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Jin Y, Xiong W, Liu D, Wu Z, Xiao G, Wang S, Su H. Responses of straw foam-based aerobic granular sludge to atrazine: Insights from metagenomics and microbial community variations. CHEMOSPHERE 2023; 331:138828. [PMID: 37137392 DOI: 10.1016/j.chemosphere.2023.138828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 04/26/2023] [Accepted: 04/29/2023] [Indexed: 05/05/2023]
Abstract
Atrazine (ATZ) has caused serious environmental pollution, but the biodegradation of ATZ is relatively slow and inefficient. Herein, a straw foam-based aerobic granular sludge (SF-AGS) was developed, the spatially ordered architectures of which could greatly improve the drug tolerance and biodegradation efficiency of ATZ. The results showed that, in the presence of ATZ, chemical oxygen demand (COD), ammonium nitrogen (NH4+-N), total phosphorus (TP), and total nitrogen (TN) were effectively removed within 6 h, and the removal efficiencies were as high as 93.37%, 85.33%, 84.7%, and 70%, respectively. Furthermore, ATZ stimulated microbial consortia to secrete three times more extracellular polymers compared to without ATZ. Illumina MiSeq sequencing results showed that bacterial diversity and richness decreased, leading to significant changes in microbial population structure and composition. ATZ-resistant bacteria including Proteobacteria, Actinobacteria, and Burkholderia laid the biological basis for the stability of aerobic particles, efficient removal of pollutants, and degradation of ATZ. The study demonstrated that SF-AGS is feasible for ATZ-laden low-strength wastewater treatment.
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Affiliation(s)
- Yu Jin
- Beijing Key Laboratory of Bioprocess, and Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing, 100029, People's Republic of China
| | - Wei Xiong
- Beijing Key Laboratory of Bioprocess, and Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing, 100029, People's Republic of China
| | - Dan Liu
- Beijing Key Laboratory of Bioprocess, and Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing, 100029, People's Republic of China
| | - Zhiqing Wu
- Beijing Key Laboratory of Bioprocess, and Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing, 100029, People's Republic of China
| | - Gang Xiao
- Beijing Key Laboratory of Bioprocess, and Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing, 100029, People's Republic of China
| | - Shaojie Wang
- Beijing Key Laboratory of Bioprocess, and Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing, 100029, People's Republic of China.
| | - Haijia Su
- Beijing Key Laboratory of Bioprocess, and Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing, 100029, People's Republic of China.
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2
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Charles CJ, Rout SP, Jackson BR, Boxall SA, Akbar S, Humphreys PN. The evolution of alkaliphilic biofilm communities in response to extreme alkaline pH values. Microbiologyopen 2022; 11:e1309. [PMID: 36031955 PMCID: PMC9380404 DOI: 10.1002/mbo3.1309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 07/26/2022] [Accepted: 07/26/2022] [Indexed: 11/25/2022] Open
Abstract
Extremes of pH present a challenge to microbial life and our understanding of survival strategies for microbial consortia, particularly at high pH, remains limited. The utilization of extracellular polymeric substances within complex biofilms allows micro‐organisms to obtain a greater level of control over their immediate environment. This manipulation of the immediate environment may confer a survival advantage in adverse conditions to biofilms. Within the present study alkaliphilic biofilms were created at pH 11.0, 12.0, or 13.0 from an existing alkaliphilic community. In each pH system, the biofilm matrix provided pH buffering, with the internal pH being 1.0–1.5 pH units lower than the aqueous environment. Increasing pH resulted in a reduced removal of substrate and standing biomass associated with the biofilm. At the highest pH investigated (pH 13.0), the biofilms matrix contained a greater degree of eDNA and the microbial community was dominated by Dietzia sp. and Anaerobranca sp.
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Affiliation(s)
- Christopher J. Charles
- Department of Biological and Geographical Sciences, School of Applied SciencesUniversity of HuddersfieldHuddersfieldUK
- Present address:
Sulaimani Polytechnic UniversitySulaimaniIraq
| | - Simon P. Rout
- Department of Biological and Geographical Sciences, School of Applied SciencesUniversity of HuddersfieldHuddersfieldUK
| | - Brian R. Jackson
- Genesis BiosciencesUnit P1Capital Business Park, Capital PointParkwayCardiffUK
| | - Sally A. Boxall
- Genesis BiosciencesUnit P1Capital Business Park, Capital PointParkwayCardiffUK
| | - Sirwan Akbar
- Bio‐imaging Facility, School of Molecular and Cellular BiologyFaculty of Biological Sciences, University of LeedsLeedsUK
| | - Paul N. Humphreys
- Department of Biological and Geographical Sciences, School of Applied SciencesUniversity of HuddersfieldHuddersfieldUK
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3
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Predicting degradation of organic molecules in cementitious media. PROGRESS IN NUCLEAR ENERGY 2021. [DOI: 10.1016/j.pnucene.2021.103888] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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4
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Byrd N, Lloyd JR, Small JS, Taylor F, Bagshaw H, Boothman C, Morris K. Microbial Degradation of Citric Acid in Low Level Radioactive Waste Disposal: Impact on Biomineralization Reactions. Front Microbiol 2021; 12:565855. [PMID: 33995289 PMCID: PMC8114274 DOI: 10.3389/fmicb.2021.565855] [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: 11/20/2020] [Accepted: 03/10/2021] [Indexed: 11/18/2022] Open
Abstract
Organic complexants are present in some radioactive wastes and can challenge waste disposal as they may enhance subsurface mobility of radionuclides and contaminant species via chelation. The principal sources of organic complexing agents in low level radioactive wastes (LLW) originate from chemical decontamination activities. Polycarboxylic organic decontaminants such as citric and oxalic acid are of interest as currently there is a paucity of data on their biodegradation at high pH and under disposal conditions. This work explores the biogeochemical fate of citric acid, a model decontaminant, under high pH anaerobic conditions relevant to disposal of LLW in cementitious disposal environments. Anaerobic microcosm experiments were set up, using a high pH adapted microbial inoculum from a well characterized environmental site, to explore biodegradation of citrate under representative repository conditions. Experiments were initiated at three different pH values (10, 11, and 12) and citrate was supplied as the electron donor and carbon source, under fermentative, nitrate-, Fe(III)- and sulfate- reducing conditions. Results showed that citrate was oxidized using nitrate or Fe(III) as the electron acceptor at > pH 11. Citrate was fully degraded and removed from solution in the nitrate reducing system at pH 10 and pH 11. Here, the microcosm pH decreased as protons were generated during citrate oxidation. In the Fe(III)-reducing systems, the citrate removal rate was slower than in the nitrate reducing systems. This was presumably as Fe(III)-reduction consumes fewer moles of citrate than nitrate reduction for the same molar concentrations of electron acceptor. The pH did not change significantly in the Fe(III)-reducing systems. Sulfate reduction only occurred in a single microcosm at pH 10. Here, citrate was fully removed from solution, alongside ingrowth of acetate and formate, likely fermentation products. The acetate and lactate were subsequently used as electron donors during sulfate-reduction and there was an associated decrease in solution pH. Interestingly, in the Fe(III) reducing experiments, Fe(II) ingrowth was observed at pH values recorded up to 11.7. Here, TEM analysis of the resultant solid Fe-phase indicated that nanocrystalline magnetite formed as an end product of Fe(III)-reduction under these extreme conditions. PCR-based high-throughput 16S rRNA gene sequencing revealed that bacteria capable of nitrate Fe(III) and sulfate reduction became enriched in the relevant, biologically active systems. In addition, some fermentative organisms were identified in the Fe(III)- and sulfate-reducing systems. The microbial communities present were consistent with expectations based on the geochemical data. These results are important to improve long-term environmental safety case development for cementitious LLW waste disposal.
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Affiliation(s)
- Natalie Byrd
- Department of Earth and Environmental Sciences, Research Centre for Radwaste Disposal and Williamson Research Centre, The University of Manchester, Manchester, United Kingdom
| | - Jonathan R Lloyd
- Department of Earth and Environmental Sciences, Research Centre for Radwaste Disposal and Williamson Research Centre, The University of Manchester, Manchester, United Kingdom
| | - Joe S Small
- Department of Earth and Environmental Sciences, Research Centre for Radwaste Disposal and Williamson Research Centre, The University of Manchester, Manchester, United Kingdom.,National Nuclear Laboratory, Warrington, United Kingdom
| | - Frank Taylor
- Low Level Waste Repository Ltd., Seascale, United Kingdom
| | - Heath Bagshaw
- School of Engineering, The University of Liverpool, Liverpool, United Kingdom
| | - Christopher Boothman
- Department of Earth and Environmental Sciences, Research Centre for Radwaste Disposal and Williamson Research Centre, The University of Manchester, Manchester, United Kingdom
| | - Katherine Morris
- Department of Earth and Environmental Sciences, Research Centre for Radwaste Disposal and Williamson Research Centre, The University of Manchester, Manchester, United Kingdom
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5
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Wormald RM, Rout SP, Mayes W, Gomes H, Humphreys PN. Hydrogenotrophic Methanogenesis Under Alkaline Conditions. Front Microbiol 2020; 11:614227. [PMID: 33343555 PMCID: PMC7744349 DOI: 10.3389/fmicb.2020.614227] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Accepted: 11/11/2020] [Indexed: 01/04/2023] Open
Abstract
A cement-based geological disposal facility (GDF) is one potential option for the disposal of intermediate level radioactive wastes. The presence of both organic and metallic materials within a GDF provides the opportunity for both acetoclastic and hydrogenotrophic methanogenesis. However, for these processes to proceed, they need to adapt to the alkaline environment generated by the cementitious materials employed in backfilling and construction. Within the present study, a range of alkaline and neutral pH sediments were investigated to determine the upper pH limit and the preferred route of methane generation. In all cases, the acetoclastic route did not proceed above pH 9.0, and the hydrogenotrophic route dominated methane generation under alkaline conditions. In some alkaline sediments, acetate metabolism was coupled to hydrogenotrophic methanogenesis via syntrophic acetate oxidation, which was confirmed through inhibition studies employing fluoromethane. The absence of acetoclastic methanogenesis at alkaline pH values (>pH 9.0) is attributed to the dominance of the acetate anion over the uncharged, undissociated acid. Under these conditions, acetoclastic methanogens require an active transport system to access their substrate. The data indicate that hydrogenotrophic methanogenesis is the dominant methanogenic pathway under alkaline conditions (>pH 9.0).
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Affiliation(s)
- Richard M Wormald
- Department of Biological and Geographical Sciences, University of Huddersfield, Huddersfield, United Kingdom
| | - Simon P Rout
- Department of Biological and Geographical Sciences, University of Huddersfield, Huddersfield, United Kingdom
| | - William Mayes
- Department of Geography, Geology and Environment, University of Hull, Hull, United Kingdom
| | - Helena Gomes
- Department of Geography, Geology and Environment, University of Hull, Hull, United Kingdom.,Food, Water, Waste Research Group, Faculty of Engineering, University of Nottingham, Nottingham, United Kingdom
| | - Paul N Humphreys
- Department of Biological and Geographical Sciences, University of Huddersfield, Huddersfield, United Kingdom
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6
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Bassil NM, Small JS, Lloyd JR. Enhanced microbial degradation of irradiated cellulose under hyperalkaline conditions. FEMS Microbiol Ecol 2020; 96:fiaa102. [PMID: 32459307 PMCID: PMC7329180 DOI: 10.1093/femsec/fiaa102] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 05/25/2020] [Indexed: 01/04/2023] Open
Abstract
Intermediate-level radioactive waste includes cellulosic materials, which under the hyperalkaline conditions expected in a cementitious geological disposal facility (GDF) will undergo abiotic hydrolysis forming a variety of soluble organic species. Isosaccharinic acid (ISA) is a notable hydrolysis product, being a strong metal complexant that may enhance the transport of radionuclides to the biosphere. This study showed that irradiation with 1 MGy of γ-radiation under hyperalkaline conditions enhanced the rate of ISA production from the alkali hydrolysis of cellulose, indicating that radionuclide mobilisation to the biosphere may occur faster than previously anticipated. However, irradiation also made the cellulose fibres more available for microbial degradation and fermentation of the degradation products, producing acidity that inhibited ISA production via alkali hydrolysis. The production of hydrogen gas as a fermentation product was noted, and this was associated with a substantial increase in the relative abundance of hydrogen-oxidising bacteria. Taken together, these results expand our conceptual understanding of the mechanisms involved in ISA production, accumulation and biodegradation in a biogeochemically active cementitious GDF.
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Affiliation(s)
- Naji M Bassil
- Research Centre for Radwaste Disposal, Department of Earth and Environmental Sciences, The University of Manchester, Manchester M13 9PL, UK
- Williamson Research Centre for Molecular Environmental Science, Department of Earth and Environmental Sciences, The University of Manchester, Manchester M13 9PL, UK
| | - Joe S Small
- Research Centre for Radwaste Disposal, Department of Earth and Environmental Sciences, The University of Manchester, Manchester M13 9PL, UK
- National Nuclear Laboratory, Chadwick House, Birchwood Park, Warrington WA3 6AE, UK
| | - Jonathan R Lloyd
- Research Centre for Radwaste Disposal, Department of Earth and Environmental Sciences, The University of Manchester, Manchester M13 9PL, UK
- Williamson Research Centre for Molecular Environmental Science, Department of Earth and Environmental Sciences, The University of Manchester, Manchester M13 9PL, UK
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7
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Combrink M, du Preez I, Ronacher K, Walzl G, Loots DT. Time-Dependent Changes in Urinary Metabolome Before and After Intensive Phase Tuberculosis Therapy: A Pharmacometabolomics Study. ACTA ACUST UNITED AC 2019; 23:560-572. [DOI: 10.1089/omi.2019.0140] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Monique Combrink
- Human Metabolomics, North-West University, Potchefstroom, South Africa
| | - Ilse du Preez
- Human Metabolomics, North-West University, Potchefstroom, South Africa
| | - Katharina Ronacher
- Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, DST/NRF Centre of Excellence for Biomedical Tuberculosis Research/MRC Centre for Molecular and Cellular Biology, Stellenbosch University, Tygerberg, South Africa
- Mater Research Institute, The University of Queensland, Brisbane, Australia
| | - Gerhard Walzl
- Mater Research Institute, The University of Queensland, Brisbane, Australia
| | - Du Toit Loots
- Human Metabolomics, North-West University, Potchefstroom, South Africa
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8
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Biofilms: The Microbial "Protective Clothing" in Extreme Environments. Int J Mol Sci 2019; 20:ijms20143423. [PMID: 31336824 PMCID: PMC6679078 DOI: 10.3390/ijms20143423] [Citation(s) in RCA: 350] [Impact Index Per Article: 70.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 07/04/2019] [Accepted: 07/11/2019] [Indexed: 02/07/2023] Open
Abstract
Microbial biofilms are communities of aggregated microbial cells embedded in a self-produced matrix of extracellular polymeric substances (EPS). Biofilms are recalcitrant to extreme environments, and can protect microorganisms from ultraviolet (UV) radiation, extreme temperature, extreme pH, high salinity, high pressure, poor nutrients, antibiotics, etc., by acting as "protective clothing". In recent years, research works on biofilms have been mainly focused on biofilm-associated infections and strategies for combating microbial biofilms. In this review, we focus instead on the contemporary perspectives of biofilm formation in extreme environments, and describe the fundamental roles of biofilm in protecting microbial exposure to extreme environmental stresses and the regulatory factors involved in biofilm formation. Understanding the mechanisms of biofilm formation in extreme environments is essential for the employment of beneficial microorganisms and prevention of harmful microorganisms.
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9
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Kuippers G, Boothman C, Bagshaw H, Ward M, Beard R, Bryan N, Lloyd JR. The biogeochemical fate of nickel during microbial ISA degradation; implications for nuclear waste disposal. Sci Rep 2018; 8:8753. [PMID: 29884890 PMCID: PMC5993814 DOI: 10.1038/s41598-018-26963-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 05/04/2018] [Indexed: 12/14/2022] Open
Abstract
Intermediate level radioactive waste (ILW) generally contains a heterogeneous range of organic and inorganic materials, of which some are encapsulated in cement. Of particular concern are cellulosic waste items, which will chemically degrade under the conditions predicted during waste disposal, forming significant quantities of isosaccharinic acid (ISA), a strongly chelating ligand. ISA therefore has the potential to increase the mobility of a wide range of radionuclides via complex formation, including Ni-63 and Ni-59. Although ISA is known to be metabolized by anaerobic microorganisms, the biodegradation of metal-ISA complexes remains unexplored. This study investigates the fate of a Ni-ISA complex in Fe(III)-reducing enrichment cultures at neutral pH, representative of a microbial community in the subsurface. After initial sorption of Ni onto Fe(III)oxyhydroxides, microbial ISA biodegradation resulted in >90% removal of the remaining Ni from solution when present at 0.1 mM, whereas higher concentrations of Ni proved toxic. The microbial consortium associated with ISA degradation was dominated by close relatives to Clostridia and Geobacter species. Nickel was preferentially immobilized with trace amounts of biogenic amorphous iron sulfides. This study highlights the potential for microbial activity to help remove chelating agents and radionuclides from the groundwater in the subsurface geosphere surrounding a geodisposal facility.
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Affiliation(s)
- Gina Kuippers
- Research Centre for Radwaste Disposal & Williamson Research Centre for Molecular Environmental Science, School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | - Christopher Boothman
- Research Centre for Radwaste Disposal & Williamson Research Centre for Molecular Environmental Science, School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | - Heath Bagshaw
- Research Centre for Radwaste Disposal & Williamson Research Centre for Molecular Environmental Science, School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | - Michael Ward
- Leeds Electron Microscopy and Spectroscopy Centre, School of Chemical and Process Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Rebecca Beard
- Radioactive Waste Management Limited, Building 587, Curie Avenue, Harwell Oxford, Didcot, Oxfordshire, OX11 0RH, UK.,National Nuclear Laboratory Limited, Chadwick House, Warrington Road, Birchwood Park, Warrington, WA3 6AE, UK
| | - Nicholas Bryan
- National Nuclear Laboratory Limited, Chadwick House, Warrington Road, Birchwood Park, Warrington, WA3 6AE, UK
| | - Jonathan R Lloyd
- Research Centre for Radwaste Disposal & Williamson Research Centre for Molecular Environmental Science, School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
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10
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Bassil NM, Lloyd JR. Anaerobacillus isosaccharinicus sp. nov., an alkaliphilic bacterium which degrades isosaccharinic acid. Int J Syst Evol Microbiol 2018; 69:3666-3671. [PMID: 29580368 DOI: 10.1099/ijsem.0.002721] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Strain NB2006T was isolated from an isosaccharinate-degrading, nitrate-reducing enrichment culture in minimal freshwater medium at pH 10. Analysis of the 16S rRNA gene sequence indicated that this strain was most closely related to species of the newly established genus Anaerobacillus. This was supported by phenotypic and metabolic characterisation that showed that NB2006T was rod-shaped, Gram-stain-positive, motile and formed endospores. It was an aerotolerant anaerobe and an obligate alkaliphile that grew at pH 8.5-11, could tolerate up to 6 % (w/v) NaCl, and grew at a temperature between 10 and 40 °C. In addition, it could utilise a number of organic substrates, and was able to reduce nitrate and arsenate. The predominant cellular fatty acids were C16 : 0, C16 : 1ω11c, anteiso-C15 : 0, iso-C15 : 0, C16 : 1ω7c/iso-C15 : 0 2-OH and C14 : 0. The cell wall peptidoglycan contained meso-diaminopimelic acid and the DNA G+C content was 37.7 mol%. In silico DNA-DNA hybridization with the four known species of the genus Anaerobacillus showed 21.8, 21.9, 22.4, and 21.5 % relatedness to Anaerobacillusarseniciselenatis DSM 15340T, Anaerobacilus alkalidiazotrophicus DSM 22531T, Anaerobacillusalkalilacustris DSM 18345T, and Anaerobacillus macyae DSM 16346T, respectively. NB2006T differed from strains of other species of the genus Anaerobacillus in its ability to metabolise isosaccharinate, an alkaline hydrolysis product of cellulose. On the basis of the consensus of phylogenetic and phenotypic analyses, this strain represents a novel species of the genus Anaerobacillus, for which the name Anaerobacillus isosaccharinicus sp. nov. is proposed. The type strain is NB2006T (=DSM 100644T=LMG 30032T).
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Affiliation(s)
- Naji M Bassil
- Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, School of Earth and Environmental Sciences, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Jonathan R Lloyd
- Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, School of Earth and Environmental Sciences, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
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11
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The Impact of Alkaliphilic Biofilm Formation on the Release and Retention of Carbon Isotopes from Nuclear Reactor Graphite. Sci Rep 2018. [PMID: 29535412 PMCID: PMC5849744 DOI: 10.1038/s41598-018-22833-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
14C is an important consideration within safety assessments for proposed geological disposal facilities for radioactive wastes, since it is capable of re-entering the biosphere through the generation of 14C bearing gases. The irradiation of graphite moderators in the UK gas-cooled nuclear power stations has led to the generation of a significant volume of 14C-containing intermediate level wastes. Some of this 14C is present as a carbonaceous deposit on channel wall surfaces. Within this study, the potential of biofilm growth upon irradiated and 13C doped graphite at alkaline pH was investigated. Complex biofilms were established on both active and simulant samples. High throughput sequencing showed the biofilms to be dominated by Alcaligenes sp at pH 9.5 and Dietzia sp at pH 11.0. Surface characterisation revealed that the biofilms were limited to growth upon the graphite surface with no penetration of the deeper porosity. Biofilm formation resulted in the generation of a low porosity surface layer without the removal or modification of the surface deposits or the release of the associated 14C/13C. Our results indicated that biofilm formation upon irradiated graphite is likely to occur at the pH values studied, without any additional release of the associated 14C.
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12
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Floc Formation Reduces the pH Stress Experienced by Microorganisms Living in Alkaline Environments. Appl Environ Microbiol 2017; 83:AEM.02985-16. [PMID: 28087527 DOI: 10.1128/aem.02985-16] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 01/05/2017] [Indexed: 11/20/2022] Open
Abstract
The survival of microorganisms within a cementitious geological disposal facility for radioactive wastes heavily depends on their ability to survive the calcium-dominated, hyperalkaline conditions resulting from the dissolution of the cementitious materials. The results from this study show that the formation of flocs, composed of a complex mixture of extracellular polymeric substances (EPS), provides protection against alkaline pH values up to 13.0. The flocs were dominated by Alishewanella and Dietzia spp., producing a mannose-rich carbohydrate fraction incorporating extracellular DNA, resulting in Ca2+ sequestration. EPS provided a ∼10-μm thick layer around the cells within the center of the flocs, which were capable of growth at pH values of 11.0 and 11.5, maintaining internal pH values of 10.4 and 10.7, respectively. Microorganisms survived at a pH of 12.0, where an internal floc pH of 11.6 was observed, as was a reduced associated biomass. We observed limited floc survival (<2 weeks) at a pH of 13.0. This study demonstrates that flocs maintain lower internal pHs in response to the hyperalkaline conditions expected to occur within a cementitious geological disposal facility for radioactive wastes and indicates that floc communities within such a facility can survive at pHs up to 12.0.IMPORTANCE The role of extracellular polymeric substances (EPS) in the survival of microorganisms in hyperalkaline conditions is poorly understood. Here, we present the taxonomy, morphology, and chemical characteristics of an EPS-based microbial floc, formed by a consortium isolated from an anthropogenic hyperalkaline site. Short-term (<2 weeks) survival of the flocs at a pH of 13 was observed, with indefinite survival observed at a pH of 12.0. Measurements from micro-pH electrodes (10-μm-diameter tip) demonstrated that flocs maintain lower internal pHs in response to hyperalkaline conditions (pH 11.0, 11.5, and 12.0), demonstrating that floc formation and EPS production are survival strategies under hyperalkaline conditions. The results indicate how microbial communities may survive and propagate within the hyperalkaline environment that is expected to prevail in a cementitious geological disposal facility for radioactive wastes; the results are also relevant to the wider extremophile community.
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13
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Draft Whole-Genome Sequence of the Alkaliphilic Alishewanella aestuarii Strain HH-ZS, Isolated from Historical Lime Kiln Waste-Contaminated Soil. GENOME ANNOUNCEMENTS 2016; 4:4/6/e01447-16. [PMID: 28034857 PMCID: PMC5201056 DOI: 10.1128/genomea.01447-16] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Here, we present the whole-genome sequence of an environmental Gram-negative Alishewanella aestuarii strain (HH-ZS), isolated from the hyperalkaline contaminated soil of a historical lime kiln in Buxton, United Kingdom.
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14
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Kyeremeh IA, Charles CJ, Rout SP, Laws AP, Humphreys PN. Microbial Community Evolution Is Significantly Impacted by the Use of Calcium Isosaccharinic Acid as an Analogue for the Products of Alkaline Cellulose Degradation. PLoS One 2016; 11:e0165832. [PMID: 27806095 PMCID: PMC5091744 DOI: 10.1371/journal.pone.0165832] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Accepted: 10/18/2016] [Indexed: 12/03/2022] Open
Abstract
Diasteriomeric isosaccharinic acid (ISA) is an important consideration within safety assessments for the disposal of the United Kingdoms’ nuclear waste legacy, where it may potentially influence radionuclide migration. Since the intrusion of micro-organisms may occur within a disposal concept, the impact of ISA may be impacted by microbial metabolism. Within the present study we have established two polymicrobial consortia derived from a hyperalkaline soil. Here, α-ISA and a diatereomeric mix of ISAs’ were used as a sole carbon source, reflecting two common substrates appearing within the literature. The metabolism of ISA within these two consortia was similar, where ISA degradation resulted in the acetogenesis and hydrogenotrophic methanogenesis. The chemical data obtained confirm that the diastereomeric nature of ISA is likely to have no impact on its metabolism within alkaline environments. High throughput sequencing of the original soil showed a diverse community which, in the presence of ISA allowed for the dominance the Clostridiales associated taxa with Clostridium clariflavum prevalent. Further taxonomic investigation at the genus level showed that there was in fact a significant difference (p = 0.004) between the two community profiles. Our study demonstrates that the selection of carbon substrate is likely to have a significant impact on microbial community composition estimations, which may have implications with respect to a safety assessment of an ILW-GDF.
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Affiliation(s)
- Isaac A. Kyeremeh
- Department of Biology, School of Applied Sciences, University of Huddersfield, Huddersfield, West Yorkshire, United Kingdom
| | - Christopher J. Charles
- Department of Biology, School of Applied Sciences, University of Huddersfield, Huddersfield, West Yorkshire, United Kingdom
| | - Simon P. Rout
- Department of Biology, School of Applied Sciences, University of Huddersfield, Huddersfield, West Yorkshire, United Kingdom
| | - Andrew P. Laws
- Department of Biology, School of Applied Sciences, University of Huddersfield, Huddersfield, West Yorkshire, United Kingdom
| | - Paul N. Humphreys
- Department of Biology, School of Applied Sciences, University of Huddersfield, Huddersfield, West Yorkshire, United Kingdom
- * E-mail:
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