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Zhang L, Kang-Yun CS, Lu X, Chang J, Liang X, Pierce EM, Semrau JD, Gu B. Adsorption and intracellular uptake of mercuric mercury and methylmercury by methanotrophs and methylating bacteria. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2023; 331:121790. [PMID: 37187279 DOI: 10.1016/j.envpol.2023.121790] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 04/25/2023] [Accepted: 05/07/2023] [Indexed: 05/17/2023]
Abstract
The cell surface adsorption and intracellular uptake of mercuric Hg(II) and methylmercury (MeHg) are important in determining the fate and transformation of Hg in the environment. However, current information is limited about their interactions with two important groups of microorganisms, i.e., methanotrophs and Hg(II)-methylating bacteria, in aquatic systems. This study investigated the adsorption and uptake dynamics of Hg(II) and MeHg by three strains of methanotrophs, Methylomonas sp. Strain EFPC3, Methylosinus trichosporium OB3b, and Methylococcus capsulatus Bath, and two Hg(II)-methylating bacteria, Pseudodesulfovibrio mercurii ND132 and Geobacter sulfurreducens PCA. Distinctive behaviors of these microorganisms towards Hg(II) and MeHg adsorption and intracellular uptake were observed. The methanotrophs generally took up 60-80% of inorganic Hg(II) inside cells after 24 h incubation, lower than methylating bacteria (>90%). Approximately 80-95% of MeHg was rapidly taken up by all the tested methanotrophs within 24 h. In contrast, after the same time, G. sulfurreducens PCA adsorbed 70% but took up <20% of MeHg, while P. mercurii ND132 only adsorbed 20% but took up negligible amounts of MeHg. These results suggest that microbial surface adsorption and intracellular uptake of Hg(II) and MeHg depend on the specific types of microbes and appear to be related to microbial physiology that requires further detailed investigation. Despite being incapable of methylating Hg(II), methanotrophs play important roles in immobilizing both Hg(II) and MeHg, potentially influencing their bioavailability and trophic transfer. Therefore, methanotrophs are not only important sinks for methane but also for Hg(II) and MeHg and can influence the global cycling of C and Hg.
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Affiliation(s)
- Lijie Zhang
- Department of Chemistry and Environmental Science, New Jersey Institute of Technology, Newark, NJ 07102, USA; Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
| | - Christina S Kang-Yun
- Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, MI 48109, USA
| | - Xia Lu
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Jin Chang
- Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, MI 48109, USA
| | - Xujun Liang
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Eric M Pierce
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Jeremy D Semrau
- Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, MI 48109, USA
| | - Baohua Gu
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA; Department of Biosystems Engineering and Soil Science, University of Tennesee, Knoxville, TN 37996, USA
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Altshuler I, Raymond-Bouchard I, Magnuson E, Tremblay J, Greer CW, Whyte LG. Unique high Arctic methane metabolizing community revealed through in situ 13CH 4-DNA-SIP enrichment in concert with genome binning. Sci Rep 2022; 12:1160. [PMID: 35064149 PMCID: PMC8782848 DOI: 10.1038/s41598-021-04486-z] [Citation(s) in RCA: 4] [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: 07/19/2021] [Accepted: 11/30/2021] [Indexed: 12/15/2022] Open
Abstract
Greenhouse gas (GHG) emissions from Arctic permafrost soils create a positive feedback loop of climate warming and further GHG emissions. Active methane uptake in these soils can reduce the impact of GHG on future Arctic warming potential. Aerobic methane oxidizers are thought to be responsible for this apparent methane sink, though Arctic representatives of these organisms have resisted culturing efforts. Here, we first used in situ gas flux measurements and qPCR to identify relative methane sink hotspots at a high Arctic cytosol site, we then labeled the active microbiome in situ using DNA Stable Isotope Probing (SIP) with heavy 13CH4 (at 100 ppm and 1000 ppm). This was followed by amplicon and metagenome sequencing to identify active organisms involved in CH4 metabolism in these high Arctic cryosols. Sequencing of 13C-labeled pmoA genes demonstrated that type II methanotrophs (Methylocapsa) were overall the dominant active methane oxidizers in these mineral cryosols, while type I methanotrophs (Methylomarinovum) were only detected in the 100 ppm SIP treatment. From the SIP-13C-labeled DNA, we retrieved nine high to intermediate quality metagenome-assembled genomes (MAGs) belonging to the Proteobacteria, Gemmatimonadetes, and Chloroflexi, with three of these MAGs containing genes associated with methanotrophy. A novel Chloroflexi MAG contained a mmoX gene along with other methane oxidation pathway genes, identifying it as a potential uncultured methane oxidizer. This MAG also contained genes for copper import, synthesis of biopolymers, mercury detoxification, and ammonia uptake, indicating that this bacterium is strongly adapted to conditions in active layer permafrost and providing new insights into methane biogeochemical cycling. In addition, Betaproteobacterial MAGs were also identified as potential cross-feeders with methanotrophs in these Arctic cryosols. Overall, in situ SIP labeling combined with metagenomics and genome binning demonstrated to be a useful tool for discovering and characterizing novel organisms related to specific microbial functions or biogeochemical cycles of interest. Our findings reveal a unique and active Arctic cryosol microbial community potentially involved in CH4 cycling.
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Affiliation(s)
- Ianina Altshuler
- Department of Natural Resource Sciences, McGill University, 21,111 Lakeshore Rd., Ste. Anne de Bellevue, QC, H9X 3V9, Canada.
- Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences NMBU, Universitetstunet 3, 1430, Ås, Norway.
| | - Isabelle Raymond-Bouchard
- Department of Natural Resource Sciences, McGill University, 21,111 Lakeshore Rd., Ste. Anne de Bellevue, QC, H9X 3V9, Canada
| | - Elisse Magnuson
- Department of Natural Resource Sciences, McGill University, 21,111 Lakeshore Rd., Ste. Anne de Bellevue, QC, H9X 3V9, Canada
| | - Julien Tremblay
- Energy, Mining and Environment Research Centre, National Research Council of Canada, 6100 Royalmount Ave., Montreal, QC, H4P 2R2, Canada
| | - Charles W Greer
- Department of Natural Resource Sciences, McGill University, 21,111 Lakeshore Rd., Ste. Anne de Bellevue, QC, H9X 3V9, Canada
- Energy, Mining and Environment Research Centre, National Research Council of Canada, 6100 Royalmount Ave., Montreal, QC, H4P 2R2, Canada
| | - Lyle G Whyte
- Department of Natural Resource Sciences, McGill University, 21,111 Lakeshore Rd., Ste. Anne de Bellevue, QC, H9X 3V9, Canada
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Yun J, Crombie AT, Ul Haque MF, Cai Y, Zheng X, Wang J, Jia Z, Murrell JC, Wang Y, Du W. Revealing the community and metabolic potential of active methanotrophs by targeted metagenomics in the Zoige wetland of the Tibetan Plateau. Environ Microbiol 2021; 23:6520-6535. [PMID: 34390603 DOI: 10.1111/1462-2920.15697] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 07/27/2021] [Accepted: 07/27/2021] [Indexed: 01/21/2023]
Abstract
The Zoige wetland of the Tibetan Plateau is one of the largest alpine wetlands in the world and a major emission source of methane. Methane oxidation by methanotrophs can counteract the global warming effect of methane released in the wetlands. Understanding methanotroph activity, diversity and metabolism at the molecular level can guide the isolation of the uncultured microorganisms and inform strategy-making decisions and policies to counteract global warming in this unique ecosystem. Here we applied DNA stable isotope probing using 13 C-labelled methane to label the genomes of active methanotrophs, examine the methane oxidation potential and recover metagenome-assembled genomes (MAGs) of active methanotrophs. We found that gammaproteobacteria of type I methanotrophs are responsible for methane oxidation in the wetland. We recovered two phylogenetically novel methanotroph MAGs distantly related to extant Methylobacter and Methylovulum. They belong to type I methanotrophs of gammaproteobacteria, contain both mxaF and xoxF types of methanol dehydrogenase coding genes, and participate in methane oxidation via H4 MPT and RuMP pathways. Overall, the community structure of active methanotrophs and their methanotrophic pathways revealed by DNA-SIP metagenomics and retrieved methanotroph MAGs highlight the importance of methanotrophs in suppressing methane emission in the wetland under the scenario of global warming.
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Affiliation(s)
- Juanli Yun
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Andrew T Crombie
- School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | | | - Yuanfeng Cai
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, Jiangsu Province, 210008, China
| | - Xiaowei Zheng
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Jian Wang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Zhongjun Jia
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, Jiangsu Province, 210008, China
| | - J Colin Murrell
- School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Yanfen Wang
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, 10049, China.,CAS Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing, 100101, China
| | - Wenbin Du
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.,Savaid Medical School, University of the Chinese Academy of Sciences, Beijing, 10049, China
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Karthikeyan OP, Smith TJ, Dandare SU, Parwin KS, Singh H, Loh HX, Cunningham MR, Williams PN, Nichol T, Subramanian A, Ramasamy K, Kumaresan D. Metal(loid) speciation and transformation by aerobic methanotrophs. MICROBIOME 2021; 9:156. [PMID: 34229757 PMCID: PMC8262016 DOI: 10.1186/s40168-021-01112-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 06/09/2021] [Indexed: 05/06/2023]
Abstract
Manufacturing and resource industries are the key drivers for economic growth with a huge environmental cost (e.g. discharge of industrial effluents and post-mining substrates). Pollutants from waste streams, either organic or inorganic (e.g. heavy metals), are prone to interact with their physical environment that not only affects the ecosystem health but also the livelihood of local communities. Unlike organic pollutants, heavy metals or trace metals (e.g. chromium, mercury) are non-biodegradable, bioaccumulate through food-web interactions and are likely to have a long-term impact on ecosystem health. Microorganisms provide varied ecosystem services including climate regulation, purification of groundwater, rehabilitation of contaminated sites by detoxifying pollutants. Recent studies have highlighted the potential of methanotrophs, a group of bacteria that can use methane as a sole carbon and energy source, to transform toxic metal (loids) such as chromium, mercury and selenium. In this review, we synthesise recent advances in the role of essential metals (e.g. copper) for methanotroph activity, uptake mechanisms alongside their potential to transform toxic heavy metal (loids). Case studies are presented on chromium, selenium and mercury pollution from the tanneries, coal burning and artisanal gold mining, respectively, which are particular problems in the developing economy that we propose may be suitable for remediation by methanotrophs. Video Abstract.
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Affiliation(s)
- Obulisamy Parthiba Karthikeyan
- School of Biological Sciences & Institute for Global Food Security, Queen’s University Belfast, 19 Chlorine Gardens, Belfast, UK
- Civil and Environmental Engineering, University of Michigan, Ann Arbor, MI USA
- Department of Engineering Technology, College of Technology, University of Houston, Houston, TX USA
| | - Thomas J. Smith
- Biomolecular Sciences Research Centre, Sheffield Hallam University, Sheffield, UK
| | - Shamsudeen Umar Dandare
- School of Biological Sciences & Institute for Global Food Security, Queen’s University Belfast, 19 Chlorine Gardens, Belfast, UK
| | - Kamaludeen Sara Parwin
- Department of Environmental Sciences, Tamil Nadu Agricultural University, Coimbatore, India
| | - Heetasmin Singh
- Department of Chemistry, University of Guyana, Georgetown, Guyana
| | - Hui Xin Loh
- School of Biological Sciences & Institute for Global Food Security, Queen’s University Belfast, 19 Chlorine Gardens, Belfast, UK
| | - Mark R Cunningham
- School of Biological Sciences & Institute for Global Food Security, Queen’s University Belfast, 19 Chlorine Gardens, Belfast, UK
| | - Paul Nicholas Williams
- School of Biological Sciences & Institute for Global Food Security, Queen’s University Belfast, 19 Chlorine Gardens, Belfast, UK
| | - Tim Nichol
- Biomolecular Sciences Research Centre, Sheffield Hallam University, Sheffield, UK
| | | | | | - Deepak Kumaresan
- School of Biological Sciences & Institute for Global Food Security, Queen’s University Belfast, 19 Chlorine Gardens, Belfast, UK
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Detoxification, Active Uptake, and Intracellular Accumulation of Chromium Species by a Methane-Oxidizing Bacterium. Appl Environ Microbiol 2021; 87:AEM.00947-20. [PMID: 33127813 PMCID: PMC7783347 DOI: 10.1128/aem.00947-20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Accepted: 10/20/2020] [Indexed: 01/28/2023] Open
Abstract
M. capsulatus Bath is a well-characterized aerobic methane-oxidizing bacterium that has become a model system for biotechnological development of methanotrophs to perform useful reactions for environmental cleanup and for making valuable chemicals and biological products using methane gas. Interest in such technology has increased recently owing to increasing availability of low-cost methane from fossil and biological sources. Here, it is demonstrated that this versatile methanotroph can reduce the toxic contaminating heavy metal chromium(VI) to the less toxic form chromium(III) while accumulating the chromium(III) within the cells. This is expected to diminish the bioavailability of the chromium and make it less likely to be reoxidized to chromium(VI). Thus, M. capsulatus has the capacity to perform methane-driven remediation of chromium-contaminated water and other materials and to accumulate the chromium in the low-toxicity chromium(III) form within the cells. Despite the wide-ranging proscription of hexavalent chromium, chromium(VI) remains among the major polluting heavy metals worldwide. Aerobic methane-oxidizing bacteria are widespread environmental microorganisms that can perform diverse reactions using methane as the feedstock. The methanotroph Methylococcus capsulatus Bath, like many other microorganisms, detoxifies chromium(VI) by reduction to chromium(III). Here, the interaction of chromium species with M. capsulatus Bath was examined in detail by using a range of techniques. Cell fractionation and high-performance liquid chromatography–inductively coupled plasma mass spectrometry (HPLC–ICP-MS) indicated that externally provided chromium(VI) underwent reduction and was then taken up into the cytoplasmic and membranous fractions of the cells. This was confirmed by X-ray photoelectron spectroscopy (XPS) of intact cultures that indicated negligible chromium on the surfaces of or outside the cells. Distribution of chromium and other elements within intact and sectioned cells, as observed via transmission electron microscopy (TEM) combined with energy-dispersive X-ray spectroscopy (EDX) and electron energy loss spectroscopy (EELS), was consistent with the cytoplasm/membrane location of the chromium(III), possibly as chromium phosphate. The cells could also take up chromium(III) directly from the medium in a metabolism-dependent fashion and accumulate it. These results indicate a novel pattern of interaction with chromium species distinct from that observed previously with other microorganisms. They also suggest that M. capsulatus and similar methanotrophs may contribute directly to chromium(VI) reduction and accumulation in mixed communities of microorganisms that are able to perform methane-driven remediation of chromium(VI). IMPORTANCEM. capsulatus Bath is a well-characterized aerobic methane-oxidizing bacterium that has become a model system for biotechnological development of methanotrophs to perform useful reactions for environmental cleanup and for making valuable chemicals and biological products using methane gas. Interest in such technology has increased recently owing to increasing availability of low-cost methane from fossil and biological sources. Here, it is demonstrated that this versatile methanotroph can reduce the toxic contaminating heavy metal chromium(VI) to the less toxic form chromium(III) while accumulating the chromium(III) within the cells. This is expected to diminish the bioavailability of the chromium and make it less likely to be reoxidized to chromium(VI). Thus, M. capsulatus has the capacity to perform methane-driven remediation of chromium-contaminated water and other materials and to accumulate the chromium in the low-toxicity chromium(III) form within the cells.
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Jung GY, Rhee SK, Han YS, Kim SJ. Genomic and Physiological Properties of a Facultative Methane-Oxidizing Bacterial Strain of Methylocystis sp. from a Wetland. Microorganisms 2020; 8:microorganisms8111719. [PMID: 33147874 PMCID: PMC7716213 DOI: 10.3390/microorganisms8111719] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 10/23/2020] [Accepted: 10/30/2020] [Indexed: 01/07/2023] Open
Abstract
Methane-oxidizing bacteria are crucial players in controlling methane emissions. This study aimed to isolate and characterize a novel wetland methanotroph to reveal its role in the wetland environment based on genomic information. Based on phylogenomic analysis, the isolated strain, designated as B8, is a novel species in the genus Methylocystis. Strain B8 grew in a temperature range of 15 °C to 37 °C (optimum 30–35 °C) and a pH range of 6.5 to 10 (optimum 8.5–9). Methane, methanol, and acetate were used as carbon sources. Hydrogen was produced under oxygen-limited conditions. The assembled genome comprised of 3.39 Mbp and 59.9 mol% G + C content. The genome contained two types of particulate methane monooxygenases (pMMO) for low-affinity methane oxidation (pMMO1) and high-affinity methane oxidation (pMMO2). It was revealed that strain B8 might survive atmospheric methane concentration. Furthermore, the genome had various genes for hydrogenase, nitrogen fixation, polyhydroxybutyrate synthesis, and heavy metal resistance. This metabolic versatility of strain B8 might enable its survival in wetland environments.
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Affiliation(s)
- Gi-Yong Jung
- Geologic Environment Research Division, Korea Institute of Geoscience and Mineral Resources, Daejeon 34132, Korea;
- Department of Microbiology, Chungbuk National University, Cheongju 28644, Korea;
| | - Sung-Keun Rhee
- Department of Microbiology, Chungbuk National University, Cheongju 28644, Korea;
| | - Young-Soo Han
- Department of Environmental Engineering, Chungnam National University, Daejeon 34134, Korea;
| | - So-Jeong Kim
- Geologic Environment Research Division, Korea Institute of Geoscience and Mineral Resources, Daejeon 34132, Korea;
- Correspondence: ; Tel.: +82-42-868-3311; Fax: +82-42-868-3414
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7
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Insights into growth kinetics and roles of enzymes of Krebs' cycle and sulfur oxidation during exochemolithoheterotrophic growth of Achromobacter aegrifaciens NCCB 38021 on succinate with thiosulfate as the auxiliary electron donor. Arch Microbiol 2020; 203:561-578. [PMID: 32989476 DOI: 10.1007/s00203-020-02028-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 08/18/2020] [Accepted: 09/02/2020] [Indexed: 10/23/2022]
Abstract
Achromobacter aegrifaciens NCCB 38021 was grown heterotrophically on succinate versus exochemolithoheterotrophically on succinate with thiosulfate as auxiliary electron donor. In batch culture, no significant differences in specific molar growth yield or specific growth rate were found for the two growth conditions, but in continuous culture in the succinate-limited chemostat, the maximum specific growth yield coefficient increased by 23.3% with thiosulfate present, consistent with previous studies of endo- and exochemolithoheterotrophs and thermodynamic predictions. Thiosulfate oxidation was coupled to respiration at cytochrome c551, and thiosulfate-dependent ATP biosynthesis occurred. Specific activities of cytochrome c-linked thiosulfate dehydrogenase (E.C. 1.8.2.2) and two other enzymes of sulfur metabolism were significantly higher in exochemolithoheterotrophically grown cell extracts, while those of succinyl-transferring 2-oxoglutarate dehydrogenase (E.C. 1.2.4.2), fumarate hydratase (E.C. 4.2.1.2) and malate dehydrogenase (NAD+, E.C. 1.1.1.37) were significantly lower-presumably owing to less need to generate reducing equivalents during Krebs' cycle, since they could be produced from thiosulfate oxidation.
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8
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Challa S, Smith TJ. Isolation of a methane-oxidizing bacterium that bioremediates hexavalent chromium from a formerly industrialized Suburban River. Lett Appl Microbiol 2020; 71:287-293. [PMID: 32470995 DOI: 10.1111/lam.13330] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 05/15/2020] [Accepted: 05/18/2020] [Indexed: 01/21/2023]
Abstract
Sediment samples were taken from sediment adjacent to a suburban river in Sheffield in Northern England that had suffered heavy metal pollution due to previous activity of the steel industry (between the 17th and 19th centuries). The most abundant heavy metals found in the samples were lead, chromium, nickel, arsenic and cobalt, with maximum concentrations of 412·80, 25·232, 25·196, 8·123 and 7·66 mg kg-1 , respectively. Enrichment cultures were set up using methane as carbon and energy source, as a result of which a strain of methanotroph was isolated that was shown via 16S rRNA gene sequencing to be a strain Methylomonas koyamae and given the designation SHU1. M. koyamae SHU1 removed hexavalent chromium from an initial concentration of 10 ppm, which was inhibited by the metabolic inhibitor sodium azide or the methane monooxygenase inhibitor phenylacetylene. To the authors' knowledge, this is the first description of a strain of the widely environmentally distributed genus Methylomonas that is capable of remediating hexavalent chromium. SIGNIFICANCE AND IMPACT OF THE STUDY: Aerobic methanotrophic bacteria are known for bioremediation of an increasing range of organic and inorganic pollutants, using methane as carbon and energy source. Previously, one laboratory methanotroph strain, Methylococcus capsulatus Bath, was known to bioremediate toxic chromium (VI) by reducing it to chromium (III). Here, a newly isolated methanotroph strain, Methylomonas koyamae SHU1, has been shown able to remediate chromium (VI). This indicates that chromium (VI) bioremediation is not unique to M. capsulatus and moreover adds weight to the suggestion that methanotrophs may contribute directly to chromium (VI) detoxification in nature and in polymicrobial bioremediation fed with methane.
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Affiliation(s)
- S Challa
- Biomolecular Sciences Research Centre, College of Heath, Wellbeing and Life Sciences, Sheffield Hallam University, Sheffield, UK
| | - T J Smith
- Biomolecular Sciences Research Centre, College of Heath, Wellbeing and Life Sciences, Sheffield Hallam University, Sheffield, UK
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9
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Norambuena J, Miller M, Boyd JM, Barkay T. Expression and regulation of the mer operon in Thermus thermophilus. Environ Microbiol 2020; 22:1619-1634. [PMID: 32090420 DOI: 10.1111/1462-2920.14953] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 01/16/2020] [Indexed: 11/25/2022]
Abstract
Mercury (Hg) is a highly toxic and widely distributed heavy metal, which some Bacteria and Archaea detoxify by the reduction of ionic Hg (Hg[II]) to the elemental volatile form, Hg(0). This activity is specified by the mer operon. The mer operon of the deeply branching thermophile Thermus thermophilus HB27 encodes for, an O-acetyl-l-homoacetylserine sulfhydrylase (Oah2), a transcriptional regulator (MerR), a hypothetical protein (hp) and a mercuric reductase (MerA). Here, we show that this operon has two convergently expressed and differentially regulated promoters. An upstream promoter, P oah , controls the constitutive transcription of the entire operon and a second promoter (P mer ), located within merR, is responsive to Hg(II). In the absence of Hg(II), the transcription of merA is basal and when Hg(II) is present, merA transcription is induced. This response to Hg(II) is controlled by MerR and genetic evidence suggests that MerR acts as a repressor and activator of P mer . When the whole merR, including P mer , is removed, merA is transcribed from P oah independently of Hg(II). These results suggest that the transcriptional regulation of mer in T. thermophilus is both similar to, and different from, the well-documented regulation of proteobacterial mer systems, possibly representing an early step in the evolution of mer-operon regulation.
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Affiliation(s)
- Javiera Norambuena
- Department of Biochemistry and Microbiology, Rutgers, The State University of New Jersey, New Brunswick, 08901, New Jersey, USA
| | - Maximilian Miller
- Department of Biochemistry and Microbiology, Rutgers, The State University of New Jersey, New Brunswick, 08901, New Jersey, USA
| | - Jeffrey M Boyd
- Department of Biochemistry and Microbiology, Rutgers, The State University of New Jersey, New Brunswick, 08901, New Jersey, USA
| | - Tamar Barkay
- Department of Biochemistry and Microbiology, Rutgers, The State University of New Jersey, New Brunswick, 08901, New Jersey, USA
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Methane oxidation coupled to vanadate reduction in a membrane biofilm batch reactor under hypoxic condition. Biodegradation 2019; 30:457-466. [PMID: 31410606 DOI: 10.1007/s10532-019-09887-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Accepted: 07/25/2019] [Indexed: 10/26/2022]
Abstract
This study shows vanadate (V(V)) reduction in a methane (CH4) based membrane biofilm batch reactor when the concentration of dissolved oxygen (O2) was extremely low. V(IV) was the dominant products formed from V(V) bio-reduction, and majority of produced V(IV) transformed into precipitates with green color. Quantitative polymerase chain reaction and Illumina sequencing analysis showed that archaea methanosarcina were significantly enriched. Metagenomic predictive analysis further showed the enrichment of genes associated with reverse methanogenesis pathway, the key CH4-activating mechanism for anaerobic methane oxidation (AnMO), as well as the enrichment of genes related to acetate synthesis, in archaea. The enrichment of aerobic methanotrophs Methylococcus and Methylomonas implied their role in CH4 activation using trace level of O2, or their participation in V(V) reduction.
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11
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Shi LD, Chen YS, Du JJ, Hu YQ, Shapleigh JP, Zhao HP. Metagenomic Evidence for a Methylocystis Species Capable of Bioremediation of Diverse Heavy Metals. Front Microbiol 2019; 9:3297. [PMID: 30687279 PMCID: PMC6333641 DOI: 10.3389/fmicb.2018.03297] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Accepted: 12/18/2018] [Indexed: 02/01/2023] Open
Abstract
Heavy metal pollution has become an increasingly serious problem worldwide. Co-contamination with toxic mercury (Hg) and arsenic (As) presents a particularly difficult bioremediation trouble. By oxidizing the greenhouse gas methane, methanotrophs have been demonstrated to have high denitrification activity in eutrophic waters, indicating their possible potential for use in bioremediation of Hg(II) and As(V) in polluted water. Using metagenomics, a novel Methylocystis species (HL18), which was one of the most prevalent bacteria (9.9% of the relative abundance) in a CH4-based bio-reactor, is described here. The metagenomic-assembled genome (MAG) HL18 had gene products whose average amino acid identity against other known Methylocystis species varied from 69 to 85%, higher than the genus threshold but lower than the species boundary. Genomic analysis indicated that HL18 possessed all the genes necessary for the reduction of Hg(II) and As(V). Phylogenetic investigation of mercuric reductase (MerA) found that the HL18 protein was most closely affiliated with proteins from two Hg(II)-reducing bacteria, Bradyrhizobium sp. strain CCH5-F6 and Paracoccus halophilus. The genomic organization and phylogeny of the genes in the As(V)-reducing operon (arsRCCB) had significant identity with those from a As(V)-reducing bacterium belonging to the Rhodopseudomonas genus, indicating their reduction capability of As(V). Further analysis found that at least eight genera of methanotrophs possess both Hg(II) and As(V) reductases, illustrating the generally overlooked metabolic potential of methanotrophs. These results suggest that methanotrophs have greater bioremediation potential in heavy metal contaminated water than has been appreciated and could play an important role in the mitigation of heavy metal toxicity of contaminated wastewater.
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Affiliation(s)
- Ling-Dong Shi
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.,Zhejiang Province Key Laboratory for Water Pollution Control and Environment, Zhejiang University, Hangzhou, China.,MOE Key Lab of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
| | - Yu-Shi Chen
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
| | - Jia-Jie Du
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
| | - Yi-Qing Hu
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
| | - James P Shapleigh
- Department of Microbiology, Cornell University, Ithaca, NY, United States
| | - He-Ping Zhao
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.,Zhejiang Province Key Laboratory for Water Pollution Control and Environment, Zhejiang University, Hangzhou, China.,MOE Key Lab of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
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12
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Vassallo J, Besinis A, Boden R, Handy RD. The minimum inhibitory concentration (MIC) assay with Escherichia coli: An early tier in the environmental hazard assessment of nanomaterials? ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2018; 162:633-646. [PMID: 30033160 DOI: 10.1016/j.ecoenv.2018.06.085] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Revised: 06/25/2018] [Accepted: 06/27/2018] [Indexed: 06/08/2023]
Abstract
There are now over a thousand nano-containing products on the market and the antibacterial properties of some nanomaterials has created interest in their use as cleaning agents, biocides and disinfectants. Engineered nanomaterials (ENMs) are being released into the environment and this raises concerns about their effects on microbes in the receiving ecosystems. This study evaluated the bacterial toxicity of a wide range of nanomaterials with different surface coatings on Escherichia coli K-12 MG1655. The minimum inhibitory concentration (MIC) assay, which quantifies the threshold for growth inhibition in suspensions of bacteria, was used to rank the toxicity of silver (Ag), cupric oxide (CuO), cadmium telluride (CdTe) quantum dots, titanium dioxide (TiO2), nanodiamonds and multi-walled carbon nanotubes (MWCNTs). Bacteria were exposed for 12 h at 37 °C to a dilution series of the test suspensions in 96-well plates. The precision and accuracy of the method was good with coefficients of variation < 10%. In terms of the measured MIC values, the toxicity order of the ENMs was as follows: CdTe quantum dots ammonium-coated, 6 mg L-1 > Ag nanoparticles, 12 mg L-1 > CdTe quantum dots carboxylate-coated, 25 mg L-1 > CdTe quantum dots polyethylene glycol-coated, 100 mg L-1. The MIC values were above the highest test concentration used (100 mg L-1) for CuO, TiO2, nanodiamonds and MWCNTs, indicating low toxicity. The MIC assay can be a useful tool for the initial steps of ENMs hazard assessment.
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Affiliation(s)
- J Vassallo
- School of Biological and Marine Sciences, Faculty of Science and Engineering, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK; Sustainable Earth Institute, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK
| | - A Besinis
- School of Biological and Marine Sciences, Faculty of Science and Engineering, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK; School of Engineering, Faculty of Science and Engineering, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK; Plymouth University Peninsula Schools of Medicine and Dentistry, University of Plymouth, John Bull Building, Tamar Science Park, Plymouth PL6 8BU, UK
| | - R Boden
- School of Biological and Marine Sciences, Faculty of Science and Engineering, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK; Sustainable Earth Institute, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK
| | - R D Handy
- School of Biological and Marine Sciences, Faculty of Science and Engineering, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK; Sustainable Earth Institute, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK.
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13
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Abstract
Copper-binding metallophores, or chalkophores, play a role in microbial copper homeostasis that is analogous to that of siderophores in iron homeostasis. The best-studied chalkophores are members of the methanobactin (Mbn) family-ribosomally produced, posttranslationally modified natural products first identified as copper chelators responsible for copper uptake in methane-oxidizing bacteria. To date, Mbns have been characterized exclusively in those species, but there is genomic evidence for their production in a much wider range of bacteria. This review addresses the current state of knowledge regarding the function, biosynthesis, transport, and regulation of Mbns. While the roles of several proteins in these processes are supported by substantial genetic and biochemical evidence, key aspects of Mbn manufacture, handling, and regulation remain unclear. In addition, other natural products that have been proposed to mediate copper uptake as well as metallophores that have biologically relevant roles involving copper binding, but not copper uptake, are discussed.
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Affiliation(s)
- Grace E Kenney
- Department of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, USA; ,
| | - Amy C Rosenzweig
- Department of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, USA; ,
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA
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14
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Eswayah AS, Smith TJ, Scheinost AC, Hondow N, Gardiner PHE. Microbial transformations of selenite by methane-oxidizing bacteria. Appl Microbiol Biotechnol 2017. [PMID: 28646447 PMCID: PMC5554269 DOI: 10.1007/s00253-017-8380-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Methane-oxidizing bacteria are well known for their role in the global methane cycle and their potential for microbial transformation of wide range of hydrocarbon and chlorinated hydrocarbon pollution. Recently, it has also emerged that methane-oxidizing bacteria interact with inorganic pollutants in the environment. Here, we report what we believe to be the first study of the interaction of pure strains of methane-oxidizing bacteria with selenite. Results indicate that the commonly used laboratory model strains of methane-oxidizing bacteria, Methylococcus capsulatus (Bath) and Methylosinus trichosporium OB3b, are both able to reduce the toxic selenite (SeO32−) but not selenate (SeO42−) to red spherical nanoparticulate elemental selenium (Se0), which was characterized via energy-dispersive X-ray spectroscopy (EDXS), X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). The cultures also produced volatile selenium-containing species, which suggests that both strains may have an additional activity that can transform either Se0 or selenite into volatile methylated forms of selenium. Transmission electron microscopy (TEM) measurements and experiments with the cell fractions cytoplasm, cell wall and cell membrane show that the nanoparticles are formed mainly on the cell wall. Collectively, these results are promising for the use of methane-oxidizing bacteria for bioremediation or suggest possible uses in the production of selenium nanoparticles for biotechnology.
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Affiliation(s)
- Abdurrahman S Eswayah
- Biomolecular Sciences Research Centre, Sheffield Hallam University, Sheffield, UK
- Biotechnology Research Centre, Tripoli, Libya
| | - Thomas J Smith
- Biomolecular Sciences Research Centre, Sheffield Hallam University, Sheffield, UK
| | - Andreas C Scheinost
- The Rossendorf Beamline at ESRF, F-38043, Grenoble, France
- Institute of Resource Ecology, Helmholtz Zentrum Dresden Rossendorf, D-01328, Dresden, Germany
| | - Nicole Hondow
- School of Chemical and Process Engineering, University of Leeds, Leeds, UK
| | - Philip H E Gardiner
- Biomolecular Sciences Research Centre, Sheffield Hallam University, Sheffield, UK.
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15
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Lu X, Liu Y, Johs A, Zhao L, Wang T, Yang Z, Lin H, Elias DA, Pierce EM, Liang L, Barkay T, Gu B. Anaerobic Mercury Methylation and Demethylation by Geobacter bemidjiensis Bem. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:4366-73. [PMID: 27019098 DOI: 10.1021/acs.est.6b00401] [Citation(s) in RCA: 88] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Microbial methylation and demethylation are two competing processes controlling the net production and bioaccumulation of neurotoxic methylmercury (MeHg) in natural ecosystems. Although mercury (Hg) methylation by anaerobic microorganisms and demethylation by aerobic Hg-resistant bacteria have both been extensively studied, little attention has been given to MeHg degradation by anaerobic bacteria, particularly the iron-reducing bacterium Geobacter bemidjiensis Bem. Here we report, for the first time, that the strain G. bemidjiensis Bem can mediate a suite of Hg transformations, including Hg(II) reduction, Hg(0) oxidation, MeHg production and degradation under anoxic conditions. Results suggest that G. bemidjiensis utilizes a reductive demethylation pathway to degrade MeHg, with elemental Hg(0) as the major reaction product, possibly due to the presence of genes encoding homologues of an organomercurial lyase (MerB) and a mercuric reductase (MerA). In addition, the cells can strongly sorb Hg(II) and MeHg, reduce or oxidize Hg, resulting in both time and concentration-dependent Hg species transformations. Moderate concentrations (10-500 μM) of Hg-binding ligands such as cysteine enhance Hg(II) methylation but inhibit MeHg degradation. These findings indicate a cycle of Hg methylation and demethylation among anaerobic bacteria, thereby influencing net MeHg production in anoxic water and sediments.
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Affiliation(s)
- Xia Lu
- School of Nuclear Science and Technology, Lanzhou University , Lanzhou, China
- Environmental Sciences Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
| | - Yurong Liu
- Environmental Sciences Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , Beijing, China
| | - Alexander Johs
- Environmental Sciences Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
| | - Linduo Zhao
- Environmental Sciences Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
| | - Tieshan Wang
- School of Nuclear Science and Technology, Lanzhou University , Lanzhou, China
| | - Ziming Yang
- Environmental Sciences Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
| | - Hui Lin
- Environmental Sciences Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
| | - Dwayne A Elias
- Biosciences Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
| | - Eric M Pierce
- Environmental Sciences Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
| | - Liyuan Liang
- Environmental Sciences Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
- Biology and Soft Matter Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
| | - Tamar Barkay
- Department of Biochemistry and Microbiology, Rutgers University , New Brunswick, New Jersey 08901, United States
| | - Baohua Gu
- Environmental Sciences Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
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16
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Baesman SM, Miller LG, Wei JH, Cho Y, Matys ED, Summons RE, Welander PV, Oremland RS. Methane Oxidation and Molecular Characterization of Methanotrophs from a Former Mercury Mine Impoundment. Microorganisms 2015; 3:290-309. [PMID: 27682090 PMCID: PMC5023233 DOI: 10.3390/microorganisms3020290] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 06/01/2015] [Accepted: 06/11/2015] [Indexed: 12/22/2022] Open
Abstract
The Herman Pit, once a mercury mine, is an impoundment located in an active geothermal area. Its acidic waters are permeated by hundreds of gas seeps. One seep was sampled and found to be composed of mostly CO2 with some CH4 present. The δ13CH4 value suggested a complex origin for the methane: i.e., a thermogenic component plus a biological methanogenic portion. The relatively 12C-enriched CO2 suggested a reworking of the ebullitive methane by methanotrophic bacteria. Therefore, we tested bottom sediments for their ability to consume methane by conducting aerobic incubations of slurried materials. Methane was removed from the headspace of live slurries, and subsequent additions of methane resulted in faster removal rates. This activity could be transferred to an artificial, acidic medium, indicating the presence of acidophilic or acid-tolerant methanotrophs, the latter reinforced by the observation of maximum activity at pH = 4.5 with incubated slurries. A successful extraction of sterol and hopanoid lipids characteristic of methanotrophs was achieved, and their abundances greatly increased with increased sediment methane consumption. DNA extracted from methane-oxidizing enrichment cultures was amplified and sequenced for pmoA genes that aligned with methanotrophic members of the Gammaproteobacteria. An enrichment culture was established that grew in an acidic (pH 4.5) medium via methane oxidation.
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Affiliation(s)
| | | | - Jeremy H Wei
- Department of Earth System Science, Stanford University, Stanford, CA 94305, USA.
| | - Yirang Cho
- Department of Earth System Science, Stanford University, Stanford, CA 94305, USA.
| | - Emily D Matys
- Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
| | - Roger E Summons
- Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
| | - Paula V Welander
- Department of Earth System Science, Stanford University, Stanford, CA 94305, USA.
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17
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Mercury resistance and mercuric reductase activities and expression among chemotrophic thermophilic Aquificae. Appl Environ Microbiol 2012; 78:6568-75. [PMID: 22773655 DOI: 10.1128/aem.01060-12] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mercury (Hg) resistance (mer) by the reduction of mercuric to elemental Hg is broadly distributed among the Bacteria and Archaea and plays an important role in Hg detoxification and biogeochemical cycling. MerA is the protein subunit of the homodimeric mercuric reductase (MR) enzyme, the central function of the mer system. MerA sequences in the phylum Aquificae form the deepest-branching lineage in Bayesian phylogenetic reconstructions of all known MerA homologs. We therefore hypothesized that the merA homologs in two thermophilic Aquificae, Hydrogenobaculum sp. strain Y04AAS1 (AAS1) and Hydrogenivirga sp. strain 128-5-R1-1 (R1-1), specified Hg resistance. Results supported this hypothesis, because strains AAS1 and R1-1 (i) were resistant to >10 μM Hg(II), (ii) transformed Hg(II) to Hg(0) during cellular growth, and (iii) possessed Hg-dependent NAD(P)H oxidation activities in crude cell extracts that were optimal at temperatures corresponding with the strains' optimal growth temperatures, 55°C for AAS1 and 70°C for R1-1. While these characteristics all conformed with the mer system paradigm, expression of the Aquificae mer operons was not induced by exposure to Hg(II) as indicated by unity ratios of merA transcripts, normalized to gyrA transcripts for hydrogen-grown AAS1 cultures, and by similar MR specific activities in thiosulfate-grown cultures with and without Hg(II). The Hg(II)-independent expression of mer in the deepest-branching lineage of MerA from bacteria whose natural habitats are Hg-rich geothermal environments suggests that regulated expression of mer was a later innovation likely in environments where microorganisms were intermittently exposed to toxic concentrations of Hg.
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