensions of H. inflata. In contrast, addition of pyruvate to suspensions of respiring Saccharomyces cerevisiae was shown to increase the generation of reactive oxygen species. These data suggest that (i) in G. intestinalis and H. inflata, pyruvate exerts antioxidant activity at physiological levels, and (ii) it is the absence of a respiratory chain in the diplomonads which facilitates the observed antioxidant activity.
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Affiliation(s)
- G A Biagini
- School of Biochemistry and Molecular Genetics, University of New South Wales, Sydney 2052, Australia.
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Dimopoulos M, Bagnara AS, Edwards MR. Characterisation and sequence analysis of a carbamate kinase gene from the diplomonad Hexamita inflata. J Eukaryot Microbiol 2000; 47:499-503. [PMID: 11001147 DOI: 10.1111/j.1550-7408.2000.tb00081.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Hexamita inflata can derive energy from the degradation of arginine via the arginine dihydrolase pathway. Carbamate kinase catalyses the third enzymatic step of the pathway synthesising ATP from the catabolism of carbamyl phosphate. This study reports the identification and characterisation of a carbamate kinase gene from this free-living diplomonad, together with measurements of carbamate kinase enzyme activity in cell-free extracts and a preliminary analysis of the carbamate kinase mRNA by reverse-transcription polymerase chain reaction. Analysis of the carbamate kinase gene revealed the use of non-canonical codons for glutamine. Phylogenetic studies showed a consistent close relationship between carbamate kinase sequences of H. inflata and Giardia intestinalis.
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Affiliation(s)
- M Dimopoulos
- School of Biochemistry and Molecular Genetics, University of New South Wales, Sydney, Australia
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Biagini GA, Kirk K, Schofield PJ, Edwards MR. Role of K+ and amino acids in osmoregulation by the free-living microaerophilic protozoon Hexamita inflata. MICROBIOLOGY (READING, ENGLAND) 2000; 146 ( Pt 2):427-433. [PMID: 10708381 DOI: 10.1099/00221287-146-2-427] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The primitive free-living protozoon Hexamita inflata was found to maintain a cell volume of approximately 260 fI under standard culture conditions. On increasing the extracellular osmolality the volume decreased and the cells remained shrunken for >30 min. By contrast, a decrease in the external osmolality resulted in a transient increase in cell volume which was followed by an efficient 'regulatory volume decrease' (RVD). H. inflata contains high concentrations of amino acids, with alanine constituting over 70% of the total amino acid pool. Exposure to hypo-osmotic medium resulted in the loss from the cell of both amino acids and K+, via one or more swelling-activated pathways. The efflux of amino acids and K+, together with a charge-balancing counter-anion, accounted almost fully for the observed RVD. The pharmacological properties of the swelling-activated pathways differ from those of volume-sensitive transporters and channels described previously in other cell types.
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Affiliation(s)
- Giancarlo A Biagini
- School of Biochemistry and Molecular Biology, University of New South Wales, Sydney, NSW 2052, Australia1
| | - Kiaran Kirk
- Division of Biochemistry and Molecular Biology, Australian National University, Canberra, ACT 0200, Australia2
| | - Phillip J Schofield
- School of Biochemistry and Molecular Biology, University of New South Wales, Sydney, NSW 2052, Australia1
| | - Michael R Edwards
- School of Biochemistry and Molecular Biology, University of New South Wales, Sydney, NSW 2052, Australia1
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Affiliation(s)
- David Lloyd
- Microbiology Group, School of Biosciences, Cardiff University of Wales, PO Box 915, Cardiff CF1 3TL, UK
| | - Giancarlo A Biagini
- Microbiology Group, School of Biosciences, Cardiff University of Wales, PO Box 915, Cardiff CF1 3TL, UK
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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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