8 results on '"Xia, Lu"'
Search Results
2. Stepwise Reduction Approach Reveals Mercury Competitive Binding and Exchange Reactions within Natural Organic Matter and Mixed Organic Ligands
- Author
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Liyuan Liang, Jiating Zhao, Eddy Y. Zeng, Xia Lu, Xujun Liang, and Baohua Gu
- Subjects
Mercuric ion ,Chemistry ,Kinetics ,Inorganic chemistry ,chemistry.chemical_element ,Mercury ,General Chemistry ,010501 environmental sciences ,Ligands ,Binding, Competitive ,01 natural sciences ,Natural organic matter ,Mercury (element) ,Competitive binding ,Dissolved organic carbon ,Environmental Chemistry ,Water Pollutants, Chemical ,0105 earth and related environmental sciences - Abstract
The kinetics of mercuric ion (Hg2+) binding with heterogeneous naturally dissolved organic matter (DOM) has been hypothesized to result from competitive interactions among different organic ligands...
- Published
- 2019
3. Mercury Uptake by Desulfovibrio desulfuricans ND132: Passive or Active?
- Author
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Alexander Johs, Eric M. Pierce, Baohua Gu, Jerry M. Parks, Xia Lu, Lijie Zhang, Dale A. Pelletier, and Jing An
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biology ,chemistry.chemical_element ,Mercury ,General Chemistry ,Methylation ,Methylmercury Compounds ,010501 environmental sciences ,Spheroplast ,Desulfovibrio desulfuricans ,biology.organism_classification ,01 natural sciences ,Mercury (element) ,chemistry ,Biochemistry ,Competitive binding ,Mercury uptake ,Environmental Chemistry ,Sulfhydryl Compounds ,Electrochemical gradient ,Bacteria ,0105 earth and related environmental sciences - Abstract
Recent studies have identified HgcAB proteins as being responsible for mercury [Hg(II)] methylation by certain anaerobic microorganisms. However, it remains controversial whether microbes take up Hg(II) passively or actively. Here, we examine the dynamics of concurrent Hg(II) adsorption, uptake, and methylation by both viable and inactivated cells (heat-killed or starved) or spheroplasts of the sulfate-reducing bacterium Desulfovibrio desulfuricans ND132 in laboratory incubations. We show that, without addition of thiols,60% of the added Hg(II) (25 nM) was taken up passively in 48 h by live and inactivated cells and also by cells treated with the proton gradient uncoupler, carbonylcyanide-3-chlorophenylhydrazone (CCCP). Inactivation abolished Hg(II) methylation, but the cells continued taking up Hg(II), likely through competitive binding or ligand exchange of Hg(II) by intracellular proteins or thiol-containing cellular components. Similarly, treatment with CCCP impaired the ability of spheroplasts to methylate Hg(II) but did not stop Hg(II) uptake. Spheroplasts showed a greater capacity to adsorb Hg(II) than whole cells, and the level of cytoplasmic membrane-bound Hg(II) correlated well with MeHg production, as Hg(II) methylation is associated with cytoplasmic HgcAB. Our results indicate that active metabolism is not required for cellular Hg(II) uptake, thereby providing an improved understanding of Hg(II) bioavailability for methylation.
- Published
- 2019
4. Mercury Sorption and Desorption on Organo-Mineral Particulates as a Source for Microbial Methylation
- Author
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Xia Lu, Shan Wu, Lijie Zhang, Baohua Gu, Linduo Zhao, and Eric M. Pierce
- Subjects
Minerals ,Microorganism ,chemistry.chemical_element ,Sediment ,Sorption ,Mercury ,General Chemistry ,Methylmercury Compounds ,010501 environmental sciences ,Particulates ,Hematite ,Contamination ,Methylation ,01 natural sciences ,Mercury (element) ,chemistry ,Environmental chemistry ,visual_art ,Desorption ,visual_art.visual_art_medium ,Environmental Chemistry ,Desulfovibrio desulfuricans ,0105 earth and related environmental sciences - Abstract
In natural freshwater and sediments, mercuric mercury (Hg(II)) is largely associated with particulate minerals and organics, but it remains unclear under what conditions particulates may become a sink or a source for Hg(II) and whether the particulate-bound Hg(II) is bioavailable for microbial uptake and methylation. In this study, we investigated Hg(II) sorption-desorption characteristics on three organo-coated hematite particulates and a Hg-contaminated natural sediment and evaluated the potential of particulate-bound Hg(II) for microbial methylation. Mercury rapidly sorbed onto particulates, especially the cysteine-coated hematite and sediment, with little desorption observed (0.1-4%). However, the presence of Hg-binding ligands, such as low-molecular-weight thiols and humic acids, resulted in up to 60% of Hg(II) desorption from the Hg-laden hematite particulates but
- Published
- 2019
5. Unraveling Microbial Communities Associated with Methylmercury Production in Paddy Soils
- Author
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Alexander Johs, Baohua Gu, Hang-Wei Hu, Xia Lu, Ji-Zheng He, Dan Sun, Yu-Rong Liu, and Li Bi
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0301 basic medicine ,China ,chemistry.chemical_element ,010501 environmental sciences ,01 natural sciences ,Soil ,03 medical and health sciences ,chemistry.chemical_compound ,Phylogenetics ,Botany ,Humans ,Environmental Chemistry ,Methylmercury ,Phylogeny ,0105 earth and related environmental sciences ,biology ,Microbiota ,Mercury ,General Chemistry ,Methylmercury Compounds ,biology.organism_classification ,Mercury (element) ,030104 developmental biology ,chemistry ,Metagenomics ,Soil water ,Paddy field ,Bacteria ,Geobacter - Abstract
Rice consumption is now recognized as an important pathway of human exposure to the neurotoxin methylmercury (MeHg), particularly in countries where rice is a staple food. Although the discovery of a two-gene cluster hgcAB has linked Hg methylation to several phylogenetically diverse groups of anaerobic microorganisms converting inorganic mercury (Hg) to MeHg, the prevalence and diversity of Hg methylators in microbial communities of rice paddy soils remain unclear. We characterized the abundance and distribution of hgcAB genes using third-generation PacBio long-read sequencing and Illumina short-read metagenomic sequencing, in combination with quantitative PCR analyses in several mine-impacted paddy soils from southwest China. Both Illumina and PacBio sequencing analyses revealed that Hg methylating communities were dominated by iron-reducing bacteria (i.e., Geobacter) and methanogens, with a relatively low abundance of hgcA+ sulfate-reducing bacteria in the soil. A positive correlation was observed betw...
- Published
- 2018
6. Anaerobic Mercury Methylation and Demethylation by Geobacter bemidjiensis Bem
- Author
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Alexander Johs, Liyuan Liang, Tamar Barkay, Xia Lu, Hui Lin, Dwayne A. Elias, Baohua Gu, Eric M. Pierce, Tieshan Wang, Yu-Rong Liu, Ziming Yang, and Linduo Zhao
- Subjects
0301 basic medicine ,Iron ,030106 microbiology ,Lyases ,010501 environmental sciences ,Methylation ,01 natural sciences ,03 medical and health sciences ,chemistry.chemical_compound ,Environmental Chemistry ,Anaerobiosis ,Cysteine ,Methylmercury ,0105 earth and related environmental sciences ,Demethylation ,Geobacter bemidjiensis ,biology ,Mercury ,General Chemistry ,Methylmercury Compounds ,biology.organism_classification ,Anoxic waters ,Biodegradation, Environmental ,chemistry ,Environmental chemistry ,Bioaccumulation ,Environmental Pollutants ,Anaerobic bacteria ,Geobacter ,Oxidoreductases ,Oxidation-Reduction ,Bacteria - 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.
- Published
- 2016
7. Anaerobic Mercury Methylation and Demethylation by Geobacter bemidjiensis Bem.
- Author
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Xia Lu, Yurong Liu, Johs, Alexander, Linduo Zhao, Tieshan Wang, Ziming Yang, Hui Lin, Elias, Dwayne A., Pierce, Eric M., Liyuan Liang, Barkay, Tamar, and Baohua Gu
- Subjects
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METHYLMERCURY , *GEOBACTER , *ANAEROBIC microorganisms , *NEUROTOXICOLOGY , *CHEMICAL decomposition , *ANOXIC waters - 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. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
8. Response to Comment on "Anaerobic Mercury Methylation and Demethylation by Geobacter Bemidjiensis Bern".
- Author
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Xia Lu, Yurong Liu, Alexander Johs, Linduo Zhao, Tieshan Wang, Ziming Yang, Hui Lin, Elias, Dwayne A., Pierce, Eric M., Liyuan Liang, Barkay, Tamar, and Baohua Gu
- Subjects
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ANAEROBIC bacteria , *MERCURY , *METHYLATION , *GEOBACTER , *NEUROTOXICOLOGY - Published
- 2016
- Full Text
- View/download PDF
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