1
|
Chang E, Lammers LN, Pallud C. High-affinity amide-lanthanide adsorption to gram-positive soil bacteria. ENVIRONMENTAL MICROBIOLOGY REPORTS 2023; 15:417-421. [PMID: 37150598 PMCID: PMC10472515 DOI: 10.1111/1758-2229.13162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Accepted: 04/27/2023] [Indexed: 05/09/2023]
Abstract
The gram-positive soil bacterium, Arthrobacter nicotianae, uses multiple organic acid functional groups to adsorb lanthanides onto its cell surface. At relevant soil pH conditions of 4.0-6.0, many of these functional groups are de-protonated and available for cation sorption and metal immobilization. However, among the plethora of naturally occurring site types, A. nicotianae is shown to possess high-affinity amide and phosphate sites that disproportionately affect lanthanide adsorption to the cell wall. We quantify neodymium (Nd)-selective site types, reporting an amide-Nd stability constant of log10 K = 6.41 ± 0.23 that is comparable to sorption via phosphate-based moieties. These sites are two to three orders of magnitude more selective for Nd than the adsorption of divalent metals to ubiquitous carboxyl-based moieties. This implies the importance of lanthanide biosorption in the context of metal transport in subsurface systems despite trace concentrations of lanthanides found in the natural environment.
Collapse
Affiliation(s)
- Elliot Chang
- Department of Environmental Science, Policy, and ManagementUniversity of California – BerkeleyBerkeleyCaliforniaUSA
| | - Laura N. Lammers
- Department of Environmental Science, Policy, and ManagementUniversity of California – BerkeleyBerkeleyCaliforniaUSA
- Energy Geosciences DivisionE.O. Lawrence Berkeley National LaboratoryBerkeleyCaliforniaUSA
| | - Céline Pallud
- Department of Environmental Science, Policy, and ManagementUniversity of California – BerkeleyBerkeleyCaliforniaUSA
| |
Collapse
|
2
|
Zhu T, Zeng Q, Zhao C, Wen Y, Li S, Li F, Lan T, Yang Y, Liu N, Sun Q, Liao J. Extracellular biomineralization of uranium and its toxicity alleviation to Bacillus thuringiensis X-27. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2023; 261:107126. [PMID: 36805950 DOI: 10.1016/j.jenvrad.2023.107126] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 01/19/2023] [Accepted: 02/01/2023] [Indexed: 06/18/2023]
Abstract
Uranium biomineralization can slow uranium migration in the environment and thus prevent it from further contaminating the surroundings. Investigations into the uranium species, pH, inorganic phosphate (Pi) concentration, and microbial viability during biomineralization by microorganisms are crucial for understanding the mineralization mechanism. In this study, Bacillus thuringiensis X-27 was isolated from soil contaminated with uranium and was used to investigate the formation process of uranium biominerals induced by X-27. The results showed that as biomineralization proceeded, amorphous uranium-containing deposits were generated and transformed into crystalline minerals outside cells, increasing the overall concentration of uramphite. This is a cumulative rather than abrupt process. Notably, B. thuringiensis X-27 precipitated uranium outside the cell surface within 0.5 h, while the release of Pi into the extracellular environment and the change of pH to alkalescence further promoted the formation of uramphite. In addition, cell viability determination showed that the U(VI) biomineralization induced by B. thuringiensis X-27 was instrumental in alleviating the toxicity of U(VI) to cells. This work offers insight into the mechanism of U(VI) phosphate biomineralization and is a reference for bioremediation-related studies.
Collapse
Affiliation(s)
- Ting Zhu
- Key Laboratory of Radiation Physics and Technology of the Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China; Key Laboratory of Bio-resources & Eco-environment of the Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610064, PR China
| | - Qian Zeng
- Key Laboratory of Radiation Physics and Technology of the Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China
| | - Changsong Zhao
- Key Laboratory of Radiation Physics and Technology of the Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China; Key Laboratory of Bio-resources & Eco-environment of the Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610064, PR China
| | - Yufeng Wen
- Department of Life Sciences, Jilin University, Street Qianjin 2699, Changchun, 130012, PR China
| | - Shangqing Li
- Department of Biological Sciences, Xi'an Jiaotong-Liverpool University, Suzhou, 215000, PR China
| | - Feize Li
- Key Laboratory of Radiation Physics and Technology of the Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China
| | - Tu Lan
- Key Laboratory of Radiation Physics and Technology of the Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China
| | - Yuanyou Yang
- Key Laboratory of Radiation Physics and Technology of the Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China
| | - Ning Liu
- Key Laboratory of Radiation Physics and Technology of the Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China
| | - Qun Sun
- Key Laboratory of Bio-resources & Eco-environment of the Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610064, PR China.
| | - Jiali Liao
- Key Laboratory of Radiation Physics and Technology of the Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China.
| |
Collapse
|
3
|
Ruiz-Fresneda MA, Martinez-Moreno MF, Povedano-Priego C, Morales-Hidalgo M, Jroundi F, Merroun ML. Impact of microbial processes on the safety of deep geological repositories for radioactive waste. Front Microbiol 2023; 14:1134078. [PMID: 37007474 PMCID: PMC10062484 DOI: 10.3389/fmicb.2023.1134078] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Accepted: 02/27/2023] [Indexed: 03/18/2023] Open
Abstract
To date, the increasing production of radioactive waste due to the extensive use of nuclear power is becoming a global environmental concern for society. For this reason, many countries have been considering the use of deep geological repositories (DGRs) for the safe disposal of this waste in the near future. Several DGR designs have been chemically, physically, and geologically well characterized. However, less is known about the influence of microbial processes for the safety of these disposal systems. The existence of microorganisms in many materials selected for their use as barriers for DGRs, including clay, cementitious materials, or crystalline rocks (e.g., granites), has previously been reported. The role that microbial processes could play in the metal corrosion of canisters containing radioactive waste, the transformation of clay minerals, gas production, and the mobility of the radionuclides characteristic of such residues is well known. Among the radionuclides present in radioactive waste, selenium (Se), uranium (U), and curium (Cm) are of great interest. Se and Cm are common components of the spent nuclear fuel residues, mainly as 79Se isotope (half-life 3.27 × 105 years), 247Cm (half-life: 1.6 × 107 years) and 248Cm (half-life: 3.5 × 106 years) isotopes, respectively. This review presents an up-to-date overview about how microbes occurring in the surroundings of a DGR may influence their safety, with a particular focus on the radionuclide-microbial interactions. Consequently, this paper will provide an exhaustive understanding about the influence of microorganisms in the safety of planned radioactive waste repositories, which in turn might improve their implementation and efficiency.
Collapse
|
4
|
Mijnendonckx K, Rogiers T, Giménez Del Rey FJ, Merroun ML, Williamson A, Ali MM, Charlier D, Leys N, Boon N, Van Houdt R. PrsQ 2, a small periplasmic protein involved in increased uranium resistance in the bacterium Cupriavidus metallidurans. JOURNAL OF HAZARDOUS MATERIALS 2023; 444:130410. [PMID: 36413896 DOI: 10.1016/j.jhazmat.2022.130410] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 11/10/2022] [Accepted: 11/14/2022] [Indexed: 06/16/2023]
Abstract
Uranium contamination is a widespread problem caused by natural and anthropogenic activities. Although microorganisms thrive in uranium-contaminated environments, little is known about the actual molecular mechanisms mediating uranium resistance. Here, we investigated the resistance mechanisms driving the adaptation of Cupriavidus metallidurans NA4 to toxic uranium concentrations. We selected a spontaneous mutant able to grow in the presence of 1 mM uranyl nitrate compared to 250 µM for the parental strain. The increased uranium resistance was acquired via the formation of periplasmic uranium-phosphate precipitates facilitated by the increased expression of a genus-specific small periplasmic protein, PrsQ2, regulated as non-cognate target of the CzcS2-CzcR2 two-component system. This study shows that bacteria can adapt to toxic uranium concentrations and explicates the complete genetic circuit behind the adaptation.
Collapse
Affiliation(s)
- Kristel Mijnendonckx
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium.
| | - Tom Rogiers
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium.
| | - Francisco J Giménez Del Rey
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium; Research Group of Microbiology, Department of Bioengineering Sciences, Vrije Universiteit Brussel, Brussels, Belgium.
| | - Mohamed L Merroun
- Campus Fuentenueva, Department of Microbiology, University of Granada, Granada, Spain.
| | - Adam Williamson
- Center for Microbial Ecology and Technology, UGent, Ghent, Belgium.
| | - Md Muntasir Ali
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium.
| | - Daniel Charlier
- Research Group of Microbiology, Department of Bioengineering Sciences, Vrije Universiteit Brussel, Brussels, Belgium.
| | - Natalie Leys
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium.
| | - Nico Boon
- Center for Microbial Ecology and Technology, UGent, Ghent, Belgium.
| | - Rob Van Houdt
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium.
| |
Collapse
|
5
|
Zeng Q, Zhu T, Wen Y, Li F, Cheng Y, Chen S, Lan T, Yang Y, Liao J, Sun Q, Liu N. The dynamic behavior and mechanism of uranium (VI) biomineralization in Enterobacter sp. X57. CHEMOSPHERE 2022; 298:134196. [PMID: 35276103 DOI: 10.1016/j.chemosphere.2022.134196] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Revised: 02/22/2022] [Accepted: 03/01/2022] [Indexed: 06/14/2023]
Abstract
The important role of microbes in the biomineralization and migration behavior of uranium in the field of environmental chemistry has been well emphasized in previous work. However, limited work on mineralization processes of indigenous microorganism has prevented us from a deeper understanding of the process and mechanisms of uranium biomineralization. In this work, the dynamic process and mechanism of uranium biomineralization in Enterobacter sp. X57, a novel uranium-tolerant microorganism separated from uranium contaminated soil, were systematically investigated. Enterobacter sp. X57 can induce intracellular mineralization of U (VI) to Uramphite (NH4UO2PO4·3H2O) under neutral conditions by alkaline phosphatase. In this biomineralization process, soluble U (VI) first bonded with the amino and phosphate groups on the plasma membrane, providing initial nucleation site for the formation of U (VI) biominerals. Then the impairment of cell barrier function and the enhancement of alkaline phosphatase metabolism occurred with the accumulation of uranium in cells, creating a possible pathway for soluble U (VI) to diffuse into the cell and be further mineralized into U (VI)-phosphate minerals. All the results revealed that the intracellular biomineralization of uranium by Enterobacter sp. X57 was a combined result of biosorption, intracellular accumulation and phosphatase metabolism. These findings may contribute to a better understanding of uranium biomineralization behavior and mechanism of microorganisms, as well as possible in-situ bioremediation strategies for uranium by indigenous microorganisms.
Collapse
Affiliation(s)
- Qian Zeng
- Key Laboratory of Radiation Physics and Technology of the Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China
| | - Ting Zhu
- Key Laboratory of Radiation Physics and Technology of the Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China; Key Laboratory of Biological Resource and Ecological Environment of the Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610064, PR China
| | - Yufeng Wen
- Department of Life Sciences, Jilin University, Street Qianjin 2699, Changchun, 130012, PR China
| | - Feize Li
- Key Laboratory of Radiation Physics and Technology of the Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China
| | - Yanxia Cheng
- Key Laboratory of Radiation Physics and Technology of the Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China
| | - Shunzhang Chen
- Key Laboratory of Radiation Physics and Technology of the Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China
| | - Tu Lan
- Key Laboratory of Radiation Physics and Technology of the Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China
| | - Yuanyou Yang
- Key Laboratory of Radiation Physics and Technology of the Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China
| | - Jiali Liao
- Key Laboratory of Radiation Physics and Technology of the Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China.
| | - Qun Sun
- Key Laboratory of Biological Resource and Ecological Environment of the Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610064, PR China
| | - Ning Liu
- Key Laboratory of Radiation Physics and Technology of the Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China
| |
Collapse
|
6
|
Rogiers T, Van Houdt R, Williamson A, Leys N, Boon N, Mijnendonckx K. Molecular Mechanisms Underlying Bacterial Uranium Resistance. Front Microbiol 2022; 13:822197. [PMID: 35359714 PMCID: PMC8963506 DOI: 10.3389/fmicb.2022.822197] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 01/27/2022] [Indexed: 11/16/2022] Open
Abstract
Environmental uranium pollution due to industries producing naturally occurring radioactive material or nuclear accidents and releases is a global concern. Uranium is hazardous for ecosystems as well as for humans when accumulated through the food chain, through contaminated groundwater and potable water sources, or through inhalation. In particular, uranium pollution pressures microbial communities, which are essential for healthy ecosystems. In turn, microorganisms can influence the mobility and toxicity of uranium through processes like biosorption, bioreduction, biomineralization, and bioaccumulation. These processes were characterized by studying the interaction of different bacteria with uranium. However, most studies unraveling the underlying molecular mechanisms originate from the last decade. Molecular mechanisms help to understand how bacteria interact with radionuclides in the environment. Furthermore, knowledge on these underlying mechanisms could be exploited to improve bioremediation technologies. Here, we review the current knowledge on bacterial uranium resistance and how this could be used for bioremediation applications.
Collapse
Affiliation(s)
- Tom Rogiers
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium
- Center for Microbial Ecology and Technology, Ghent University, Ghent, Belgium
| | - Rob Van Houdt
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium
| | - Adam Williamson
- Centre Etudes Nucléaires de Bordeaux Gradignan (CENBG), Bordeaux, France
| | - Natalie Leys
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium
| | - Nico Boon
- Center for Microbial Ecology and Technology, Ghent University, Ghent, Belgium
| | - Kristel Mijnendonckx
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium
- *Correspondence: Kristel Mijnendonckx,
| |
Collapse
|
7
|
Gallois N, Alpha-Bazin B, Bremond N, Ortet P, Barakat M, Piette L, Mohamad Ali A, Lemaire D, Legrand P, Theodorakopoulos N, Floriani M, Février L, Den Auwer C, Arnoux P, Berthomieu C, Armengaud J, Chapon V. Discovery and characterization of UipA, a uranium- and iron-binding PepSY protein involved in uranium tolerance by soil bacteria. THE ISME JOURNAL 2022; 16:705-716. [PMID: 34556817 PMCID: PMC8857325 DOI: 10.1038/s41396-021-01113-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 09/01/2021] [Accepted: 09/08/2021] [Indexed: 02/08/2023]
Abstract
Uranium is a naturally occurring radionuclide. Its redistribution, primarily due to human activities, can have adverse effects on human and non-human biota, which poses environmental concerns. The molecular mechanisms of uranium tolerance and the cellular response induced by uranium exposure in bacteria are not yet fully understood. Here, we carried out a comparative analysis of four actinobacterial strains isolated from metal and radionuclide-rich soils that display contrasted uranium tolerance phenotypes. Comparative proteogenomics showed that uranyl exposure affects 39-47% of the total proteins, with an impact on phosphate and iron metabolisms and membrane proteins. This approach highlighted a protein of unknown function, named UipA, that is specific to the uranium-tolerant strains and that had the highest positive fold-change upon uranium exposure. UipA is a single-pass transmembrane protein and its large C-terminal soluble domain displayed a specific, nanomolar binding affinity for UO22+ and Fe3+. ATR-FTIR and XAS-spectroscopy showed that mono and bidentate carboxylate groups of the protein coordinated both metals. The crystal structure of UipA, solved in its apo state and bound to uranium, revealed a tandem of PepSY domains in a swapped dimer, with a negatively charged face where uranium is bound through a set of conserved residues. This work reveals the importance of UipA and its PepSY domains in metal binding and radionuclide tolerance.
Collapse
Affiliation(s)
- Nicolas Gallois
- grid.5399.60000 0001 2176 4817Aix Marseille Université, CEA, CNRS, BIAM, 13108 Saint Paul-Lez-Durance, France
| | - Béatrice Alpha-Bazin
- grid.5583.b0000 0001 2299 8025Département Médicaments et Technologies pour la Santé (DMTS), Université Paris-Saclay, CEA, INRAE, SPI, 30200 Bagnols-sur-Cèze, France
| | - Nicolas Bremond
- grid.5399.60000 0001 2176 4817Aix Marseille Université, CEA, CNRS, BIAM, 13108 Saint Paul-Lez-Durance, France
| | - Philippe Ortet
- grid.5399.60000 0001 2176 4817Aix Marseille Université, CEA, CNRS, BIAM, 13108 Saint Paul-Lez-Durance, France
| | - Mohamed Barakat
- grid.5399.60000 0001 2176 4817Aix Marseille Université, CEA, CNRS, BIAM, 13108 Saint Paul-Lez-Durance, France
| | - Laurie Piette
- grid.5399.60000 0001 2176 4817Aix Marseille Université, CEA, CNRS, BIAM, 13108 Saint Paul-Lez-Durance, France
| | - Abbas Mohamad Ali
- grid.5399.60000 0001 2176 4817Aix Marseille Université, CEA, CNRS, BIAM, 13108 Saint Paul-Lez-Durance, France
| | - David Lemaire
- grid.5399.60000 0001 2176 4817Aix Marseille Université, CEA, CNRS, BIAM, 13108 Saint Paul-Lez-Durance, France
| | - Pierre Legrand
- grid.426328.9Synchrotron SOLEIL. L’Orme des Merisiers Saint-Aubin. BP 48, 91192 Gif-sur-Yvette, France
| | - Nicolas Theodorakopoulos
- grid.5399.60000 0001 2176 4817Aix Marseille Université, CEA, CNRS, BIAM, 13108 Saint Paul-Lez-Durance, France ,grid.418735.c0000 0001 1414 6236IRSN, PSE-ENV/SRTE/LR2T, B.P. 3, 13115 Saint Paul-lez-Durance, Cedex France
| | - Magali Floriani
- grid.418735.c0000 0001 1414 6236IRSN, PSE-ENV/SRTE/LECO, B.P. 3, 13115 Saint Paul-lez-Durance, Cedex France
| | - Laureline Février
- grid.418735.c0000 0001 1414 6236IRSN, PSE-ENV/SRTE/LR2T, B.P. 3, 13115 Saint Paul-lez-Durance, Cedex France
| | - Christophe Den Auwer
- grid.462124.70000 0004 0384 8488Université Côte d’Azur, CNRS, ICN, 06108 Nice, France
| | - Pascal Arnoux
- grid.5399.60000 0001 2176 4817Aix Marseille Université, CEA, CNRS, BIAM, 13108 Saint Paul-Lez-Durance, France
| | - Catherine Berthomieu
- grid.5399.60000 0001 2176 4817Aix Marseille Université, CEA, CNRS, BIAM, 13108 Saint Paul-Lez-Durance, France
| | - Jean Armengaud
- grid.5583.b0000 0001 2299 8025Département Médicaments et Technologies pour la Santé (DMTS), Université Paris-Saclay, CEA, INRAE, SPI, 30200 Bagnols-sur-Cèze, France
| | - Virginie Chapon
- Aix Marseille Université, CEA, CNRS, BIAM, 13108, Saint Paul-Lez-Durance, France.
| |
Collapse
|
8
|
Rogiers T, Merroun ML, Williamson A, Leys N, Houdt RV, Boon N, Mijnendonckx K. Cupriavidus metallidurans NA4 actively forms polyhydroxybutyrate-associated uranium-phosphate precipitates. JOURNAL OF HAZARDOUS MATERIALS 2022; 421:126737. [PMID: 34388922 DOI: 10.1016/j.jhazmat.2021.126737] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 07/21/2021] [Accepted: 07/22/2021] [Indexed: 06/13/2023]
Abstract
Cupriavidus metallidurans is a model bacterium to study molecular metal resistance mechanisms and its use for the bioremediation of several metals has been shown. However, its mechanisms for radionuclide resistance are unexplored. We investigated the interaction with uranium and associated cellular response to uranium for Cupriavidus metallidurans NA4. Strain NA4 actively captured 98 ± 1% of the uranium in its biomass after growing 24 h in the presence of 100 µM uranyl nitrate. TEM HAADF-EDX microscopy confirmed intracellular uranium-phosphate precipitates that were mainly associated with polyhydroxybutyrate. Furthermore, whole transcriptome sequencing indicated a complex transcriptional response with upregulation of genes encoding general stress-related proteins and several genes involved in metal resistance. More in particular, gene clusters known to be involved in copper and silver resistance were differentially expressed. This study provides further insights into bacterial interactions with and their response to uranium. Our results could be promising for uranium bioremediation purposes with the multi-metal resistant bacterium C. metallidurans NA4.
Collapse
Affiliation(s)
- Tom Rogiers
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium; Center for Microbial Ecology and Technology (CMET), UGent, Ghent, Belgium.
| | | | - Adam Williamson
- Center for Microbial Ecology and Technology (CMET), UGent, Ghent, Belgium.
| | - Natalie Leys
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium.
| | - Rob Van Houdt
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium.
| | - Nico Boon
- Center for Microbial Ecology and Technology (CMET), UGent, Ghent, Belgium.
| | - Kristel Mijnendonckx
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium.
| |
Collapse
|
9
|
Zhong J, Hu X, Liu X, Cui X, Lv Y, Tang C, Zhang M, Li H, Qiu L, Sun W. Isolation and Identification of Uranium Tolerant Phosphate-Solubilizing Bacillus spp. and Their Synergistic Strategies to U(VI) Immobilization. Front Microbiol 2021; 12:676391. [PMID: 34326819 PMCID: PMC8313988 DOI: 10.3389/fmicb.2021.676391] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 05/03/2021] [Indexed: 11/13/2022] Open
Abstract
The remediation of uranium (U) through phosphate-solubilizing bacteria (PSB) is an emerging technique as well as an interesting phenomenon for transforming mobile U into stable minerals in the environment. While studies are well needed for in-depth understanding of the mechanism of U(VI) immobilization by PSB. In this study, two PSB were isolated from a U-tailing repository site. These bacterial strains (ZJ-1 and ZJ-3) were identified as Bacillus spp. by the sequence analysis of 16S ribosomal RNA (rRNA) genes. Incubation of PSB in liquid medium showed that the isolate ZJ-3 could solubilize more than 230 mg L-1 P from glycerol-3-phosphate and simultaneously removed over 70% of 50 mg L-1 U(VI) within 1 h. During this process, the rapid appearance of yellow precipitates was observed. The microscopic and spectroscopic analysis demonstrated that the precipitates were associated with U-phosphate compound in the form of saleeite-like substances. Besides, scanning electron microscopy coupled with energy-dispersive X-ray (SEM-EDS) and Fourier transform infrared spectroscopy (FTIR) analysis of the precipitates confirmed that the extracellular polymeric substances (EPS) might also play a key role in U sequestration. Furthermore, SEM and FTIR analysis revealed that part of U(VI) was adsorbed on the bacterial surface through cellular phosphate, hydroxy, carboxyl, and amide groups. This study provides new insights into the synergistic strategies enhancing U immobilization rates by Bacillus spp. that uses glycerol-3-phosphate as the phosphorus source, the process of which contributes to harmful pollutant biodegradation.
Collapse
Affiliation(s)
- Juan Zhong
- GRINM Resources and Environment Tech. Co., Ltd., Beijing, China.,National Engineering Laboratory of Biohydrometallurgy, GRINM Group Co., Ltd., Beijing, China.,GRIMAT Engineering Institute Co., Ltd., Beijing, China
| | - Xuewu Hu
- GRINM Resources and Environment Tech. Co., Ltd., Beijing, China.,National Engineering Laboratory of Biohydrometallurgy, GRINM Group Co., Ltd., Beijing, China.,School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing, China
| | - Xingyu Liu
- GRINM Resources and Environment Tech. Co., Ltd., Beijing, China.,National Engineering Laboratory of Biohydrometallurgy, GRINM Group Co., Ltd., Beijing, China
| | - Xinglan Cui
- GRINM Resources and Environment Tech. Co., Ltd., Beijing, China.,National Engineering Laboratory of Biohydrometallurgy, GRINM Group Co., Ltd., Beijing, China
| | - Ying Lv
- GRINM Resources and Environment Tech. Co., Ltd., Beijing, China.,National Engineering Laboratory of Biohydrometallurgy, GRINM Group Co., Ltd., Beijing, China
| | - Chuiyun Tang
- GRINM Resources and Environment Tech. Co., Ltd., Beijing, China.,National Engineering Laboratory of Biohydrometallurgy, GRINM Group Co., Ltd., Beijing, China
| | - Mingjiang Zhang
- GRINM Resources and Environment Tech. Co., Ltd., Beijing, China.,National Engineering Laboratory of Biohydrometallurgy, GRINM Group Co., Ltd., Beijing, China
| | - Hongxia Li
- GRINM Resources and Environment Tech. Co., Ltd., Beijing, China.,National Engineering Laboratory of Biohydrometallurgy, GRINM Group Co., Ltd., Beijing, China
| | - Lang Qiu
- Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou, China
| | - Weimin Sun
- Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou, China
| |
Collapse
|
10
|
Pinel-Cabello M, Jroundi F, López-Fernández M, Geffers R, Jarek M, Jauregui R, Link A, Vílchez-Vargas R, Merroun ML. Multisystem combined uranium resistance mechanisms and bioremediation potential of Stenotrophomonas bentonitica BII-R7: Transcriptomics and microscopic study. JOURNAL OF HAZARDOUS MATERIALS 2021; 403:123858. [PMID: 33264934 DOI: 10.1016/j.jhazmat.2020.123858] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 07/18/2020] [Accepted: 08/24/2020] [Indexed: 06/12/2023]
Abstract
The potential use of microorganisms in the bioremediation of U pollution has been extensively described. However, a lack of knowledge on molecular resistance mechanisms has become a challenge for the use of these technologies. We reported on the transcriptomic and microscopic response of Stenotrophomonas bentonitica BII-R7 exposed to 100 and 250 μM of U. Results showed that exposure to 100 μM displayed up-regulation of 185 and 148 genes during the lag and exponential phases, respectively, whereas 143 and 194 were down-regulated, out of 3786 genes (>1.5-fold change). Exposure to 250 μM of U showed up-regulation of 68 genes and down-regulation of 290 during the lag phase. Genes involved in cell wall and membrane protein synthesis, efflux systems and phosphatases were up-regulated under all conditions tested. Microscopic observations evidenced the formation of U-phosphate minerals at membrane and extracellular levels. Thus, a biphasic process is likely to occur: the increased cell wall would promote the biosorption of U to the cell surface and its precipitation as U-phosphate minerals enhanced by phosphatases. Transport systems would prevent U accumulation in the cytoplasm. These findings contribute to an understanding of how microbes cope with U toxicity, thus allowing for the development of efficient bioremediation strategies.
Collapse
Affiliation(s)
- M Pinel-Cabello
- Department of Microbiology, University of Granada, Campus Fuentenueva s/n, 18071, Granada, Spain.
| | - F Jroundi
- Department of Microbiology, University of Granada, Campus Fuentenueva s/n, 18071, Granada, Spain
| | - M López-Fernández
- Institute of Resource Ecology, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstraße 400, 01328, Dresden, Germany
| | - R Geffers
- Genome Analytics, Helmholtz Centre for Infection Research (HZI), 38124, Braunschweig, Germany
| | - M Jarek
- Genome Analytics, Helmholtz Centre for Infection Research (HZI), 38124, Braunschweig, Germany
| | - R Jauregui
- AgResearch Grasslands Research Centre, Tennent drive, Palmerston North, New Zealand
| | - A Link
- Department of Gastroenterology, Hepatology and Infectious Diseases, University of Magdeburg, Leipziger Str. 44.39120, Magdeburg, Germany
| | - R Vílchez-Vargas
- Department of Gastroenterology, Hepatology and Infectious Diseases, University of Magdeburg, Leipziger Str. 44.39120, Magdeburg, Germany
| | - M L Merroun
- Department of Microbiology, University of Granada, Campus Fuentenueva s/n, 18071, Granada, Spain
| |
Collapse
|
11
|
Rodriguez-Freire L, DeVore CL, El Hayek E, Berti D, Ali AMS, Lezama Pacheco JS, Blake JM, Spilde MN, Brearley AJ, Artyushkova K, Cerrato JM. Emerging investigator series: entrapment of uranium-phosphorus nanocrystals inside root cells of Tamarix plants from a mine waste site. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2021; 23:73-85. [PMID: 33325952 PMCID: PMC8479813 DOI: 10.1039/d0em00306a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We investigated the mechanisms of uranium (U) uptake by Tamarix (salt cedars) growing along the Rio Paguate, which flows throughout the Jackpile mine near Pueblo de Laguna, New Mexico. Tamarix were selected for this study due to the detection of U in the roots and shoots of field collected plants (0.6-58.9 mg kg-1), presenting an average bioconcentration factor greater than 1. Synchrotron-based micro X-ray fluorescence analyses of plant roots collected from the field indicate that the accumulation of U occurs in the cortex of the root. The mechanisms for U accumulation in the roots of Tamarix were further investigated in controlled-laboratory experiments where living roots of field plants were macerated for 24 h or 2 weeks in a solution containing 100 μM U. The U concentration in the solution decreased 36-59% after 24 h, and 49-65% in two weeks. Microscopic and spectroscopic analyses detected U precipitation in the root cell walls near the xylems of the roots, confirming the initial results from the field samples. High-resolution TEM was used to study the U fate inside the root cells, and needle-like U-P nanocrystals, with diameter <7 nm, were found entrapped inside vacuoles in cells. EXAFS shell-by-shell fitting suggest that U is associated with carbon functional groups. The preferable binding of U to the root cell walls may explain the U retention in the roots of Tamarix, followed by U-P crystal precipitation, and pinocytotic active transport and cellular entrapment. This process resulted in a limited translocation of U to the shoots in Tamarix plants. This study contributes to better understanding of the physicochemical mechanisms affecting the U uptake and accumulation by plants growing near contaminated sites.
Collapse
Affiliation(s)
- Lucia Rodriguez-Freire
- Department of Civil and Environmental Engineering, New Jersey Institute of Technology, Newark, New Jersey 07102, USA.
| | - Cherie L DeVore
- Department of Civil Engineering, MSC01 1070, University of New Mexico, Albuquerque, New Mexico 87131, USA
| | - Eliane El Hayek
- Department of Chemistry, MSC03 2060, University of New Mexico, Albuquerque, New Mexico 87131, USA
| | - Debora Berti
- Oceanography Department, Texas A&M University, College Station, Texas 77845, USA
| | - Abdul-Mehdi S Ali
- Department of Earth and Planetary Sciences, MSC03 2040, University of New Mexico, Albuquerque, New Mexico 87131, USA
| | - Juan S Lezama Pacheco
- Department of Environmental Earth System Science, Stanford University, Stanford, California 94305, USA
| | - Johanna M Blake
- Department of Chemistry, MSC03 2060, University of New Mexico, Albuquerque, New Mexico 87131, USA and U.S. Geological Survey, 6700 Edith Blvd NE, Albuquerque, New Mexico 87113, USA
| | - Michael N Spilde
- Department of Earth and Planetary Sciences, MSC03 2040, University of New Mexico, Albuquerque, New Mexico 87131, USA
| | - Adrian J Brearley
- Department of Earth and Planetary Sciences, MSC03 2040, University of New Mexico, Albuquerque, New Mexico 87131, USA
| | - Kateryna Artyushkova
- Department of Chemical and Biological Engineering, MSC01 1120, University of New Mexico, Albuquerque, New Mexico 87131, USA
| | - José M Cerrato
- Department of Civil Engineering, MSC01 1070, University of New Mexico, Albuquerque, New Mexico 87131, USA
| |
Collapse
|
12
|
Morrison KD, Zavarin M, Kersting AB, Begg JD, Mason HE, Balboni E, Jiao Y. Influence of Uranium Concentration and pH on U-Phosphate Biomineralization by Caulobacter OR37. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:1626-1636. [PMID: 33471994 DOI: 10.1021/acs.est.0c05437] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Uranium contamination of soils and groundwater in the United States represents a significant health risk and will require multiple remediation approaches. Microbial phosphatase activity coupled to the addition of an organic P source has recently been studied as a remediation strategy that provides an extended release of inorganic P (Pi) into U-contaminated sites, resulting in the precipitation of meta-autunite minerals. Previous laboratory- and field-based biomineralization studies have investigated environments with relatively high U concentrations (>20 μM). However, most contaminated sites have much lower U concentrations (<2 μM). The Environmental Protection Agency (EPA) limit for U in drinking water is 0.126 μM. Reaching this regulatory limit becomes challenging as U concentrations approach autunite solubility. We studied the precipitation of U(VI)-phosphate minerals by an environmental isolate of Caulobacter sp. (strain OR37) from an Oak Ridge, Tennessee, U-contaminated site. Abiotic U(VI) solubility experiments reveal that U(VI)-phosphate minerals do not form in the presence of excess Pi (500 μM) when U(VI) concentrations are <1 μM and pH is <5. When OR37 cells are reacted under the same conditions with Pi or glycerol-2-phosphate, U(VI)-phosphate mineral formation was observed, along with the formation of intracellular polyphosphate granules. These results show that bacteria provide supersaturated microenvironments needed for U(VI)-phosphate mineralization while hydrolyzing organic P sources. This provides a pathway to lower U concentrations to below EPA limits for drinking water.
Collapse
|
13
|
Gendy S, Chauhan A, Agarwal M, Pathak A, Rathore RS, Jaswal R. Is Long-Term Heavy Metal Exposure Driving Carriage of Antibiotic Resistance in Environmental Opportunistic Pathogens: A Comprehensive Phenomic and Genomic Assessment Using Serratia sp. SRS-8-S-2018. Front Microbiol 2020; 11:1923. [PMID: 32973703 PMCID: PMC7468404 DOI: 10.3389/fmicb.2020.01923] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Accepted: 07/21/2020] [Indexed: 12/04/2022] Open
Abstract
The carriage of both, heavy metal and antibiotic resistance appears to be a common trait in bacterial communities native to long-term contaminated habitats, including the Savannah River Site (SRS). There is widespread soil contamination at the SRS; a United States Department of Energy (DOE) facility with long-term contamination from past industrial and nuclear weapons production activities. To further evaluate the genomic and metabolic traits that underpin metal and antibiotic resistance, a robust mercury (Hg) and uranium (U)-resistant strain- SRS-8-S-2018, was isolated. Minimum inhibitory concentration of this strain revealed resistance to Hg (10 μg/ml) and U (5 mM), the two main heavy metal contaminants at the SRS. Metabolic assessment of strain SRS-8-S-2018 using Biolog metabolic fingerprinting analysis revealed preference for carbohydrate utilization followed by polymers, amino acids, carboxy acids, and esters; this physiological activity diminished when Hg stress was provided at 1 and 3 μg/ml and completely ceased at 5 μg/ml Hg, indicating that continued release of Hg will have negative metabolic impacts to even those microorganisms that possess high resistance ability. Development of antibiotic resistance in strain SRS-8-S-2018 was evaluated at a functional level using phenomics, which confirmed broad resistance against 70.8% of the 48 antibiotics tested. Evolutionary and adaptive traits of strain SRS-8-S-2018 were further assessed using genomics, which revealed the strain to taxonomically affiliate with Serratia marcescens species, possessing a genome size of 5,323,630 bp, 5,261 proteins (CDS), 55 genes for transfer RNA (tRNA), and an average G + C content of 59.48. Comparative genomics with closest taxonomic relatives revealed 360 distinct genes in SRS-8-S-2018, with multiple functions related to both, antibiotic and heavy metal resistance, which likely facilitates the strain’s survival in a metalliferous soil habitat. Comparisons drawn between the environmentally isolated Serratia SRS-8-S-2018 with 31 other strains revealed a closer functional association with medically relevant isolates suggesting that propensity of environmental Serratia isolates in acquiring virulence traits, as a function of long-term exposure to heavy metals, which is facilitating development, recruitment and proliferation of not only metal resistant genes (MRGs) but antibiotic resistant genes (ARGs), which can potentially trigger future bacterial pathogen outbreaks emanating from contaminated environmental habitats.
Collapse
Affiliation(s)
- Sherif Gendy
- School of Allied Health Sciences, Florida A&M University, Tallahassee, FL, United States
| | - Ashvini Chauhan
- Environmental Biotechnology Laboratory, School of the Environment, FSH Science Research Center, Florida A&M University, Tallahassee, FL, United States
| | - Meenakshi Agarwal
- Environmental Biotechnology Laboratory, School of the Environment, FSH Science Research Center, Florida A&M University, Tallahassee, FL, United States
| | - Ashish Pathak
- Environmental Biotechnology Laboratory, School of the Environment, FSH Science Research Center, Florida A&M University, Tallahassee, FL, United States
| | - Rajesh Singh Rathore
- Environmental Biotechnology Laboratory, School of the Environment, FSH Science Research Center, Florida A&M University, Tallahassee, FL, United States
| | - Rajneesh Jaswal
- Environmental Biotechnology Laboratory, School of the Environment, FSH Science Research Center, Florida A&M University, Tallahassee, FL, United States
| |
Collapse
|
14
|
Hurault L, Creff G, Hagège A, Santucci-Darmanin S, Pagnotta S, Farlay D, Den Auwer C, Pierrefite-Carle V, Carle GF. Uranium Effect on Osteocytic Cells In Vitro. Toxicol Sci 2020; 170:199-209. [PMID: 31120128 DOI: 10.1093/toxsci/kfz087] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Once absorbed in the body, natural uranium [U(VI)], a radionucleotide naturally present in the environment, is targeted to the skeleton which is the long-term storage organ. We and others have reported the U(VI) negative effects on osteoblasts (OB) and osteoclasts (OC), the main two cell types involved in bone remodeling. In the present work, we addressed the U(VI) effect on osteocytes (OST), the longest living bone cell type and the more numerous (> 90%). These cells, which are embedded in bone matrix and thus are the more prone to U(VI) long-term exposure, are now considered as the chief orchestrators of the bone remodeling process. Our results show that the cytotoxicity index of OST is close to 730 µM, which is about twice the one reported for OB and OC. However, despite this resistance potential, we observed that chronic U(VI) exposure as low as 5 µM led to a drastic decrease of the OST mineralization function. Gene expression analysis showed that this impairment could potentially be linked to an altered differentiation process of these cells. We also observed that U(VI) was able to trigger autophagy, a highly conserved survival mechanism. Extended X-ray absorption fine structure analysis at the U LIII edge of OST cells exposed to U(VI) unambiguously shows the formation of an uranyl phosphate phase in which the uranyl local structure is similar to the one present in Autunite. Thus, our results demonstrate for the first time that OST mineralization function can be affected by U(VI) exposure as low as 5 µM, suggesting that prolonged exposure could alter the central role of these cells in the bone environment.
Collapse
Affiliation(s)
- Lucile Hurault
- UMR E-4320 TIRO-MATOs CEA/DRF/BIAM, Université Nice Sophia Antipolis, Université Côte d'Azur 06107 Nice
| | - Gaelle Creff
- UMR7272 Institut de Chimie de Nice, Université Côte d'Azur, CNRS, Nice
| | - Agnès Hagège
- Institut des Sciences Analytiques, UMR 5280, Université de Lyon, CNRS, Université Claude Bernard Lyon 1, Lyon
| | - Sabine Santucci-Darmanin
- UMR E-4320 TIRO-MATOs CEA/DRF/BIAM, Université Nice Sophia Antipolis, Université Côte d'Azur 06107 Nice
| | - Sophie Pagnotta
- Centre Commun de Microscopie Appliquée, Université Nice Sophia Antipolis, Nice
| | | | | | - Valérie Pierrefite-Carle
- UMR E-4320 TIRO-MATOs CEA/DRF/BIAM, Université Nice Sophia Antipolis, Université Côte d'Azur 06107 Nice
| | - Georges F Carle
- UMR E-4320 TIRO-MATOs CEA/DRF/BIAM, Université Nice Sophia Antipolis, Université Côte d'Azur 06107 Nice
| |
Collapse
|
15
|
Tu H, Yuan G, Zhao C, Liu J, Li F, Yang J, Liao J, Yang Y, Liu N. U-phosphate biomineralization induced by Bacillus sp. dw-2 in the presence of organic acids. NUCLEAR ENGINEERING AND TECHNOLOGY 2019. [DOI: 10.1016/j.net.2019.03.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
16
|
Metagenomics-Guided Survey, Isolation, and Characterization of Uranium Resistant Microbiota from the Savannah River Site, USA. Genes (Basel) 2019; 10:genes10050325. [PMID: 31035394 PMCID: PMC6562407 DOI: 10.3390/genes10050325] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Revised: 04/19/2019] [Accepted: 04/24/2019] [Indexed: 11/17/2022] Open
Abstract
Despite the recent advancements in culturomics, isolation of the majority of environmental microbiota performing critical ecosystem services, such as bioremediation of contaminants, remains elusive. Towards this end, we conducted a metagenomics-guided comparative assessment of soil microbial diversity and functions present in uraniferous soils relative to those that grew in diffusion chambers (DC) or microbial traps (MT), followed by isolation of uranium (U) resistant microbiota. Shotgun metagenomic analysis performed on the soils used to establish the DC/MT chambers revealed Proteobacterial phyla and Burkholderia genus to be the most abundant among bacteria. The chamber-associated growth conditions further increased their abundances relative to the soils. Ascomycota was the most abundant fungal phylum in the chambers relative to the soils, with Penicillium as the most dominant genus. Metagenomics-based taxonomic findings completely mirrored the taxonomic composition of the retrieved isolates such that the U-resistant bacteria and fungi mainly belonged to Burkholderia and Penicillium species, thus confirming that the chambers facilitated proliferation and subsequent isolation of specific microbiota with environmentally relevant functions. Furthermore, shotgun metagenomic analysis also revealed that the gene classes for carbohydrate metabolism, virulence, and respiration predominated with functions related to stress response, membrane transport, and metabolism of aromatic compounds were also identified, albeit at lower levels. Of major note was the successful isolation of a potentially novel Penicillium species using the MT approach, as evidenced by whole genome sequence analysis and comparative genomic analysis, thus enhancing our overall understanding on the uranium cycling microbiota within the tested uraniferous soils.
Collapse
|
17
|
Park DM, Taffet MJ. Combinatorial Sensor Design in Caulobacter crescentus for Selective Environmental Uranium Detection. ACS Synth Biol 2019; 8:807-817. [PMID: 30897331 DOI: 10.1021/acssynbio.8b00484] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The ability to detect uranium (U) through environmental monitoring is of critical importance for informing water resource protection and nonproliferation efforts. While technologies exist for environmental U detection, wide-area environmental monitoring, i.e. sampling coverage over large areas not known to possess U contamination, remains a challenging prospect that necessitates the development of novel detection approaches. Herein, we describe the development of a whole-cell U sensor by integrating two functionally independent, native U-responsive two-component signaling systems (TCS), UzcRS and UrpRS, within an AND gate circuit in the bacterium Caulobacter crescentus. Through leverage of the distinct but imperfect selectivity profiles of both TCS, this combinatorial approach enabled greater selectivity relative to a prior biosensor developed with UzcRS alone; no cross-reactivity was observed with most common environmental metals (e.g, Fe, As, Cu, Ca, Mg, Cd, Cr, Al) or the U decay-chain product Th, and the selectivity against Zn and Pb was significantly improved. In addition, integration of the UzcRS signal amplifier protein UzcY within the AND gate circuit further enhanced overall sensitivity and selectivity for U. The functionality of the sensor in an environmental context was confirmed by detection of U concentrations as low as 1 μM in groundwater samples. The results highlight the value of a combinatorial approach for constructing whole-cell sensors for the selective detection of analytes for which there are no known evolved regulators.
Collapse
Affiliation(s)
- Dan M. Park
- Biosciences and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
| | - Michael J. Taffet
- Environmental Restoration Department (ERD), Operations and Business Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
| |
Collapse
|
18
|
Zhao X, Do H, Zhou Y, Li Z, Zhang X, Zhao S, Li M, Wu D. Rahnella sp. LRP3 induces phosphate precipitation of Cu (II) and its role in copper-contaminated soil remediation. JOURNAL OF HAZARDOUS MATERIALS 2019; 368:133-140. [PMID: 30669037 DOI: 10.1016/j.jhazmat.2019.01.029] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Revised: 01/10/2019] [Accepted: 01/11/2019] [Indexed: 06/09/2023]
Abstract
Microbially induced phosphate precipitation (MIPP) is an advanced bioremediation technology to immobilize heavy metals in soil. In this study, an indigenous bacterial strain LRP3, identified as Rahnella sp., was isolated from Cu-contaminated dark brown soil in the mining area. Strain LRP3 could produce phytase and alkaline phosphatase to degrade phytic acid, which released soluble phosphate to the bacterial culture. Due to the metabolism of bacterial growth, the pH value of bacterial culture was increased. The minimum inhibitory concentration of Cu (II) to bacterial growth in solution was up to 130 mg/L. The bacterial culture could rapidly precipitate Cu (II) in solution through MIPP. The analysis results of Scanning Electron Microscope-Energy Dispersive Spectroscopy (SEM-EDS), Fourier Transform-Infrared Spectrometer (FTIR), and X-ray Diffraction (XRD) revealed that the precipitate form by bacterial culture was rod-shaped Cu3(OH)3PO4 crystal with a diameter of 10 μm. The bacterial culture decreased the content of DTPA-Cu of 83 mg/kg soil in the soil by 58.2%, 61.5% and 75.8% after 5, 10 and 30 days of incubation, respectively, at the temperature of 25 °C. The results indicate that MIPP-based bioremediation by Rahnella sp. LRP3 is a practical, environmental friendly technology for the cleaning-up of copper-contaminated soil.
Collapse
Affiliation(s)
- Xingmin Zhao
- College of Resource and Environment, Key Laboratory of Soil Resource Sustainable Utilization for Jilin Province Commodity Grain Bases, Jilin Agricultural University, Changchun 130118, China
| | - HoaiThuong Do
- College of Resource and Environment, Key Laboratory of Soil Resource Sustainable Utilization for Jilin Province Commodity Grain Bases, Jilin Agricultural University, Changchun 130118, China
| | - Ye Zhou
- College of Resource and Environment, Key Laboratory of Soil Resource Sustainable Utilization for Jilin Province Commodity Grain Bases, Jilin Agricultural University, Changchun 130118, China
| | - Zhe Li
- College of Resource and Environment, Key Laboratory of Soil Resource Sustainable Utilization for Jilin Province Commodity Grain Bases, Jilin Agricultural University, Changchun 130118, China
| | - Xiufang Zhang
- College of Resource and Environment, Key Laboratory of Soil Resource Sustainable Utilization for Jilin Province Commodity Grain Bases, Jilin Agricultural University, Changchun 130118, China
| | - Shujie Zhao
- College of Resource and Environment, Key Laboratory of Soil Resource Sustainable Utilization for Jilin Province Commodity Grain Bases, Jilin Agricultural University, Changchun 130118, China
| | - Mingtang Li
- College of Resource and Environment, Key Laboratory of Soil Resource Sustainable Utilization for Jilin Province Commodity Grain Bases, Jilin Agricultural University, Changchun 130118, China.
| | - Di Wu
- College of Resource and Environment, Key Laboratory of Soil Resource Sustainable Utilization for Jilin Province Commodity Grain Bases, Jilin Agricultural University, Changchun 130118, China.
| |
Collapse
|
19
|
Tu H, Lan T, Yuan G, Zhao C, Liu J, Li F, Yang J, Liao J, Yang Y, Wang D, Liu N. The influence of humic substances on uranium biomineralization induced by Bacillus sp. dwc-2. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2019; 197:23-29. [PMID: 30502659 DOI: 10.1016/j.jenvrad.2018.11.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Revised: 11/15/2018] [Accepted: 11/21/2018] [Indexed: 06/09/2023]
Abstract
In this paper, the influence of humic acid (HA) and fulvic acid (FA) on biomineralization behaviour was evaluated. The results showed HA and FA did not obviously inhabit or promote the precipitation of U-phosphate minerals. The data from molecular dynamic simulation indicated that the free energy for the dissociation of uranyl the PO43- -uranyl was 202.49 kJ/mol, which was much larger than that form HA-uranyl (88.3 kJ/mol). These simulated results revealed the less competitiveness of HA and FA with PO43- for uranyl and explained why HA and FA had less impacted on the formation of U-phosphate minerals. However, the influence of HA/FA on the morphology was obvious, the microstructure of the bio-minerals changed from small particles to lamellar stacking structure with the addition of HA or FA. The findings of this study are helpful for us to gain a better understanding natural U-phosphate biomineralization behaviour.
Collapse
Affiliation(s)
- Hong Tu
- Key Laboratory of Radiation Physics and Technology (Sichuan University), Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China.
| | - Tu Lan
- Key Laboratory of Radiation Physics and Technology (Sichuan University), Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China; CAS Key Laboratory of Nuclear Radiation and Nuclear Energy Techniques, Multidisciplinary Initiative Centre, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, PR China.
| | - Guoyuan Yuan
- Key Laboratory of Radiation Physics and Technology (Sichuan University), Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China.
| | - Changsong Zhao
- Key Laboratory of Radiation Physics and Technology (Sichuan University), Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China.
| | - Jun Liu
- Key Laboratory of Radiation Physics and Technology (Sichuan University), Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China.
| | - Feize Li
- Key Laboratory of Radiation Physics and Technology (Sichuan University), Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China.
| | - Jijun Yang
- Key Laboratory of Radiation Physics and Technology (Sichuan University), Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China.
| | - Jiali Liao
- Key Laboratory of Radiation Physics and Technology (Sichuan University), Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China.
| | - Yuanyou Yang
- Key Laboratory of Radiation Physics and Technology (Sichuan University), Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China.
| | - Dongqi Wang
- CAS Key Laboratory of Nuclear Radiation and Nuclear Energy Techniques, Multidisciplinary Initiative Centre, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, PR China.
| | - Ning Liu
- Key Laboratory of Radiation Physics and Technology (Sichuan University), Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China.
| |
Collapse
|
20
|
Gallo G, Presta L, Perrin E, Gallo M, Marchetto D, Puglia AM, Fani R, Baldi F. Genomic traits of Klebsiella oxytoca DSM 29614, an uncommon metal-nanoparticle producer strain isolated from acid mine drainages. BMC Microbiol 2018; 18:198. [PMID: 30482178 PMCID: PMC6258164 DOI: 10.1186/s12866-018-1330-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Accepted: 10/29/2018] [Indexed: 12/24/2022] Open
Abstract
Background Klebsiella oxytoca DSM 29614 - isolated from acid mine drainages - grows anaerobically using Fe(III)-citrate as sole carbon and energy source, unlike other enterobacteria and K. oxytoca clinical isolates. The DSM 29614 strain is multi metal resistant and produces metal nanoparticles that are embedded in its very peculiar capsular exopolysaccharide. These metal nanoparticles were effective as antimicrobial and anticancer compounds, chemical catalysts and nano-fertilizers. Results The DSM 29614 strain genome was sequenced and analysed by a combination of in silico procedures. Comparative genomics, performed between 85 K. oxytoca representatives and K. oxytoca DSM 29614, revealed that this bacterial group has an open pangenome, characterized by a very small core genome (1009 genes, about 2%), a high fraction of unique (43,808 genes, about 87%) and accessory genes (5559 genes, about 11%). Proteins belonging to COG categories “Carbohydrate transport and metabolism” (G), “Amino acid transport and metabolism” (E), “Coenzyme transport and metabolism” (H), “Inorganic ion transport and metabolism” (P), and “membrane biogenesis-related proteins” (M) are particularly abundant in the predicted proteome of DSM 29614 strain. The results of a protein functional enrichment analysis - based on a previous proteomic analysis – revealed metabolic optimization during Fe(III)-citrate anaerobic utilization. In this growth condition, the observed high levels of Fe(II) may be due to different flavin metal reductases and siderophores as inferred form genome analysis. The presence of genes responsible for the synthesis of exopolysaccharide and for the tolerance to heavy metals was highlighted too. The inferred genomic insights were confirmed by a set of phenotypic tests showing specific metabolic capability in terms of i) Fe2+ and exopolysaccharide production and ii) phosphatase activity involved in precipitation of metal ion-phosphate salts. Conclusion The K. oxytoca DSM 29614 unique capabilities of using Fe(III)-citrate as sole carbon and energy source in anaerobiosis and tolerating diverse metals coincides with the presence at the genomic level of specific genes that can support i) energy metabolism optimization, ii) cell protection by the biosynthesis of a peculiar exopolysaccharide armour entrapping metal ions and iii) general and metal-specific detoxifying activities by different proteins and metabolites. Electronic supplementary material The online version of this article (10.1186/s12866-018-1330-5) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Giuseppe Gallo
- Laboratory of Molecular Microbiology and Biotechnology, Department of Biological, Chemical and Pharmaceutical Sciences and Technologies, Viale delle Scienze, ed. 16, 90128, Palermo, Italy.
| | - Luana Presta
- Laboratory of Microbial and Molecular Evolution, Department of Biology, University of Florence, Via Madonna del Piano 6, I-50019 Sesto F.no, Florence, Italy
| | - Elena Perrin
- Laboratory of Microbial and Molecular Evolution, Department of Biology, University of Florence, Via Madonna del Piano 6, I-50019 Sesto F.no, Florence, Italy
| | - Michele Gallo
- Dipartimento di Scienze Molecolari e Nanosistemi, University Cà Foscari Venezia, Via Torino 155, 30172, Mestre, Venezia, Italy
| | - Davide Marchetto
- Dipartimento di Scienze Molecolari e Nanosistemi, University Cà Foscari Venezia, Via Torino 155, 30172, Mestre, Venezia, Italy
| | - Anna Maria Puglia
- Laboratory of Molecular Microbiology and Biotechnology, Department of Biological, Chemical and Pharmaceutical Sciences and Technologies, Viale delle Scienze, ed. 16, 90128, Palermo, Italy
| | - Renato Fani
- Laboratory of Microbial and Molecular Evolution, Department of Biology, University of Florence, Via Madonna del Piano 6, I-50019 Sesto F.no, Florence, Italy
| | - Franco Baldi
- Dipartimento di Scienze Molecolari e Nanosistemi, University Cà Foscari Venezia, Via Torino 155, 30172, Mestre, Venezia, Italy
| |
Collapse
|
21
|
Kolhe N, Zinjarde S, Acharya C. Responses exhibited by various microbial groups relevant to uranium exposure. Biotechnol Adv 2018; 36:1828-1846. [PMID: 30017503 DOI: 10.1016/j.biotechadv.2018.07.002] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Revised: 07/08/2018] [Accepted: 07/09/2018] [Indexed: 11/28/2022]
Abstract
There is a strong interest in knowing how various microbial systems respond to the presence of uranium (U), largely in the context of bioremediation. There is no known biological role for uranium so far. Uranium is naturally present in rocks and minerals. The insoluble nature of the U(IV) minerals keeps uranium firmly bound in the earth's crust minimizing its bioavailability. However, anthropogenic nuclear reaction processes over the last few decades have resulted in introduction of uranium into the environment in soluble and toxic forms. Microbes adsorb, accumulate, reduce, oxidize, possibly respire, mineralize and precipitate uranium. This review focuses on the microbial responses to uranium exposure which allows the alteration of the forms and concentrations of uranium within the cell and in the local environment. Detailed information on the three major bioprocesses namely, biosorption, bioprecipitation and bioreduction exhibited by the microbes belonging to various groups and subgroups of bacteria, fungi and algae is provided in this review elucidating their intrinsic and engineered abilities for uranium removal. The survey also highlights the instances of the field trials undertaken for in situ uranium bioremediation. Advances in genomics and proteomics approaches providing the information on the regulatory and physiologically important determinants in the microbes in response to uranium challenge have been catalogued here. Recent developments in metagenomics and metaproteomics indicating the ecologically relevant traits required for the adaptation and survival of environmental microbes residing in uranium contaminated sites are also included. A comprehensive understanding of the microbial responses to uranium can facilitate the development of in situ U bioremediation strategies.
Collapse
Affiliation(s)
- Nilesh Kolhe
- Institute of Bioinformatics and Biotechnology, Savitribai Phule Pune University, Pune 411007, India; Molecular Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India
| | - Smita Zinjarde
- Institute of Bioinformatics and Biotechnology, Savitribai Phule Pune University, Pune 411007, India; Department of Microbiology, Savitribai Phule Pune University, Pune 411007, India.
| | - Celin Acharya
- Molecular Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India; Homi Bhabha National Institute, Anushakti Nagar, Trombay, Mumbai 400094, India.
| |
Collapse
|
22
|
Skouri-Panet F, Benzerara K, Cosmidis J, Férard C, Caumes G, De Luca G, Heulin T, Duprat E. In Vitro and in Silico Evidence of Phosphatase Diversity in the Biomineralizing Bacterium Ramlibacter tataouinensis. Front Microbiol 2018; 8:2592. [PMID: 29375498 PMCID: PMC5768637 DOI: 10.3389/fmicb.2017.02592] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 12/12/2017] [Indexed: 11/13/2022] Open
Abstract
Microbial phosphatase activity can trigger the precipitation of metal-phosphate minerals, a process called phosphatogenesis with global geochemical and environmental implications. An increasing diversity of phosphatases expressed by diverse microorganisms has been evidenced in various environments. However, it is challenging to link the functional properties of genomic repertoires of phosphatases with the phosphatogenesis capabilities of microorganisms. Here, we studied the betaproteobacterium Ramlibacter tataouinensis (Rta), known to biomineralize Ca-phosphates in the environment and the laboratory. We investigated the functional repertoire of this biomineralization process at the cell, genome and molecular level. Based on a mineralization assay, Rta is shown to hydrolyse the phosphoester bonds of a wide range of organic P molecules. Accordingly, its genome has an unusually high diversity of phosphatases: five genes belonging to two non-homologous families, phoD and phoX, were detected. These genes showed diverse predicted cis-regulatory elements. Moreover, they encoded proteins with diverse structural properties according to molecular models. Heterologously expressed PhoD and PhoX in Escherichia coli had different profiles of substrate hydrolysis. As evidenced for Rta cells, recombinant E. coli cells induced the precipitation of Ca-phosphate mineral phases, identified as poorly crystalline hydroxyapatite. The phosphatase genomic repertoire of Rta (containing phosphatases of both the PhoD and PhoX families) was previously evidenced as prevalent in marine oligotrophic environments. Interestingly, the Tataouine sand from which Rta was isolated showed similar P-depleted, but Ca-rich conditions. Overall, the diversity of phosphatases in Rta allows the hydrolysis of a broad range of organic P substrates and therefore the release of orthophosphates (inorganic phosphate) under diverse trophic conditions. Since the release of orthophosphates is key to the achievement of high saturation levels with respect to hydroxyapatite and the induction of phosphatogenesis, Rta appears as a particularly efficient driver of this process as shown experimentally.
Collapse
Affiliation(s)
- Fériel Skouri-Panet
- Centre National de la Recherche Scientifique, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Sorbonne Universités, UMR 7590, Muséum National d'Histoire Naturelle, Université Pierre et Marie Curie, IRD 206, Paris, France
| | - Karim Benzerara
- Centre National de la Recherche Scientifique, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Sorbonne Universités, UMR 7590, Muséum National d'Histoire Naturelle, Université Pierre et Marie Curie, IRD 206, Paris, France
| | - Julie Cosmidis
- Department of Geological Sciences, University of Colorado, Boulder, CO, United States
| | - Céline Férard
- Centre National de la Recherche Scientifique, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Sorbonne Universités, UMR 7590, Muséum National d'Histoire Naturelle, Université Pierre et Marie Curie, IRD 206, Paris, France
| | - Géraldine Caumes
- Centre National de la Recherche Scientifique, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Sorbonne Universités, UMR 7590, Muséum National d'Histoire Naturelle, Université Pierre et Marie Curie, IRD 206, Paris, France
| | - Gilles De Luca
- Laboratoire d'Écologie Microbienne de la Rhizosphère et Environnements Extrêmes, UMR 7265, Aix Marseille Univ, Centre National de la Recherche Scientifique, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Saint-Paul-lez-Durance, France
| | - Thierry Heulin
- Laboratoire d'Écologie Microbienne de la Rhizosphère et Environnements Extrêmes, UMR 7265, Aix Marseille Univ, Centre National de la Recherche Scientifique, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Saint-Paul-lez-Durance, France
| | - Elodie Duprat
- Centre National de la Recherche Scientifique, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Sorbonne Universités, UMR 7590, Muséum National d'Histoire Naturelle, Université Pierre et Marie Curie, IRD 206, Paris, France
| |
Collapse
|
23
|
Park DM, Overton KW, Liou MJ, Jiao Y. Identification of a U/Zn/Cu responsive global regulatory two-component system in Caulobacter crescentus. Mol Microbiol 2017; 104:46-64. [PMID: 28035693 DOI: 10.1111/mmi.13615] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/23/2016] [Indexed: 01/18/2023]
Abstract
Despite the well-known toxicity of uranium (U) to bacteria, little is known about how cells sense and respond to U. The recent finding of a U-specific stress response in Caulobacter crescentus has provided a foundation for studying the mechanisms of U- perception in bacteria. To gain insight into this process, we used a forward genetic screen to identify the regulatory components governing expression of the urcA promoter (PurcA ) that is strongly induced by U. This approach unearthed a previously uncharacterized two-component system, named UzcRS, which is responsible for U-dependent activation of PurcA . UzcRS is also highly responsive to zinc and copper, revealing a broader specificity than previously thought. Using ChIP-seq, we found that UzcR binds extensively throughout the genome in a metal-dependent manner and recognizes a noncanonical DNA-binding site. Coupling the genome-wide occupancy data with RNA-seq analysis revealed that UzcR is a global regulator of transcription, predominately activating genes encoding proteins that are localized to the cell envelope; these include metallopeptidases, multidrug-resistant efflux (MDR) pumps, TonB-dependent receptors and many proteins of unknown function. Collectively, our data suggest that UzcRS couples the perception of U, Zn and Cu with a novel extracytoplasmic stress response.
Collapse
Affiliation(s)
- Dan M Park
- Biosciences and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA, USA
| | - K Wesley Overton
- Biosciences and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA, USA
| | - Megan J Liou
- Biosciences and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA, USA
| | - Yongqin Jiao
- Biosciences and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA, USA
| |
Collapse
|
24
|
Wufuer R, Wei Y, Lin Q, Wang H, Song W, Liu W, Zhang D, Pan X, Gadd GM. Uranium Bioreduction and Biomineralization. ADVANCES IN APPLIED MICROBIOLOGY 2017; 101:137-168. [PMID: 29050665 DOI: 10.1016/bs.aambs.2017.01.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Following the development of nuclear science and technology, uranium contamination has been an ever increasing concern worldwide because of its potential for migration from the waste repositories and long-term contaminated environments. Physical and chemical techniques for uranium pollution are expensive and challenging. An alternative to these technologies is microbially mediated uranium bioremediation in contaminated water and soil environments due to its reduced cost and environmental friendliness. To date, four basic mechanisms of uranium bioremediation-uranium bioreduction, biosorption, biomineralization, and bioaccumulation-have been established, of which uranium bioreduction and biomineralization have been studied extensively. The objective of this review is to provide an understanding of recent developments in these two fields in relation to relevant microorganisms, mechanisms, influential factors, and obstacles.
Collapse
|
25
|
Majumder ELW, Wall JD. Uranium Bio-Transformations: Chemical or Biological Processes? ACTA ACUST UNITED AC 2017. [DOI: 10.4236/ojic.2017.72003] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
26
|
Two Outer Membrane Proteins Contribute to Caulobacter crescentus Cellular Fitness by Preventing Intracellular S-Layer Protein Accumulation. Appl Environ Microbiol 2016; 82:6961-6972. [PMID: 27663028 DOI: 10.1128/aem.02479-16] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Accepted: 09/16/2016] [Indexed: 01/18/2023] Open
Abstract
Surface layers, or S-layers, are two-dimensional protein arrays that form the outermost layer of many bacteria and archaea. They serve several functions, including physical protection of the cell from environmental threats. The high abundance of S-layer proteins necessitates a highly efficient export mechanism to transport the S-layer protein from the cytoplasm to the cell exterior. Caulobacter crescentus is unique in that it has two homologous, seemingly redundant outer membrane proteins, RsaFa and RsaFb, which together with other components form a type I protein translocation pathway for S-layer export. These proteins have homology to Escherichia coli TolC, the outer membrane channel of multidrug efflux pumps. Here we provide evidence that, unlike TolC, RsaFa and RsaFb are not involved in either the maintenance of membrane stability or the active export of antimicrobial compounds. Rather, RsaFa and RsaFb are required to prevent intracellular accumulation and aggregation of the S-layer protein RsaA; deletion of RsaFa and RsaFb led to a general growth defect and lowered cellular fitness. Using Western blotting, transmission electron microscopy, and transcriptome sequencing (RNA-seq), we show that loss of both RsaFa and RsaFb led to accumulation of insoluble RsaA in the cytoplasm, which in turn caused upregulation of a number of genes involved in protein misfolding and degradation pathways. These findings provide new insight into the requirement for RsaFa and RsaFb in cellular fitness and tolerance to antimicrobial agents and further our understanding of the S-layer export mechanism on both the transcriptional and translational levels in C. crescentusIMPORTANCE Decreased growth rate and reduced cell fitness are common side effects of protein production in overexpression systems. Inclusion bodies typically form inside the cell, largely due to a lack of sufficient export machinery to transport the overexpressed proteins to the extracellular environment. This phenomenon can conceivably also occur in natural systems. As one example of a system evolved to prevent intracellular protein accumulation, our study demonstrates that Caulobacter crescentus has two homologous outer membrane transporter proteins that are involved in S-layer export. This is an interesting case study that demonstrates how bacteria can evolve redundancy to ensure adequate protein export functionality and maintain high cellular fitness. Moreover, we provide evidence that these two outer membrane proteins, although being the closest C. crescentus homologs to TolC in E. coli, do not process TolC functionality in C. crescentus.
Collapse
|
27
|
Pierrefite-Carle V, Santucci-Darmanin S, Breuil V, Gritsaenko T, Vidaud C, Creff G, Solari PL, Pagnotta S, Al-Sahlanee R, Auwer CD, Carle GF. Effect of natural uranium on the UMR-106 osteoblastic cell line: impairment of the autophagic process as an underlying mechanism of uranium toxicity. Arch Toxicol 2016; 91:1903-1914. [DOI: 10.1007/s00204-016-1833-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 08/24/2016] [Indexed: 01/07/2023]
|
28
|
Boteva S, Radeva G, Traykov I, Kenarova A. Effects of long-term radionuclide and heavy metal contamination on the activity of microbial communities, inhabiting uranium mining impacted soils. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2016; 23:5644-5653. [PMID: 26578378 DOI: 10.1007/s11356-015-5788-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 11/09/2015] [Indexed: 06/05/2023]
Abstract
Ore mining and processing have greatly altered ecosystems, often limiting their capacity to provide ecosystem services critical to our survival. The soil environments of two abandoned uranium mines were chosen to analyze the effects of long-term uranium and heavy metal contamination on soil microbial communities using dehydrogenase and phosphatase activities as indicators of metal stress. The levels of soil contamination were low, ranging from 'precaution' to 'moderate', calculated as Nemerow index. Multivariate analyses of enzyme activities revealed the following: (i) spatial pattern of microbial endpoints where the more contaminated soils had higher dehydrogenase and phosphatase activities, (ii) biological grouping of soils depended on both the level of soil contamination and management practice, (iii) significant correlations between both dehydrogenase and alkaline phosphatase activities and soil organic matter and metals (Cd, Co, Cr, and Zn, but not U), and (iv) multiple relationships between the alkaline than the acid phosphatase and the environmental factors. The results showed an evidence of microbial tolerance and adaptation to the soil contamination established during the long-term metal exposure and the key role of soil organic matter in maintaining high microbial enzyme activities and mitigating the metal toxicity. Additionally, the results suggested that the soil microbial communities are able to reduce the metal stress by intensive phosphatase synthesis, benefiting a passive environmental remediation and provision of vital ecosystem services.
Collapse
Affiliation(s)
- Silvena Boteva
- Faculty of Biology, Sofia University "St. Kl. Ohridski", 8 Dragan Tsankov Blvd, Sofia, 1164, Bulgaria
| | - Galina Radeva
- Institute of Molecular Biology, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., bl. 21, Sofia, 1113, Bulgaria
| | - Ivan Traykov
- Faculty of Biology, Sofia University "St. Kl. Ohridski", 8 Dragan Tsankov Blvd, Sofia, 1164, Bulgaria
| | - Anelia Kenarova
- Faculty of Biology, Sofia University "St. Kl. Ohridski", 8 Dragan Tsankov Blvd, Sofia, 1164, Bulgaria.
| |
Collapse
|
29
|
Liang X, Csetenyi L, Gadd GM. Uranium bioprecipitation mediated by yeasts utilizing organic phosphorus substrates. Appl Microbiol Biotechnol 2016; 100:5141-51. [PMID: 26846744 DOI: 10.1007/s00253-016-7327-9] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Revised: 01/12/2016] [Accepted: 01/14/2016] [Indexed: 01/14/2023]
Abstract
In this research, we have demonstrated the ability of several yeast species to mediate U(VI) biomineralization through uranium phosphate biomineral formation when utilizing an organic source of phosphorus (glycerol 2-phosphate disodium salt hydrate (C3H7Na2O6P·xH2O (G2P)) or phytic acid sodium salt hydrate (C6H18O24P6·xNa(+)·yH2O (PyA))) in the presence of soluble UO2(NO3)2. The formation of meta-ankoleite (K2(UO2)2(PO4)2·6(H2O)), chernikovite ((H3O)2(UO2)2(PO4)2·6(H2O)), bassetite (Fe(++)(UO2)2(PO4)2·8(H2O)), and uramphite ((NH4)(UO2)(PO4)·3(H2O)) on cell surfaces was confirmed by X-ray diffraction in yeasts grown in a defined liquid medium amended with uranium and an organic phosphorus source, as well as in yeasts pre-grown in organic phosphorus-containing media and then subsequently exposed to UO2(NO3)2. The resulting minerals depended on the yeast species as well as physico-chemical conditions. The results obtained in this study demonstrate that phosphatase-mediated uranium biomineralization can occur in yeasts supplied with an organic phosphate substrate as sole source of phosphorus. Further understanding of yeast interactions with uranium may be relevant to development of potential treatment methods for uranium waste and utilization of organic phosphate sources and for prediction of microbial impacts on the fate of uranium in the environment.
Collapse
Affiliation(s)
- Xinjin Liang
- Geomicrobiology Group, School of Life Sciences, University of Dundee, Dundee, Scotland, DD1 5EH, UK
| | - Laszlo Csetenyi
- Concrete Technology Group, Department of Civil Engineering, University of Dundee, Dundee, Scotland, DD1 4HN, UK
| | - Geoffrey Michael Gadd
- Geomicrobiology Group, School of Life Sciences, University of Dundee, Dundee, Scotland, DD1 5EH, UK.
| |
Collapse
|
30
|
Pan X, Chen Z, Chen F, Cheng Y, Lin Z, Guan X. The mechanism of uranium transformation from U(VI) into nano-uramphite by two indigenous Bacillus thuringiensis strains. JOURNAL OF HAZARDOUS MATERIALS 2015; 297:313-319. [PMID: 26026850 DOI: 10.1016/j.jhazmat.2015.05.019] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Revised: 05/11/2015] [Accepted: 05/12/2015] [Indexed: 06/04/2023]
Abstract
The mechanism of uranium transformation from U(VI) into nano-uramphite by two indigenous Bacillus thuringiensis strains was investigated in the present work. Our data showed that the bacteria isolated from uranium mine possessed highly accumulation ability to U(VI), and the maximum accumulation capacity was around 400 mg U/g biomass (dry weight). X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR) analyzes indicated that the U(VI) was adsorbed on the bacterial surface firstly through coordinating with phosphate, CH2 and amide groups, and then needle-like amorphous uranium compounds were formed. With the extension of time, the extracellular crystalline substances were disappeared, but some particles were appeared in the intracellular region, and these particles were characterized as tetragonal-uramphite. Moreover, the disrupted experiment indicated that the cell-free extracts had better uranium-immobilization ability than cell debris. Our findings provided the understanding of the uranium transformation process from amorphous uranium to crystalline uramphite, which would be useful in the regulation of uranium immobilization process.
Collapse
Affiliation(s)
- Xiaohong Pan
- Key Lab of Biopesticide and Chemical Biology, Fujian Agriculture and Forestry University, Ministry of Education & Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Fuzhou, Fujian 350002, PR China; Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, PR China
| | - Zhi Chen
- Key Lab of Biopesticide and Chemical Biology, Fujian Agriculture and Forestry University, Ministry of Education & Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Fuzhou, Fujian 350002, PR China; Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, PR China
| | - Fanbing Chen
- Key Lab of Biopesticide and Chemical Biology, Fujian Agriculture and Forestry University, Ministry of Education & Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Fuzhou, Fujian 350002, PR China
| | - Yangjian Cheng
- Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, PR China
| | - Zhang Lin
- Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, PR China; School of Environment and Energy, South China University of Technology, Guangzhou 510006, PR China.
| | - Xiong Guan
- Key Lab of Biopesticide and Chemical Biology, Fujian Agriculture and Forestry University, Ministry of Education & Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Fuzhou, Fujian 350002, PR China.
| |
Collapse
|
31
|
Newsome L, Morris K, Trivedi D, Bewsher A, Lloyd JR. Biostimulation by Glycerol Phosphate to Precipitate Recalcitrant Uranium(IV) Phosphate. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2015; 49:11070-11078. [PMID: 26292021 DOI: 10.1021/acs.est.5b02042] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Stimulating the microbial reduction of aqueous uranium(VI) to insoluble U(IV) via electron donor addition has been proposed as a strategy to remediate uranium-contaminated groundwater in situ. However, concerns have been raised regarding the longevity of microbially precipitated U(IV) in the subsurface, particularly given that it may become remobilized if the conditions change to become oxidizing. An alternative mechanism is to stimulate the precipitation of poorly soluble uranium phosphates via the addition of an organophosphate and promote the development of reducing conditions. Here, we selected a sediment sample from a U.K. nuclear site and stimulated the microbial community with glycerol phosphate under anaerobic conditions to assess whether uranium phosphate precipitation was a viable bioremediation strategy. Results showed that U(VI) was rapidly removed from solution and precipitated as a reduced crystalline U(IV) phosphate mineral similar to ningyoite. This mineral was considerably more recalcitrant to oxidative remobilization than the products of microbial U(VI) reduction. Bacteria closely related to Pelosinus species may have played a key role in uranium removal in these experiments. This work has implications for the stewardship of uranium-contaminated groundwater, with the formation of U(IV) phosphates potentially offering a more effective strategy for maintaining low concentrations of uranium in groundwater over long time periods.
Collapse
Affiliation(s)
- Laura Newsome
- Williamson Research Centre and Research Centre for Radwaste Disposal, School of Earth, Atmospheric and Environmental Sciences, The University of Manchester , Williamson Building, Oxford Road, Manchester M13 9PL, U.K
| | - Katherine Morris
- Williamson Research Centre and Research Centre for Radwaste Disposal, School of Earth, Atmospheric and Environmental Sciences, The University of Manchester , Williamson Building, Oxford Road, Manchester M13 9PL, U.K
| | - Divyesh Trivedi
- National Nuclear Laboratory , Chadwick House, Birchwood, Warrington WA3 6AE, U.K
| | - Alastair Bewsher
- Williamson Research Centre and Research Centre for Radwaste Disposal, School of Earth, Atmospheric and Environmental Sciences, The University of Manchester , Williamson Building, Oxford Road, Manchester M13 9PL, U.K
| | - Jonathan R Lloyd
- Williamson Research Centre and Research Centre for Radwaste Disposal, School of Earth, Atmospheric and Environmental Sciences, The University of Manchester , Williamson Building, Oxford Road, Manchester M13 9PL, U.K
- National Nuclear Laboratory , Chadwick House, Birchwood, Warrington WA3 6AE, U.K
| |
Collapse
|
32
|
Miot J, Remusat L, Duprat E, Gonzalez A, Pont S, Poinsot M. Fe biomineralization mirrors individual metabolic activity in a nitrate-dependent Fe(II)-oxidizer. Front Microbiol 2015; 6:879. [PMID: 26441847 PMCID: PMC4562303 DOI: 10.3389/fmicb.2015.00879] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 08/10/2015] [Indexed: 12/15/2022] Open
Abstract
Microbial biomineralization sometimes leads to periplasmic encrustation, which is predicted to enhance microorganism preservation in the fossil record. Mineral precipitation within the periplasm is, however, thought to induce death, as a result of permeability loss preventing nutrient and waste transit across the cell wall. This hypothesis had, however, never been investigated down to the single cell level. Here, we cultured the nitrate reducing Fe(II) oxidizing bacteria Acidovorax sp. strain BoFeN1 that have been previously shown to promote the precipitation of a diversity of Fe minerals (lepidocrocite, goethite, Fe phosphate) encrusting the periplasm. We investigated the connection of Fe biomineralization with carbon assimilation at the single cell level, using a combination of electron microscopy and Nano-Secondary Ion Mass Spectrometry. Our analyses revealed strong individual heterogeneities of Fe biomineralization. Noteworthy, a small proportion of cells remaining free of any precipitate persisted even at advanced stages of biomineralization. Using pulse chase experiments with (13)C-acetate, we provide evidence of individual phenotypic heterogeneities of carbon assimilation, correlated with the level of Fe biomineralization. Whereas non- and moderately encrusted cells were able to assimilate acetate, higher levels of periplasmic encrustation prevented any carbon incorporation. Carbon assimilation only depended on the level of Fe encrustation and not on the nature of Fe minerals precipitated in the cell wall. Carbon assimilation decreased exponentially with increasing cell-associated Fe content. Persistence of a small proportion of non-mineralized and metabolically active cells might constitute a survival strategy in highly ferruginous environments. Eventually, our results suggest that periplasmic Fe biomineralization may provide a signature of individual metabolic status, which could be looked for in the fossil record and in modern environmental samples.
Collapse
Affiliation(s)
- Jennyfer Miot
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Muséum National d’Histoire Naturelle, Université Pierre et Marie Curie – Sorbonne Universités, CNRS UMR 7590, IRD 206Paris, France
| | - Laurent Remusat
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Muséum National d’Histoire Naturelle, Université Pierre et Marie Curie – Sorbonne Universités, CNRS UMR 7590, IRD 206Paris, France
| | - Elodie Duprat
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Muséum National d’Histoire Naturelle, Université Pierre et Marie Curie – Sorbonne Universités, CNRS UMR 7590, IRD 206Paris, France
| | - Adriana Gonzalez
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Muséum National d’Histoire Naturelle, Université Pierre et Marie Curie – Sorbonne Universités, CNRS UMR 7590, IRD 206Paris, France
| | - Sylvain Pont
- Département des Collections, Muséum National d’Histoire NaturelleParis, France
| | - Mélanie Poinsot
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Muséum National d’Histoire Naturelle, Université Pierre et Marie Curie – Sorbonne Universités, CNRS UMR 7590, IRD 206Paris, France
| |
Collapse
|
33
|
Transposon Mutagenesis Paired with Deep Sequencing of Caulobacter crescentus under Uranium Stress Reveals Genes Essential for Detoxification and Stress Tolerance. J Bacteriol 2015. [PMID: 26195598 DOI: 10.1128/jb.00382-15] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
UNLABELLED The ubiquitous aquatic bacterium Caulobacter crescentus is highly resistant to uranium (U) and facilitates U biomineralization and thus holds promise as an agent of U bioremediation. To gain an understanding of how C. crescentus tolerates U, we employed transposon (Tn) mutagenesis paired with deep sequencing (Tn-seq) in a global screen for genomic elements required for U resistance. Of the 3,879 annotated genes in the C. crescentus genome, 37 were found to be specifically associated with fitness under U stress, 15 of which were subsequently tested through mutational analysis. Systematic deletion analysis revealed that mutants lacking outer membrane transporters (rsaFa and rsaFb), a stress-responsive transcription factor (cztR), or a ppGpp synthetase/hydrolase (spoT) exhibited a significantly lower survival rate under U stress. RsaFa and RsaFb, which are homologues of TolC in Escherichia coli, have previously been shown to mediate S-layer export. Transcriptional analysis revealed upregulation of rsaFa and rsaFb by 4- and 10-fold, respectively, in the presence of U. We additionally show that rsaFa mutants accumulated higher levels of U than the wild type, with no significant increase in oxidative stress levels. Our results suggest a function for RsaFa and RsaFb in U efflux and/or maintenance of membrane integrity during U stress. In addition, we present data implicating CztR and SpoT in resistance to U stress. Together, our findings reveal novel gene targets that are key to understanding the molecular mechanisms of U resistance in C. crescentus. IMPORTANCE Caulobacter crescentus is an aerobic bacterium that is highly resistant to uranium (U) and has great potential to be used in U bioremediation, but its mechanisms of U resistance are poorly understood. We conducted a Tn-seq screen to identify genes specifically required for U resistance in C. crescentus. The genes that we identified have previously remained elusive using other omics approaches and thus provide significant insight into the mechanisms of U resistance by C. crescentus. In particular, we show that outer membrane transporters RsaFa and RsaFb, previously known as part of the S-layer export machinery, may confer U resistance by U efflux and/or by maintaining membrane integrity during U stress.
Collapse
|
34
|
Modulation of medium pH by Caulobacter crescentus facilitates recovery from uranium-induced growth arrest. Appl Environ Microbiol 2014; 80:5680-8. [PMID: 25002429 DOI: 10.1128/aem.01294-14] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The oxidized form of uranium [U(VI)] predominates in oxic environments and poses a major threat to ecosystems. Due to its ability to mineralize U(VI), the oligotroph Caulobacter crescentus is an attractive candidate for U(VI) bioremediation. However, the physiological basis for U(VI) tolerance is unclear. Here we demonstrated that U(VI) caused a temporary growth arrest in C. crescentus and three other bacterial species, although the duration of growth arrest was significantly shorter for C. crescentus. During the majority of the growth arrest period, cell morphology was unaltered and DNA replication initiation was inhibited. However, during the transition from growth arrest to exponential phase, cells with shorter stalks were observed, suggesting a decoupling between stalk development and the cell cycle. Upon recovery from growth arrest, C. crescentus proliferated with a growth rate comparable to that of a control without U(VI), although a fraction of these cells appeared filamentous with multiple replication start sites. Normal cell morphology was restored by the end of exponential phase. Cells did not accumulate U(VI) resistance mutations during the prolonged growth arrest, but rather, a reduction in U(VI) toxicity occurred concomitantly with an increase in medium pH. Together, these data suggest that C. crescentus recovers from U(VI)-induced growth arrest by reducing U(VI) toxicity through pH modulation. Our finding represents a unique U(VI) detoxification strategy and provides insight into how microbes cope with U(VI) under nongrowing conditions, a metabolic state that is prevalent in natural environments.
Collapse
|