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Khan Z, Elahi A, Bukhari DA, Rehman A. Cadmium sources, toxicity, resistance and removal by microorganisms-A potential strategy for cadmium eradication. JOURNAL OF SAUDI CHEMICAL SOCIETY 2022. [DOI: 10.1016/j.jscs.2022.101569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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2
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Rola A, Potok P, Wieczorek R, Mos M, Gumienna-Kontecka E, Potocki S. Coordination Properties of the Zinc Domains of BigR4 and SmtB Proteins in Nickel Systems─Designation of Key Donors. Inorg Chem 2022; 61:9454-9468. [PMID: 35696675 PMCID: PMC9241078 DOI: 10.1021/acs.inorgchem.2c00319] [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] [Indexed: 12/02/2022]
Abstract
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The increasing number
of antibiotic-resistant pathogens has become
one of the foremost health problems of modern times. One of the most
lethal and multidrug-resistant bacteria is Mycobacterium
tuberculosis (Mtb), which causes tuberculosis (TB).
TB continues to engulf health systems due to the significant development
of bacterial multidrug-resistant strains. Mammalian immune system
response to mycobacterial infection includes, but is not limited to,
increasing the concentration of zinc(II) and other divalent metal
ions in phagosome vesicles up to toxic levels. Metal ions are necessary
for the survival and virulence of bacteria but can be highly toxic
to organisms if their concentrations are not strictly controlled.
Therefore, understanding the mechanisms of how bacteria use metal
ions to maintain their optimum concentrations and survive under lethal
environmental conditions is essential. The mycobacterial SmtB protein,
one of the metal-dependent transcription regulators of the ArsR/SmtB
family, dissociates from DNA in the presence of high concentrations
of metals, activating the expression of metal efflux proteins. In
this work, we explore the properties of α5 metal-binding domains
of SmtB/BigR4 proteins (the latter being the SmtB homolog from nonpathogenic Mycobacterium smegmatis), and two mutants of BigR4
as ligands for nickel(II) ions. The study focuses on the specificity
of metal–ligand interactions and describes the effect of mutations
on the coordination properties of the studied systems. The results
of this research reveal that the Ni(II)-BigR4 α5 species are
more stable than the Ni(II)-SmtB α5 complexes. His mutations,
exchanging one of the histidines for alanine, cause a decrease in
the stability of Ni(II) complexes. Surprisingly, the lack of His102
resulted also in increased involvement of acidic amino acids in the
coordination. The results of this study may help to understand the
role of critical mycobacterial virulence factor—SmtB in metal
homeostasis. Although SmtB prefers Zn(II) binding, it may also bind
metal ions that prefer other coordination modes, for example, Ni(II).
We characterized the properties of such complexes in order to understand
the nature of mycobacterial SmtB when acting as a ligand for metal
ions, given that nickel and zinc ArsR family proteins possess analogous
metal-binding motifs. This may provide an introduction to the design
of a new antimicrobial strategy against the pathogenic bacterium M. tuberculosis. The
histidine-rich α5 domains of SmtB (L4, Mycobacterium
tuberculosis) and BigR4 (L1, Mycobacterium
smegmatis) were studied as ligands
for Ni(II). Point mutation analysis of L1 revealed that His102 and
106 preferably bind metal ions. The general Ni(II)-binding motif for
both of the ligands was established as HX3HX3DX3HX2ED. L1 forms more
stable complexes than L4 due to the stabilizing effect of arginine
residues.
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Affiliation(s)
- Anna Rola
- Faculty of Chemistry, University of Wroclaw, 14 Joliot-Curie Street, Wroclaw 50-383, Poland
| | - Paulina Potok
- Faculty of Chemistry, University of Wroclaw, 14 Joliot-Curie Street, Wroclaw 50-383, Poland
| | - Robert Wieczorek
- Faculty of Chemistry, University of Wroclaw, 14 Joliot-Curie Street, Wroclaw 50-383, Poland
| | - Magdalena Mos
- WMG, International Manufacturing Centre, University of Warwick, Coventry CV4 7AL, U.K
| | | | - Sławomir Potocki
- Faculty of Chemistry, University of Wroclaw, 14 Joliot-Curie Street, Wroclaw 50-383, Poland
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Divya TV, Acharya C. AzuR From the SmtB/ArsR Family of Transcriptional Repressors Regulates Metallothionein in Anabaena sp. Strain PCC 7120. Front Microbiol 2022; 12:782363. [PMID: 35095796 PMCID: PMC8790569 DOI: 10.3389/fmicb.2021.782363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Accepted: 11/30/2021] [Indexed: 11/19/2022] Open
Abstract
Metallothioneins (MTs) are cysteine-rich, metal-sequestering cytosolic proteins that play a key role in maintaining metal homeostasis and detoxification. We had previously characterized NmtA, a MT from the heterocystous, nitrogen-fixing cyanobacterium Anabaena sp. strain PCC 7120 and demonstrated its role in providing protection against cadmium toxicity. In this study, we illustrate the regulation of Anabaena NmtA by AzuR (Alr0831) belonging to the SmtB/ArsR family of transcriptional repressors. There is currently no experimental evidence for any functional role of AzuR. It is observed that azuR is located within the znuABC operon but in the opposite orientation and remotely away from the nmtA locus. Sequence analysis of AzuR revealed a high degree of sequence identity with Synechococcus SmtB and a distinct α5 metal binding site similar to that of SmtB. In order to characterize AzuR, we overexpressed it in Escherichia coli and purified it by chitin affinity chromatography. Far-UV circular dichroism spectroscopy indicated that the recombinant AzuR protein possessed a properly folded structure. Glutaraldehyde cross-linking and size-exclusion chromatography revealed that AzuR exists as a dimer of ∼28 kDa in solution. Analysis of its putative promoter region [100 bp upstream of nmtA open reading frame (ORF)] identified the presence of a 12–2–12 imperfect inverted repeat as the cis-acting element important for repressor binding. Electrophoretic mobility shift assays (EMSAs) showed concentration-dependent binding of recombinant dimeric AzuR with the promoter indicating that NmtA is indeed a regulatory target of AzuR. Binding of AzuR to DNA was disrupted in the presence of metal ions like Zn2+, Cd2+, Cu2+, Co2+, Ni2+, Pb2+, and Mn2+. The metal-dependent dissociation of protein–DNA complexes suggested the negative regulation of metal-inducible nmtA expression by AzuR. Overexpression of azuR in its native strain Anabaena 7120 enhanced the susceptibility to cadmium stress significantly. Overall, we propose a negative regulation of Anabaena MT by an α5 SmtB/ArsR metalloregulator AzuR.
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Affiliation(s)
- T V Divya
- Molecular Biology Division, Bhabha Atomic Research Centre, Mumbai, India.,Homi Bhabha National Institute, Mumbai, India
| | - Celin Acharya
- Molecular Biology Division, Bhabha Atomic Research Centre, Mumbai, India.,Homi Bhabha National Institute, Mumbai, India
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4
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Viswanathan T, Chen J, Wu M, An L, Kandavelu P, Sankaran B, Radhakrishnan M, Li M, Rosen BP. Functional and structural characterization of AntR, an Sb(III) responsive transcriptional repressor. Mol Microbiol 2021; 116:427-437. [PMID: 33786926 DOI: 10.1111/mmi.14721] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 03/21/2021] [Accepted: 03/25/2021] [Indexed: 12/01/2022]
Abstract
The ant operon of the antimony-mining bacterium Comamonas testosterone JL40 confers resistance to Sb(III). The operon is transcriptionally regulated by the product of the first gene in the operon, antR. AntR is a member of ArsR/SmtB family of metal/metalloid-responsive repressors resistance. We purified and characterized C. testosterone AntR and demonstrated that it responds to metalloids in the order Sb(III) = methylarsenite (MAs(III) >> As(III)). The protein was crystallized, and the structure was solved at 2.1 Å resolution. The homodimeric structure of AntR adopts a classical ArsR/SmtB topology architecture. The protein has five cysteine residues, of which Cys103a from one monomer and Cys113b from the other monomer, are proposed to form one Sb(III) binding site, and Cys113a and Cys103b forming a second binding site. This is the first report of the structure and binding properties of a transcriptional repressor with high selectivity for environmental antimony.
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Affiliation(s)
- Thiruselvam Viswanathan
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA
| | - Jian Chen
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA
| | - Minghan Wu
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, P.R. China
| | - Lijin An
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, P.R. China
| | - Palani Kandavelu
- SER-CAT and the Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, USA
| | - Banumathi Sankaran
- Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley Laboratory, Berkeley Center for Structural Biology, Berkeley, CA, USA
| | - Manohar Radhakrishnan
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA
| | - Mingshun Li
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, P.R. China
| | - Barry P Rosen
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA
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5
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Mitra A, Chatterjee S, Kataki S, Rastogi RP, Gupta DK. Bacterial tolerance strategies against lead toxicity and their relevance in bioremediation application. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2021; 28:14271-14284. [PMID: 33528774 DOI: 10.1007/s11356-021-12583-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Accepted: 01/18/2021] [Indexed: 06/12/2023]
Abstract
Among heavy metals, lead (Pb) is a non-essential metal having a higher toxicity and without any crucial known biological functions. Being widespread, non-biodegradable and persistent in every sphere of soil, air and water, Pb is responsible for severe health and environmental issues, which need appropriate remediation measures. However, microbes inhabiting Pb-contaminated area are found to have evolved distinctive mechanisms to successfully thrive in the Pb-contaminated environment without exhibiting any negative effects on their growth and metabolism. The defensive strategies used by bacteria to ameliorate the toxic effects of lead comprise biosorption, efflux, production of metal chelators like siderophores and metallothioneins and synthesis of exopolysaccharides, extracellular sequestration and intracellular bioaccumulation. Lead remediation technologies by employing microbes may appear as potential advantageous alternatives to the conventional physical and chemical means due to specificity, suitability for applying in situ condition and feasibility to upgrade by genetic engineering. Developing strategies by designing transgenic bacterial strain having specific metal binding properties and metal chelating proteins or higher metal adsorption ability and using bacterial activity such as incorporating plant growth-promoting rhizobacteria for improved Pb resistance, exopolysaccharide and siderophores and metallothionein-mediated immobilization may prove highly effective for formulating bioremediation vis-a-vis phytoremediation strategies.
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Affiliation(s)
- Anindita Mitra
- Bankura Christian College, Bankura, West Bengal, 722101, India
| | - Soumya Chatterjee
- Defence Research Laboratory, DRDO, Post Bag No. 02, Tezpur, Assam, 784001, India
| | - Sampriti Kataki
- Defence Research Laboratory, DRDO, Post Bag No. 02, Tezpur, Assam, 784001, India
| | - Rajesh P Rastogi
- Ministry of Environment, Forest and Climate Change, Indira Paryavaran Bhawan, Aliganj, Jorbagh Road, New Delhi, 110003, India
| | - Dharmendra K Gupta
- Ministry of Environment, Forest and Climate Change, Indira Paryavaran Bhawan, Aliganj, Jorbagh Road, New Delhi, 110003, India.
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Habjanič J, Mathew A, Eberl L, Freisinger E. Deciphering the Enigmatic Function of Pseudomonas Metallothioneins. Front Microbiol 2020; 11:1709. [PMID: 32793167 PMCID: PMC7387436 DOI: 10.3389/fmicb.2020.01709] [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: 05/11/2020] [Accepted: 06/29/2020] [Indexed: 11/20/2022] Open
Abstract
Metallothioneins (MTs) are low molecular weight, Cys-rich proteins that sequester both essential and non-essential metal ions. Despite being highly conserved in the Pseudomonas genus of Gram-negative bacteria, knowledge of their physiological function in this species is scarce. Using the strain P. fluorescens Q2-87 as a model organism, we investigated the role of a conserved MT in zinc homeostasis, cadmium detoxification as well as its implications in stress response. We show that MT expression is only induced in the stationary phase and provides a fitness benefit for long-term starvation survival, while it is not required for metal resistance and acquisition, oxidative or nitrosative stress response, biofilm formation or motility.
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Affiliation(s)
- Jelena Habjanič
- Department of Chemistry, University of Zurich, Zurich, Switzerland
| | - Anugraha Mathew
- Department of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
| | - Leo Eberl
- Department of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
| | - Eva Freisinger
- Department of Chemistry, University of Zurich, Zurich, Switzerland
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7
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Role of Microorganisms in the Remediation of Wastewater in Floating Treatment Wetlands: A Review. SUSTAINABILITY 2020. [DOI: 10.3390/su12145559] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
This article provides useful information for understanding the specific role of microbes in the pollutant removal process in floating treatment wetlands (FTWs). The current literature is collected and organized to provide an insight into the specific role of microbes toward plants and pollutants. Several aspects are discussed, such as important components of FTWs, common bacterial species, rhizospheric and endophytes bacteria, and their specific role in the pollutant removal process. The roots of plants release oxygen and exudates, which act as a substrate for microbial growth. The bacteria attach themselves to the roots and form biofilms to get nutrients from the plants. Along the plants, the microbial community also influences the performance of FTWs. The bacterial community contributes to the removal of nitrogen, phosphorus, toxic metals, hydrocarbon, and organic compounds. Plant–microbe interaction breaks down complex compounds into simple nutrients, mobilizes metal ions, and increases the uptake of pollutants by plants. The inoculation of the roots of plants with acclimatized microbes may improve the phytoremediation potential of FTWs. The bacteria also encourage plant growth and the bioavailability of toxic pollutants and can alleviate metal toxicity.
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8
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Vicente A, Sohm B, Flayac J, Rousselle P, Bauda P, Pagnout C. Toxicity mechanisms of ZnO UV-filters used in sunscreens toward the model cyanobacteria Synechococcus elongatus PCC 7942. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2019; 26:22450-22463. [PMID: 31161548 DOI: 10.1007/s11356-019-05057-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Accepted: 04/01/2019] [Indexed: 06/09/2023]
Abstract
Zinc oxide (ZnO) nanoparticles are commonly used in sunscreens for their UV-filtering properties. Their growing use can lead to their release into ecosystems, raising question about their toxicity. Effects of these engineered nanomaterials (ENMs) on cyanobacteria, which are important primary producers involved in many biogeochemical cycles, are unknown. In this study, we investigated by several complementary approaches the toxicological effects of two marketed ZnO-ENMs (coated and uncoated) on the model cyanobacteria Synechococcus elongatus PCC 7942. It was shown that despite the rapid adsorption of ENMs on cell surface, toxicity is mainly due to labile Zn released by ENMs. Zn dissipates cell membrane potential necessary for both photosynthesis and respiration, and induces oxidative stress leading to lipid peroxidation and DNA damages. It leads to global downregulation of photosystems, oxidative phosphorylation, and transcription/translation machineries. This also translates into significant decrease of intracellular ATP content and cell growth inhibition. However, there is no major loss of pigments and even rather an increase in exposed cells compared to controls. A proposed way to reduce the environmental impact of Zn would be the improvement of the coating stability to prevent solubility of ZnO-ENMs.
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Affiliation(s)
- Anne Vicente
- Laboratoire Interdisciplinaire des Environnements Continentaux (LIEC), UMR CNRS 7360, Université de Lorraine, Campus Bridoux, Rue du Général Delestraint, 57070, Metz, France
| | - Bénédicte Sohm
- Laboratoire Interdisciplinaire des Environnements Continentaux (LIEC), UMR CNRS 7360, Université de Lorraine, Campus Bridoux, Rue du Général Delestraint, 57070, Metz, France
| | - Justine Flayac
- CNRS, LIEC, UMR7360, Campus Bridoux, 57070, Metz, France
| | - Philippe Rousselle
- Laboratoire Interdisciplinaire des Environnements Continentaux (LIEC), UMR CNRS 7360, Université de Lorraine, Campus Bridoux, Rue du Général Delestraint, 57070, Metz, France
| | - Pascale Bauda
- Laboratoire Interdisciplinaire des Environnements Continentaux (LIEC), UMR CNRS 7360, Université de Lorraine, Campus Bridoux, Rue du Général Delestraint, 57070, Metz, France
- CNRS, LIEC, UMR7360, Campus Bridoux, 57070, Metz, France
| | - Christophe Pagnout
- Laboratoire Interdisciplinaire des Environnements Continentaux (LIEC), UMR CNRS 7360, Université de Lorraine, Campus Bridoux, Rue du Général Delestraint, 57070, Metz, France.
- CNRS, LIEC, UMR7360, Campus Bridoux, 57070, Metz, France.
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Nanda M, Kumar V, Sharma DK. Multimetal tolerance mechanisms in bacteria: The resistance strategies acquired by bacteria that can be exploited to 'clean-up' heavy metal contaminants from water. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2019; 212:1-10. [PMID: 31022608 DOI: 10.1016/j.aquatox.2019.04.011] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Revised: 04/10/2019] [Accepted: 04/15/2019] [Indexed: 05/27/2023]
Abstract
Heavy metal pollution is one of the major environmental concerns worldwide. Toxic heavy metals when untreated get accumulated in environment and can pose severe threats to living organisms. It is well known that metals play a major role either directly or indirectly in different metabolic processes of bacteria. This allows bacterial cells to grow even in the presence of some toxic heavy metals. Microbial biotechnology has thus emerged as an effective and eco friendly solution in recent years for bioremediation of heavy metals. Therefore, this review is focused on summarising bacterial adaptation mechanisms for various heavy metals. It also shares some applications of have metal tolerant bacteria in bioremediation. Bacteria have evolved a number of processes for heavy metal tolerance viz., transportation across cell membrane, accumulation on cell wall, intra as well as extracellular entrapment, formation of complexes and redox reactions which form the basis of different bioremediation strategies. The genetic determinants for most of these resistances are located on plasmids however some may be chromosomal as well. Bacterial cells can uptake heavy by both ATP dependent and ATP independent processes. Bacterial cell wall also plays a very important role in accumulating heavy metals by bacterial cells. Gram-positive bacteria accumulate much higher concentrations of heavy metals on their cell walls than that of metals gram -ve bacteria. The role of bacterial metallothioneins (MTs) in heavy metal has also been reported. Thus, heavy metal tolerant bacteria are important for bioremediation of heavy metal pollutants from areas containing high concentrations of particular heavy metals.
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Affiliation(s)
- Manisha Nanda
- Department of Biotechnology, Dolphin (PG) Institute of Biomedical and Natural Sciences, Dehradun, 248007, India.
| | - Vinod Kumar
- Department of Chemistry, Uttaranchal University, Dehradun, 248007, India.
| | - D K Sharma
- Department of Zoology and Biotechnology, H.N.B. Garhwal Central University, SRT Campus, Badshahi Thaul, Tehri, Uttarakhand, India
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10
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Interaction of Copper Toxicity and Oxidative Stress in Campylobacter jejuni. J Bacteriol 2018; 200:JB.00208-18. [PMID: 30150230 DOI: 10.1128/jb.00208-18] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Accepted: 08/16/2018] [Indexed: 11/20/2022] Open
Abstract
Copper is both a required micronutrient and a source of toxicity in most organisms, including Campylobacter jejuni Two proteins expressed in C. jejuni (termed CopA and CueO) have been shown to be a copper transporter and multicopper oxidase, respectively. We have isolated strains with mutations in these genes, and here we report that they were more susceptible to both the addition of copper in the growth media and to induced oxidative stress. Both mutant strains were defective in colonization of an avian host, and copper in the feed exacerbated the colonization deficiency. Overexpression of a cytoplasmic peptide derived from the normally periplasmic copper-binding region of CueO also caused copper intolerance compared to nonexpressing strains or strains expressing the non-copper-binding versions of the peptide. Taken together, the results indicate that copper toxicity in C. jejuni is due to a failure to effectively sequester cytoplasmic copper, resulting in an increase in copper-mediated oxidative damage.IMPORTANCE Copper is a required micronutrient for most aerobic organisms, but it is universally toxic at elevated levels. These organisms use homeostatic mechanisms that allow for cells to acquire enough of the element to sustain metabolic requirements while ensuring that lethal levels cannot build up in the cell. Campylobacter jejuni is an important foodborne pathogen that typically makes its way into the food chain through contaminated poultry. C. jejuni has a metabolic requirement for copper and encodes a copper detoxification system. In the course of studying this system, we have learned that it is important for avian colonization. We have also gained insight into how copper exerts its toxic effects in C. jejuni by promoting oxidative stress.
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Roy R, Samanta S, Patra S, Mahato NK, Saha RP. In silico identification and characterization of sensory motifs in the transcriptional regulators of the ArsR-SmtB family. Metallomics 2018; 10:1476-1500. [PMID: 30191942 DOI: 10.1039/c8mt00082d] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The ArsR-SmtB family of proteins displays the greatest diversity among the bacterial metal-binding transcriptional regulators with regard to the variety of metal ions that they can sense. In the presence of increased levels of toxic heavy metals, these proteins dissociate from their cognate DNA upon the direct binding of metal ions to the appropriate sites, designated motifs on the proteins, either at the interface of the dimers or at the intra-subunit locations. In addition to the metal-mediated regulation, some proteins were also found to control transcription via redox reactions. In the present work, we have identified several new sequence motifs and expanded the knowledge base of metal binding sites in the ArsR-SmtB family of transcriptional repressors, and characterized them in terms of the ligands to the metal, distribution among different phyla of bacteria and archaea, amino acid propensities, protein length distributions and evolutionary interrelationships. We built structural models of the motifs to show the importance of specific residues in an individual motif. The wide abundance of these motifs in sequences of bacteria and archaea indicates the importance of these regulators in combating metal-toxicity within and outside of the hosts. We also show that by using residue composition, one can distinguish the ArsR-SmtB proteins from other metalloregulatory families. In addition, we show the importance of horizontal gene transfer in microorganisms, residing in similar habitats, on the evolution of the structural motifs in the family. Knowledge of the diverse metalloregulatory systems in microorganisms could enable us to manipulate specific genes that may result in a toxic metal-free environment.
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Affiliation(s)
- Rima Roy
- Department of Biotechnology, School of Biotechnology, Adamas University, Kolkata 700 126, India.
| | - Saikat Samanta
- Department of Biotechnology, School of Biotechnology, Adamas University, Kolkata 700 126, India.
| | - Surajit Patra
- Department of Biotechnology, School of Biotechnology, Adamas University, Kolkata 700 126, India.
| | - Nav Kumar Mahato
- Department of Mathematics, School of Science, Adamas University, Kolkata 700 126, India
| | - Rudra P Saha
- Department of Biotechnology, School of Biotechnology, Adamas University, Kolkata 700 126, India.
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13
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T V D, Chandwadkar P, Acharya C. NmtA, a novel metallothionein of Anabaena sp. strain PCC 7120 imparts protection against cadmium stress but not oxidative stress. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2018; 199:152-161. [PMID: 29626757 DOI: 10.1016/j.aquatox.2018.03.035] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Revised: 03/12/2018] [Accepted: 03/29/2018] [Indexed: 06/08/2023]
Abstract
Metallothioneins (MTs) are low molecular weight, sulfhydryl-containing, cysteine-rich, metal-binding proteins. Eukaryotes have multiple metallothionein genes; however, there is dearth of reports on prokaryotic metallothioneins. Bacterial MTs with SmtA from Synechococcus PCC 7942 as prototype have been studied in the context of cadmium detoxification. In this study, a smtA related ORF, namely nmtA, was identified in the heterocystous, nitrogen-fixing cyanobacterium, Anabaena PCC 7120. A recombinant N-terminal histidine-tagged Anabaena NmtA protein was overexpressed in Escherichia coli and purified. The protein was identified by peptide mass fingerprinting using MALDI-TOF Mass Spectrometry as putative metallothionein of Anabaena PCC 7120 with a calculated mass of ∼6.1 kDa. While the native metallated NmtA exhibited resistance against proteolysis, metal free apo-NmtA resulting from acid and dithiothreitol (DTT) treatment could be digested by proteinase K revealing a metal dependent proteolytic protection of NmtA. Expression of nmtA in Anabaena PCC 7120 was induced evidently by cadmium, zinc and copper but not by uranium or hydrogen peroxide. Recombinant Anabaena PCC 7120 overexpressing NmtA protein revealed superior cadmium tolerance but showed limited influence against oxidative stress tolerance as compared with the strain carrying vector alone. In contrast, a mutant of Synechococcus PCC 7942 deficient in MT locus was found to be highly susceptible to H2O2 indicating a likely involvement of cyanobacterial MT in protection against oxidative damage. Overall, the study improved our understanding of metal tolerance mechanisms in Anabaena PCC 7120 by demonstrating a key role of NmtA in cadmium tolerance.
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Affiliation(s)
- Divya T V
- Molecular Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai, 400085, India
| | - Pallavi Chandwadkar
- Molecular Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai, 400085, India
| | - Celin Acharya
- Molecular Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai, 400085, India; Homi Bhabha National Institute, Anushakti Nagar, Mumbai, 400094, India.
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14
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Lead absorption mechanisms in bacteria as strategies for lead bioremediation. Appl Microbiol Biotechnol 2018; 102:5437-5444. [PMID: 29736824 DOI: 10.1007/s00253-018-8969-6] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Revised: 03/23/2018] [Accepted: 03/24/2018] [Indexed: 02/04/2023]
Abstract
Bacteria exhibit a number of metabolism-dependent and metabolism-independent processes for the uptake and accumulation of toxic metals. The removal of these metals from environmental sources such as soil, sludge, and wastewaters using microbe-based technologies provide an alternative for their recovery and remediation. Lead (Pb) is a pervasive metal in the environment that adversely affects all living organisms. Many aspects of metal-microbe interactions remain unexploited in biotechnology and further development and application is necessary, particularly to the problem of Pb release into the environment. Thus, this review provides a synopsis of the most important bacterial phenotypes and biochemical attributes that are instrumental in lead bioremediation, along with what is known of their genetic background that can be exploited or improved through genetic engineering. This review also highlights the potential of Pb-resistant bacteria in bringing about detoxification of Pb-contaminated terrestrial and aquatic systems in a highly sustainable and environmental friendly manner, and the existing challenges that still lie in the path to in situ and large-scale bioremediation.
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15
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Rahman MT, Karim MM. Metallothionein: a Potential Link in the Regulation of Zinc in Nutritional Immunity. Biol Trace Elem Res 2018; 182:1-13. [PMID: 28585004 DOI: 10.1007/s12011-017-1061-8] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Accepted: 05/22/2017] [Indexed: 01/03/2023]
Abstract
Nutritional immunity describes mechanisms for withholding essential transition metals as well as directing the toxicity of these metals against infectious agents. Zinc is one of these transition elements that are essential for both humans and microbial pathogens. At the same time, Zn can be toxic both for man and microbes if its concentration is higher than the tolerance limit. Therefore a "delicate" balance of Zn must be maintained to keep the immune cells surveilling while making the level of Zn either to starve or to intoxicate the pathogens. On the other hand, the invading pathogens will exploit the host Zn pool for its survival and replication. Apparently, different sets of protein in human and bacteria are involved to maintain their Zn need. Metallothionein (MT)-a group of low molecular weight proteins, is well known for its Zn-binding ability and is expected to play an important role in that Zn balance at the time of active infection. However, the differences in structural, functional, and molecular control of biosynthesis between human and bacterial MT might play an important role to determine the proper use of Zn and the winning side. The current review explains the possible involvement of human and bacterial MT at the time of infection to control and exploit Zn for their need.
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16
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Habjanič J, Zerbe O, Freisinger E. A histidine-rich Pseudomonas metallothionein with a disordered tail displays higher binding capacity for cadmium than zinc. Metallomics 2018; 10:1415-1429. [DOI: 10.1039/c8mt00193f] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The NMR solution structure of a Pseudomonas metallothionein reveals a different binding capacity for ZnII and CdII ions that results in two novel metal-cluster topologies. Replacement of a non-coordinating residue by histidine decreases the kinetic lability of the cluster. All three structures reported show an identical protein fold.
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Affiliation(s)
- Jelena Habjanič
- Department of Chemistry
- University of Zurich
- Zurich
- Switzerland
| | - Oliver Zerbe
- Department of Chemistry
- University of Zurich
- Zurich
- Switzerland
| | - Eva Freisinger
- Department of Chemistry
- University of Zurich
- Zurich
- Switzerland
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17
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Kushwaha A, Hans N, Kumar S, Rani R. A critical review on speciation, mobilization and toxicity of lead in soil-microbe-plant system and bioremediation strategies. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2018; 147:1035-1045. [PMID: 29976006 DOI: 10.1016/j.ecoenv.2017.09.049] [Citation(s) in RCA: 187] [Impact Index Per Article: 31.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Revised: 09/15/2017] [Accepted: 09/17/2017] [Indexed: 05/18/2023]
Abstract
Lead accumulation in soils is of serious concern in agricultural production due to the harmful effects on soil microflora, crop growth and food safety. In soil, speciation of lead greatly affects its bioavailability and thus its toxicity on plants and microbes. Many plants and bacteria have evolved to develop detoxification mechanisms to counter the toxic effect of lead. Factors influencing the lead speciation include soil pH, organic matter, presence of various amendments, clay minerals and presence of organic colloids and iron oxides. Unlike, other metals little is known about the speciation and mobility of lead in soil. This review focuses on the speciation of lead in soil, its mobility, toxicity, uptake and detoxification mechanisms in plants and bacteria and bioremediation strategies for remediation of lead contaminated repositories.
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Affiliation(s)
- Anamika Kushwaha
- Department of Biotechnology, Motilal Nehru National Institute of Technology, Teliyarganj, Allahabad, Uttar Pradesh, India
| | - Nidhi Hans
- Department of Biotechnology, Motilal Nehru National Institute of Technology, Teliyarganj, Allahabad, Uttar Pradesh, India
| | - Sanjay Kumar
- Department of Biotechnology, Motilal Nehru National Institute of Technology, Teliyarganj, Allahabad, Uttar Pradesh, India
| | - Radha Rani
- Department of Biotechnology, Motilal Nehru National Institute of Technology, Teliyarganj, Allahabad, Uttar Pradesh, India.
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18
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Osman D, Foster AW, Chen J, Svedaite K, Steed JW, Lurie-Luke E, Huggins TG, Robinson NJ. Fine control of metal concentrations is necessary for cells to discern zinc from cobalt. Nat Commun 2017; 8:1884. [PMID: 29192165 PMCID: PMC5709419 DOI: 10.1038/s41467-017-02085-z] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Accepted: 11/06/2017] [Indexed: 12/31/2022] Open
Abstract
Bacteria possess transcription factors whose DNA-binding activity is altered upon binding to specific metals, but metal binding is not specific in vitro. Here we show that tight regulation of buffered intracellular metal concentrations is a prerequisite for metal specificity of Zur, ZntR, RcnR and FrmR in Salmonella Typhimurium. In cells, at non-inhibitory elevated concentrations, Zur and ZntR, only respond to Zn(II), RcnR to cobalt and FrmR to formaldehyde. However, in vitro all these sensors bind non-cognate metals, which alters DNA binding. We model the responses of these sensors to intracellular-buffered concentrations of Co(II) and Zn(II) based upon determined abundances, metal affinities and DNA affinities of each apo- and metalated sensor. The cognate sensors are modelled to respond at the lowest concentrations of their cognate metal, explaining specificity. However, other sensors are modelled to respond at concentrations only slightly higher, and cobalt or Zn(II) shock triggers mal-responses that match these predictions. Thus, perfect metal specificity is fine-tuned to a narrow range of buffered intracellular metal concentrations.
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Affiliation(s)
- Deenah Osman
- Department of Biosciences, Durham University, Durham, DH1 3LE, UK.,Department of Chemistry, Durham University, Durham, DH1 3LE, UK
| | - Andrew W Foster
- Department of Biosciences, Durham University, Durham, DH1 3LE, UK.,Department of Chemistry, Durham University, Durham, DH1 3LE, UK
| | - Junjun Chen
- Procter and Gamble, Mason Business Center, Cincinnati, OH, 45040, USA
| | - Kotryna Svedaite
- Department of Biosciences, Durham University, Durham, DH1 3LE, UK.,Department of Chemistry, Durham University, Durham, DH1 3LE, UK
| | | | - Elena Lurie-Luke
- Procter and Gamble, Singapore Innovation Center, Singapore, 138589, Singapore
| | - Thomas G Huggins
- Procter and Gamble, Mason Business Center, Cincinnati, OH, 45040, USA
| | - Nigel J Robinson
- Department of Biosciences, Durham University, Durham, DH1 3LE, UK. .,Department of Chemistry, Durham University, Durham, DH1 3LE, UK.
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19
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Saha RP, Samanta S, Patra S, Sarkar D, Saha A, Singh MK. Metal homeostasis in bacteria: the role of ArsR-SmtB family of transcriptional repressors in combating varying metal concentrations in the environment. Biometals 2017; 30:459-503. [PMID: 28512703 DOI: 10.1007/s10534-017-0020-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2017] [Accepted: 05/09/2017] [Indexed: 02/02/2023]
Abstract
Bacterial infections cause severe medical problems worldwide, resulting in considerable death and loss of capital. With the ever-increasing rise of antibiotic-resistant bacteria and the lack of development of new antibiotics, research on metal-based antimicrobial therapy has now gained pace. Metal ions are essential for survival, but can be highly toxic to organisms if their concentrations are not strictly controlled. Through evolution, bacteria have acquired complex metal-management systems that allow them to acquire metals that they need for survival in different challenging environments while evading metal toxicity. Metalloproteins that controls these elaborate systems in the cell, and linked to key virulence factors, are promising targets for the anti-bacterial drug development. Among several metal-sensory transcriptional regulators, the ArsR-SmtB family displays greatest diversity with several distinct metal-binding and nonmetal-binding motifs that have been characterized. These prokaryotic metolloregulatory transcriptional repressors represses the expression of operons linked to stress-inducing concentrations of metal ions by directly binding to the regulatory regions of DNA, while derepression results from direct binding of metal ions by these homodimeric proteins. Many bacteria, e.g., Mycobacterium tuberculosis, Bacillus anthracis, etc., have evolved to acquire multiple metal-sensory motifs which clearly demonstrate the importance of regulating concentrations of multiple metal ions. Here, we discussed the mechanisms of how ArsR-SmtB family regulates the intracellular bioavailability of metal ions both inside and outside of the host. Knowledge of the metal-challenges faced by bacterial pathogens and their survival strategies will enable us to develop the next generation drugs.
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Affiliation(s)
- Rudra P Saha
- Department of Biotechnology, School of Biotechnology, Adamas University, Kolkata, 700126, India.
| | - Saikat Samanta
- Department of Microbiology, School of Science, Adamas University, Kolkata, 700126, India
| | - Surajit Patra
- Department of Biotechnology, School of Biotechnology, Adamas University, Kolkata, 700126, India
| | - Diganta Sarkar
- Department of Biotechnology, Techno India University, Kolkata, 700091, India
| | - Abinit Saha
- Department of Biotechnology, School of Biotechnology, Adamas University, Kolkata, 700126, India
| | - Manoj Kumar Singh
- Department of Biotechnology, School of Biotechnology, Adamas University, Kolkata, 700126, India
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20
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Dalecki AG, Crawford CL, Wolschendorf F. Copper and Antibiotics: Discovery, Modes of Action, and Opportunities for Medicinal Applications. Adv Microb Physiol 2017; 70:193-260. [PMID: 28528648 DOI: 10.1016/bs.ampbs.2017.01.007] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
Copper is a ubiquitous element in the environment as well as living organisms, with its redox capabilities and complexation potential making it indispensable for many cellular functions. However, these same properties can be highly detrimental to prokaryotes and eukaryotes when not properly controlled, damaging many biomolecules including DNA, lipids, and proteins. To restrict free copper concentrations, all bacteria have developed mechanisms of resistance, sequestering and effluxing labile copper to minimize its deleterious effects. This weakness is actively exploited by phagocytes, which utilize a copper burst to destroy pathogens. Though administration of free copper is an unreasonable therapeutic antimicrobial itself, due to insufficient selectivity between host and pathogen, small-molecule ligands may provide an opportunity for therapeutic mimicry of the immune system. By modulating cellular entry, complex stability, resistance evasion, and target selectivity, ligand/metal coordination complexes can synergistically result in high levels of antibacterial activity. Several established therapeutic drugs, such as disulfiram and pyrithione, display remarkable copper-dependent inhibitory activity. These findings have led to development of new drug discovery techniques, using copper ions as the focal point. High-throughput screens for copper-dependent inhibitors against Mycobacterium tuberculosis and Staphylococcus aureus uncovered several new compounds, including a new class of inhibitors, the NNSNs. In this review, we highlight the microbial biology of copper, its antibacterial activities, and mechanisms to discover new inhibitors that synergize with copper.
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Affiliation(s)
- Alex G Dalecki
- The University of Alabama at Birmingham, Birmingham, AL, United States
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21
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Zn2+-Inducible Expression Platform for Synechococcus sp. Strain PCC 7002 Based on the smtA Promoter/Operator and smtB Repressor. Appl Environ Microbiol 2017; 83:AEM.02491-16. [PMID: 27836841 DOI: 10.1128/aem.02491-16] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2016] [Accepted: 11/07/2016] [Indexed: 12/31/2022] Open
Abstract
Synechococcus sp. strain PCC 7002 has been gaining significance as both a model system for photosynthesis research and for industrial applications. Until recently, the genetic toolbox for this model cyanobacterium was rather limited and relied primarily on tools that only allowed constitutive gene expression. This work describes a two-plasmid, Zn2+-inducible expression platform that is coupled with a zurA mutation, providing enhanced Zn2+ uptake. The control elements are based on the metal homeostasis system of a class II metallothionein gene (smtA7942) and its cognate SmtB7942 repressor from Synechococcus elongatus strain PCC 7942. Under optimal induction conditions, yellow fluorescent protein (YFP) levels were about half of those obtained with the strong, constitutive phycocyanin (cpcBA6803) promoter of Synechocystis sp. strain PCC 6803. This metal-inducible expression system in Synechococcus sp. strain PCC 7002 allowed the titratable gene expression of YFP that was up to 19-fold greater than the background level. This system was utilized successfully to control the expression of the Drosophila melanogaster β-carotene 15,15'-dioxygenase, NinaB, which is toxic when constitutively expressed from a strong promoter in Synechococcus sp. strain PCC 7002. Together, these properties establish this metal-inducible system as an additional useful tool that is capable of controlling gene expression for applications ranging from basic research to synthetic biology in Synechococcus sp. strain PCC 7002. IMPORTANCE This is the first metal-responsive expression system in cyanobacteria, to our knowledge, that does not exhibit low sensitivity for induction, which is one of the major hurdles for utilizing this class of genetic tools. In addition, high levels of expression can be generated that approximate those of established constitutive systems, with the added advantage of titratable control. Together, these properties establish this Zn2+-inducible system, which is based on the smtA7942 operator/promoter and smtB7942 repressor, as a versatile gene expression platform that expands the genetic toolbox of Synechococcus sp. strain PCC 7002.
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22
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Khan Z, Rehman A, Hussain SZ, Nisar MA, Zulfiqar S, Shakoori AR. Cadmium resistance and uptake by bacterium, Salmonella enterica 43C, isolated from industrial effluent. AMB Express 2016; 6:54. [PMID: 27491862 PMCID: PMC4974214 DOI: 10.1186/s13568-016-0225-9] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Accepted: 07/26/2016] [Indexed: 11/10/2022] Open
Abstract
Cadmium resistant bacterium, isolated from industrial wastewater, was characterized as Salmonella enterica 43C on the basis of biochemical and 16S rRNA ribotyping. It is first ever reported S. enterica 43C bared extreme resistance against heavy metal consortia in order of Pb(2+)>Cd(2+)>As(3+)>Zn(2+)>Cr(6+)>Cu(2+)>Hg(2+). Cd(2+) stress altered growth pattern of the bacterium in time dependent manner. It could remove nearly 57 % Cd(2+) from the medium over a period of 8 days. Kinetic and thermodynamic studies based on various adsorption isotherm models (Langmuir and Freundlich) depicted the Cd(2+) biosorption as spontaneous, feasible and endothermic in nature. Interestingly, the bacterium followed pseudo first order kinetics, making it a good biosorbent for heavy metal ions. The S. enterica 43C Cd(2+) processivity was significantly influenced by temperature, pH, initial Cd(2+) concentration, biomass dosage and co-metal ions. FTIR analysis of the bacterium revealed the active participation of amide and carbonyl moieties in Cd(2+) adsorption confirmed by EDX analysis. Electron micrographs beckoned further surface adsorption and increased bacterial size due to intracellular Cd(2+) accumulation. An overwhelming increase in glutathione and other non-protein thiols levels played a significant role in thriving oxidative stress generated by metal cations. Presence of metallothionein clearly depicted the role of such proteins in bacterial metal resistance mechanism. The present study results clearly declare S. enterica 43C a suitable candidate for green chemistry to bioremediate environmental Cd(2+).
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Affiliation(s)
- Zaman Khan
- Department of Microbiology and Molecular Genetics, University of the Punjab, New Campus, Lahore, 54590 Pakistan
| | - Abdul Rehman
- Department of Microbiology and Molecular Genetics, University of the Punjab, New Campus, Lahore, 54590 Pakistan
| | - Syed Z. Hussain
- Department of Chemistry, SBA School of Science and Engineering (SBASSE), Lahore University of Management Sciences (LUMS), DHA, Lahore Cantt, 54792 Pakistan
| | - Muhammad A. Nisar
- Department of Microbiology, Govt. College University Faislabad, Faislabad, Pakistan
| | - Soumble Zulfiqar
- School of Biological Sciences, University of the Punjab, New Campus, Lahore, 54590 Pakistan
| | - Abdul R. Shakoori
- School of Biological Sciences, University of the Punjab, New Campus, Lahore, 54590 Pakistan
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23
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Giner-Lamia J, Pereira SB, Bovea-Marco M, Futschik ME, Tamagnini P, Oliveira P. Extracellular Proteins: Novel Key Components of Metal Resistance in Cyanobacteria? Front Microbiol 2016; 7:878. [PMID: 27375598 PMCID: PMC4894872 DOI: 10.3389/fmicb.2016.00878] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Accepted: 05/24/2016] [Indexed: 11/13/2022] Open
Abstract
Metals are essential for all living organisms and required for fundamental biochemical processes. However, when in excess, metals can turn into highly-toxic agents able to disrupt cell membranes, alter enzymatic activities, and damage DNA. Metal concentrations are therefore tightly controlled inside cells, particularly in cyanobacteria. Cyanobacteria are ecologically relevant prokaryotes that perform oxygenic photosynthesis and can be found in many different marine and freshwater ecosystems, including environments contaminated with heavy metals. As their photosynthetic machinery imposes high demands for metals, homeostasis of these micronutrients has been widely studied in cyanobacteria. So far, most studies have focused on how cells are capable of controlling their internal metal pools, with a strong bias toward the analysis of intracellular processes. Ultrastructure, modulation of physiology, dynamic changes in transcription and protein levels have been studied, but what takes place in the extracellular environment when cells are exposed to an unbalanced metal availability remains largely unknown. The interest in studying the subset of proteins present in the extracellular space has only recently begun and the identification and functional analysis of the cyanobacterial exoproteomes are just emerging. Remarkably, metal-related proteins such as the copper-chaperone CopM or the iron-binding protein FutA2 have already been identified outside the cell. With this perspective, we aim to raise the awareness that metal-resistance mechanisms are not yet fully known and hope to motivate future studies assessing the role of extracellular proteins on bacterial metal homeostasis, with a special focus on cyanobacteria.
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Affiliation(s)
- Joaquín Giner-Lamia
- Systems Biology and Bioinformatics Laboratory, Centro de Ciências do Mar, Universidade do AlgarveFaro, Portugal; Center for Biomedical Research, Universidade do AlgarveFaro, Portugal
| | - Sara B Pereira
- Instituto de Investigação e Inovação em Saúde, Universidade do PortoPorto, Portugal; Instituto de Biologia Molecular e Celular, Universidade do PortoPorto, Portugal
| | | | - Matthias E Futschik
- Systems Biology and Bioinformatics Laboratory, Centro de Ciências do Mar, Universidade do AlgarveFaro, Portugal; Center for Biomedical Research, Universidade do AlgarveFaro, Portugal
| | - Paula Tamagnini
- Instituto de Investigação e Inovação em Saúde, Universidade do PortoPorto, Portugal; Instituto de Biologia Molecular e Celular, Universidade do PortoPorto, Portugal; Faculdade de Ciências, Departamento de Biologia, Universidade do PortoPorto, Portugal
| | - Paulo Oliveira
- Instituto de Investigação e Inovação em Saúde, Universidade do PortoPorto, Portugal; Instituto de Biologia Molecular e Celular, Universidade do PortoPorto, Portugal
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24
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Acharya C, Blindauer CA. Unexpected Interactions of the Cyanobacterial Metallothionein SmtA with Uranium. Inorg Chem 2016; 55:1505-15. [DOI: 10.1021/acs.inorgchem.5b02327] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Celin Acharya
- Molecular
Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai, India
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25
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Determination of zinc, cadmium and lead bioavailability in contaminated soils at the single-cell level by a combination of whole-cell biosensors and flow cytometry. SENSORS 2015; 15:8981-99. [PMID: 25894939 PMCID: PMC4431249 DOI: 10.3390/s150408981] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Revised: 04/02/2015] [Accepted: 04/10/2015] [Indexed: 11/17/2022]
Abstract
Zinc, lead and cadmium are metallic trace elements (MTEs) that are widespread in the environment and tend to accumulate in soils because of their low mobility and non-degradability. The purpose of this work is to evaluate the applicability of biosensors as tools able to provide data about the bioavailability of such MTEs in contaminated soils. Here, we tested the genetically-engineered strain Escherichia coli pP(ZntA)gfp as a biosensor applicable to the detection of zinc, lead and cadmium by the biosynthesis of green fluorescent protein (GFP) accumulating inside the cells. Flow cytometry was used to investigate the fluorescence induced by the MTEs. A curvilinear response to zinc between 0 and 25 mg/L and another curvilinear response to cadmium between 0 and 1.5 mg/L were highlighted in liquid media, while lead did not produce exploitable results. The response relating to a Zn2+/Cd2+ ratio of 10 was further investigated. In these conditions, E. coli pP(ZntA)gfp responded to cadmium only. Several contaminated soils with a Zn2+/Cd2+ ratio of 10 were analyzed with the biosensor, and the metallic concentrations were also measured by atomic absorption spectroscopy. Our results showed that E. coli pP(ZntA)gfp could be used as a monitoring tool for contaminated soils being processed.
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26
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Martín-Betancor K, Rodea-Palomares I, Muñoz-Martín MA, Leganés F, Fernández-Piñas F. Construction of a self-luminescent cyanobacterial bioreporter that detects a broad range of bioavailable heavy metals in aquatic environments. Front Microbiol 2015; 6:186. [PMID: 25806029 PMCID: PMC4353254 DOI: 10.3389/fmicb.2015.00186] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Accepted: 02/19/2015] [Indexed: 11/13/2022] Open
Abstract
A self-luminescent bioreporter strain of the unicellular cyanobacterium Synechococcus sp. PCC 7942 was constructed by fusing the promoter region of the smt locus (encoding the transcriptional repressor SmtB and the metallothionein SmtA) to luxCDABE from Photorhabdus luminescens; the sensor smtB gene controlling the expression of smtA was cloned in the same vector. The bioreporter performance was tested with a range of heavy metals and was shown to respond linearly to divalent Zn, Cd, Cu, Co, Hg, and monovalent Ag. Chemical modeling was used to link bioreporter response with metal speciation and bioavailability. Limits of Detection (LODs), Maximum Permissive Concentrations (MPCs) and dynamic ranges for each metal were calculated in terms of free ion concentrations. The ranges of detection varied from 11 to 72 pM for Hg2+ (the ion to which the bioreporter was most sensitive) to 1.54–5.35 μM for Cd2+ with an order of decreasing sensitivity as follows: Hg2+ >> Cu2+ >> Ag+ > Co2+ ≥ Zn2+ > Cd2+. However, the maximum induction factor reached 75-fold in the case of Zn2+ and 56-fold in the case of Cd2+, implying that Zn2+ is the preferred metal in vivo for the SmtB sensor, followed by Cd2+, Ag+ and Cu2+ (around 45–50-fold induction), Hg2+ (30-fold) and finally Co2+ (20-fold). The bioreporter performance was tested in real environmental samples with different water matrix complexity artificially contaminated with increasing concentrations of Zn, Cd, Ag, and Cu, confirming its validity as a sensor of free heavy metal cations bioavailability in aquatic environments.
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Affiliation(s)
| | | | - M A Muñoz-Martín
- Department of Biology, Universidad Autónoma de Madrid Madrid, Spain
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27
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Bioremediation of Heavy Metals from Soil and Aquatic Environment: An Overview of Principles and Criteria of Fundamental Processes. SUSTAINABILITY 2015. [DOI: 10.3390/su7022189] [Citation(s) in RCA: 344] [Impact Index Per Article: 38.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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28
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Responses to oxidative and heavy metal stresses in cyanobacteria: recent advances. Int J Mol Sci 2014; 16:871-86. [PMID: 25561236 PMCID: PMC4307280 DOI: 10.3390/ijms16010871] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 12/24/2014] [Indexed: 12/24/2022] Open
Abstract
Cyanobacteria, the only known prokaryotes that perform oxygen-evolving photosynthesis, are receiving strong attention in basic and applied research. In using solar energy, water, CO2 and mineral salts to produce a large amount of biomass for the food chain, cyanobacteria constitute the first biological barrier against the entry of toxics into the food chain. In addition, cyanobacteria have the potential for the solar-driven carbon-neutral production of biofuels. However, cyanobacteria are often challenged by toxic reactive oxygen species generated under intense illumination, i.e., when their production of photosynthetic electrons exceeds what they need for the assimilation of inorganic nutrients. Furthermore, in requiring high amounts of various metals for growth, cyanobacteria are also frequently affected by drastic changes in metal availabilities. They are often challenged by heavy metals, which are increasingly spread out in the environment through human activities, and constitute persistent pollutants because they cannot be degraded. Consequently, it is important to analyze the protection against oxidative and metal stresses in cyanobacteria because these ancient organisms have developed most of these processes, a large number of which have been conserved during evolution. This review summarizes what is known regarding these mechanisms, emphasizing on their crosstalk.
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29
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Huertas MJ, López-Maury L, Giner-Lamia J, Sánchez-Riego AM, Florencio FJ. Metals in cyanobacteria: analysis of the copper, nickel, cobalt and arsenic homeostasis mechanisms. Life (Basel) 2014; 4:865-86. [PMID: 25501581 PMCID: PMC4284471 DOI: 10.3390/life4040865] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Revised: 11/27/2014] [Accepted: 12/04/2014] [Indexed: 11/16/2022] Open
Abstract
Traces of metal are required for fundamental biochemical processes, such as photosynthesis and respiration. Cyanobacteria metal homeostasis acquires an important role because the photosynthetic machinery imposes a high demand for metals, making them a limiting factor for cyanobacteria, especially in the open oceans. On the other hand, in the last two centuries, the metal concentrations in marine environments and lake sediments have increased as a result of several industrial activities. In all cases, cells have to tightly regulate uptake to maintain their intracellular concentrations below toxic levels. Mechanisms to obtain metal under limiting conditions and to protect cells from an excess of metals are present in cyanobacteria. Understanding metal homeostasis in cyanobacteria and the proteins involved will help to evaluate the use of these microorganisms in metal bioremediation. Furthermore, it will also help to understand how metal availability impacts primary production in the oceans. In this review, we will focus on copper, nickel, cobalt and arsenic (a toxic metalloid) metabolism, which has been mainly analyzed in model cyanobacterium Synechocystis sp. PCC 6803.
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Affiliation(s)
- María José Huertas
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Américo Vespucio 49, E-41092 Sevilla, Spain.
| | - Luis López-Maury
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Américo Vespucio 49, E-41092 Sevilla, Spain.
| | - Joaquín Giner-Lamia
- Systems Biology and Bioinformatics Laboratory, IBB-CBME, University of Algarve, Campus de Gambelas, 8005-139 Faro, Portugal.
| | - Ana María Sánchez-Riego
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Américo Vespucio 49, E-41092 Sevilla, Spain.
| | - Francisco Javier Florencio
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Américo Vespucio 49, E-41092 Sevilla, Spain.
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Improved protein overexpression and purification strategies for structural studies of cyanobacterial metal-responsive transcription factor, SmtB from marine Synechococcus sp. PCC 7002. Protein J 2014; 32:626-34. [PMID: 24264463 DOI: 10.1007/s10930-013-9525-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
There are structural and functional differences in SmtB homologs, metal-responsive transcription factors responsible for sensing of excess heavy metal ions in marine and freshwater cyanobacterial strains. The structure of SmtB from freshwater Synechococcus sp. strain PCC 7942 is elucidated with nuclear magnetic resonance (NMR) and crystallography techniques. But knowledge about the functioning of SmtB homologs from marine species is limited till date. To enable NMR spectroscopic studies for investigating structural and functional aspects, modified protocols with higher yields of isotopically labeled SmtB, from marine species like Synechococcus sp. PCC 7002 are essential. In this study, smtB gene was cloned from genome of Synechococcus sp. PCC 7002 and overexpression protocol for recombinant SmtB was standardized in Escherichia coli containing T7 RNA polymerase/promoter system. Further, the protocol for large-scale production, isotope labeling with (15)N, and purification of recombinant SmtB in E. coli BL21(DE3)/pLysS cells was developed. Purified recombinant protein was successfully used for NMR spectroscopy experiments. These results indicate that the overexpression technique now developed is applicable to the structural and functional studies for the proteins being homologous to cyanobacterial SmtB from Synechococcus sp. PCC 7002.
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Chudobova D, Dostalova S, Blazkova I, Michalek P, Ruttkay-Nedecky B, Sklenar M, Nejdl L, Kudr J, Gumulec J, Tmejova K, Konecna M, Vaculovicova M, Hynek D, Masarik M, Kynicky J, Kizek R, Adam V. Effect of ampicillin, streptomycin, penicillin and tetracycline on metal resistant and non-resistant Staphylococcus aureus. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2014; 11:3233-55. [PMID: 24651395 PMCID: PMC3987032 DOI: 10.3390/ijerph110303233] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Revised: 02/18/2014] [Accepted: 02/24/2014] [Indexed: 12/29/2022]
Abstract
There is an arising and concerning issue in the field of bacterial resistance, which is confirmed by the number of deaths associated with drug-resistant bacterial infections. The aim of this study was to compare the effects of antibiotics on Staphylococcus aureus non-resistant strain and strains resistant to cadmium or lead ions. Metal resistant strains were created by the gradual addition of 2 mM solution of metal ions (cadmium or lead) to the S. aureus culture. An increasing antimicrobial effect of ampicillin, streptomycin, penicillin and tetracycline (0, 10, 25, 50, 75, 150, 225 and 300 µM) on the resistant strains was observed using a method of growth curves. A significant growth inhibition (compared to control) of cadmium resistant cells was observed in the presence of all the four different antibiotics. On the other hand, the addition of streptomycin and ampicillin did not inhibit the growth of lead resistant strain. Other antibiotics were still toxic to the bacterial cells. Significant differences in the morphology of cell walls were indicated by changes in the cell shape. Our data show that the presence of metal ions in the urban environment may contribute to the development of bacterial strain resistance to other substances including antibiotics, which would have an impact on public health.
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Affiliation(s)
- Dagmar Chudobova
- Department of Chemistry and Biochemistry, Faculty of Agronomy, Mendel University in Brno, Zemedelska 1, Brno CZ-613 00, Czech Republic.
| | - Simona Dostalova
- Department of Chemistry and Biochemistry, Faculty of Agronomy, Mendel University in Brno, Zemedelska 1, Brno CZ-613 00, Czech Republic.
| | - Iva Blazkova
- Department of Chemistry and Biochemistry, Faculty of Agronomy, Mendel University in Brno, Zemedelska 1, Brno CZ-613 00, Czech Republic.
| | - Petr Michalek
- Department of Chemistry and Biochemistry, Faculty of Agronomy, Mendel University in Brno, Zemedelska 1, Brno CZ-613 00, Czech Republic.
| | - Branislav Ruttkay-Nedecky
- Department of Chemistry and Biochemistry, Faculty of Agronomy, Mendel University in Brno, Zemedelska 1, Brno CZ-613 00, Czech Republic.
| | - Matej Sklenar
- Department of Chemistry and Biochemistry, Faculty of Agronomy, Mendel University in Brno, Zemedelska 1, Brno CZ-613 00, Czech Republic.
| | - Lukas Nejdl
- Department of Chemistry and Biochemistry, Faculty of Agronomy, Mendel University in Brno, Zemedelska 1, Brno CZ-613 00, Czech Republic.
| | - Jiri Kudr
- Department of Chemistry and Biochemistry, Faculty of Agronomy, Mendel University in Brno, Zemedelska 1, Brno CZ-613 00, Czech Republic.
| | - Jaromir Gumulec
- Central European Institute of Technology, Brno University of Technology, Technicka 3058/10, Brno CZ-616 00, Czech Republic.
| | - Katerina Tmejova
- Department of Chemistry and Biochemistry, Faculty of Agronomy, Mendel University in Brno, Zemedelska 1, Brno CZ-613 00, Czech Republic.
| | - Marie Konecna
- Department of Chemistry and Biochemistry, Faculty of Agronomy, Mendel University in Brno, Zemedelska 1, Brno CZ-613 00, Czech Republic.
| | - Marketa Vaculovicova
- Department of Chemistry and Biochemistry, Faculty of Agronomy, Mendel University in Brno, Zemedelska 1, Brno CZ-613 00, Czech Republic.
| | - David Hynek
- Central European Institute of Technology, Brno University of Technology, Technicka 3058/10, Brno CZ-616 00, Czech Republic.
| | - Michal Masarik
- Central European Institute of Technology, Brno University of Technology, Technicka 3058/10, Brno CZ-616 00, Czech Republic.
| | - Jindrich Kynicky
- Karel Englis College, Sujanovo nam. 356/1, Brno CZ-602 00, Czech Republic.
| | - Rene Kizek
- Department of Chemistry and Biochemistry, Faculty of Agronomy, Mendel University in Brno, Zemedelska 1, Brno CZ-613 00, Czech Republic.
| | - Vojtech Adam
- Department of Chemistry and Biochemistry, Faculty of Agronomy, Mendel University in Brno, Zemedelska 1, Brno CZ-613 00, Czech Republic.
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32
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Jarosławiecka A, Piotrowska-Seget Z. Lead resistance in micro-organisms. Microbiology (Reading) 2014; 160:12-25. [DOI: 10.1099/mic.0.070284-0] [Citation(s) in RCA: 123] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Lead (Pb) is an element present in the environment that negatively affects all living organisms. To diminish its high toxicity, micro-organisms have developed several mechanisms that allow them to survive exposure to Pb(II). The main mechanisms of lead resistance involve adsorption by extracellular polysaccharides, cell exclusion, sequestration as insoluble phosphates, and ion efflux to the cell exterior. This review describes the various lead resistance mechanisms, and the regulation of their expression by lead binding regulatory proteins. Special attention is given to the Pbr system from Cupriavidus metallidurans CH34, which involves a unique mechanism combining efflux and lead precipitation.
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Affiliation(s)
- Anna Jarosławiecka
- Department of Microbiology, University of Silesia, Jagiellońska Street 28, Katowice 40-032, Poland
| | - Zofia Piotrowska-Seget
- Department of Microbiology, University of Silesia, Jagiellońska Street 28, Katowice 40-032, Poland
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33
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Couñago RM, Ween MP, Begg SL, Bajaj M, Zuegg J, O'Mara ML, Cooper MA, McEwan AG, Paton JC, Kobe B, McDevitt CA. Imperfect coordination chemistry facilitates metal ion release in the Psa permease. Nat Chem Biol 2013; 10:35-41. [DOI: 10.1038/nchembio.1382] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Accepted: 09/19/2013] [Indexed: 12/21/2022]
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34
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Patterson CJ, Pernil R, Dainty SJ, Chakrabarti B, Henry CE, Money VA, Foster AW, Robinson NJ. Co(ll)-detection does not follow Kco(ll) gradient: channelling in Co(ll)-sensing. Metallomics 2013; 5:352-62. [PMID: 23420021 DOI: 10.1039/c3mt20241k] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The MerR-like transcriptional activator CoaR detects surplus Co(ll) to regulate Co(ll) efflux in a cyanobacterium. This organism also has cytosolic metal-sensors from three further families represented by Zn(ll)-sensors ZiaR and Zur plus Ni(ll)-sensor InrS. Here we discover by competition with Fura-2 that CoaR has KCo(ll) weaker than 7 × 10(-8) M, which is weaker than ZiaR, Zur and InrS (KCo(ll) = 6.94 ± 1.3 × 10(-10) M; 4.56 ± 0.16 × 10(-10) M; and 7.69 ± 1.1 × 10(-9) M respectively). KCo(ll) for CoaR is also weak in the CoaR-DNA adduct. Further, Co(ll) promotes DNA-dissociation by ZiaR and DNA-association by Zur in vitro in a manner analogous to Zn(ll), as monitored by fluorescence anisotropy. After 48 h exposure to maximum non-inhibitory [Co(ll)], CoaR responds in vivo yet the two Zn(ll)-sensors do not, despite their tighter KCo(ll) and despite Co(ll) triggering allostery in ZiaR and Zur in vitro. These data imply that the two Zn(ll) sensors fail to respond because they fail to gain access to Co(ll) under these conditions in vivo. Several lines of evidence suggest that CoaR is membrane associated via a domain with sequence similarity to precorrin isomerase, an enzyme of vitamin B12 biosynthesis. Moreover, site directed mutagenesis reveals that transcriptional activation requires CoaR residues that are predicted to form hydrogen bonds to a tetrapyrrole. The Co(ll)-requiring vitamin B12 biosynthetic pathway is also membrane associated suggesting putative mechanisms by which Co(ll)-containing tetrapyrroles and/or Co(ll) ions are channelled to CoaR.
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Affiliation(s)
- Carl J Patterson
- School/Department of Biological and Biomedical Sciences, Biophysical Sciences Institute, Durham University, DH1 3LE, UK
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35
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Kondrat FDL, Kowald GR, Scarff CA, Scrivens JH, Blindauer CA. Resolution of a paradox by native mass spectrometry: facile occupation of all four metal binding sites in the dimeric zinc sensor SmtB. Chem Commun (Camb) 2013; 49:813-5. [DOI: 10.1039/c2cc38387j] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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36
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Liu M, Crosa JH. The regulator HlyU, the repeat-in-toxin gene rtxA1, and their roles in the pathogenesis of Vibrio vulnificus infections. Microbiologyopen 2012; 1:502-13. [PMID: 23233275 PMCID: PMC3535394 DOI: 10.1002/mbo3.48] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Revised: 07/27/2012] [Accepted: 08/06/2012] [Indexed: 12/19/2022] Open
Abstract
HlyU is a master regulator that plays an essential role in the virulence of the human pathogen Vibrio vulnificus. One of the most noteworthy characteristics of HlyU regulation in this organism is its positive control of the expression of the repeat-in-toxin (RtxA1) gene, one of the most important virulence factors accounting for the fulminating and damaging nature of V. vulnificus infections. In this work, we reviewed the latest studies of RtxA1 in this bacterium and highlight the mechanism of gene regulation of rtxA1 expression by HlyU under a broader gene regulatory network.
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Affiliation(s)
- Moqing Liu
- Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, Oregon 97239, USA.
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37
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Wang P, Lutton A, Olesik J, Vali H, Li X. A novel iron- and copper-binding protein in the Lyme disease spirochaete. Mol Microbiol 2012; 86:1441-51. [PMID: 23061404 DOI: 10.1111/mmi.12068] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/09/2012] [Indexed: 12/31/2022]
Abstract
Iron and copper are transition metals that can be toxic to cells due to their abilities to react with peroxide to generate hydroxyl radical. Ferritins and metallothioneins are known to sequester intracellular iron and copper respectively. The Lyme disease pathogen Borrelia burgdorferi does not require iron, but its genome encodes a ferritin-like Dps (DNA-binding protein from starved bacteria) molecule, which has been shown to be important for the spirochaete's persistence in the tick and subsequent transmission to a new host. Here, we show that the carboxyl-terminal cysteine-rich (CCR) domain of this protein functions as a copper-binding metallothionein. This novel fusion between Dps and metallothionein is unique to and conserved in all Borrelia species. We term this molecule BicA for Borrelia iron- and copper-binding protein A. An isogenic mutant lacking BicA had significantly reduced levels of iron and copper and was more sensitive to iron and copper toxicity than its parental strain. Supplementation of the medium with iron or copper rendered the spirochaete more susceptible to peroxide killing. These data suggest that an important function of BicA is to detoxify excess iron and copper the spirochaete may encounter during its natural life cycle through a tick vector and a vertebrate host.
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Affiliation(s)
- Peng Wang
- Department of Veterinary Biosciences, The Ohio State University, 1900 Coffey Road, Columbus, OH 43210, USA
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38
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Mac Aogáin M, Mooij MJ, McCarthy RR, Plower E, Wang YP, Tian ZX, Dobson A, Morrissey J, Adams C, O'Gara F. The non-classical ArsR-family repressor PyeR (PA4354) modulates biofilm formation in Pseudomonas aeruginosa. MICROBIOLOGY-SGM 2012; 158:2598-2609. [PMID: 22820840 DOI: 10.1099/mic.0.058636-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
PyeR (PA4354) is a novel member of the ArsR family of transcriptional regulators and modulates biofilm formation in Pseudomonas aeruginosa. Characterization of this regulator showed that it has negative autoregulatory properties and binds to a palindromic motif conserved among PyeR orthologues. These characteristics are in line with classical ArsR-family regulators, as is the fact that PyeR is part of an operon structure (pyeR-pyeM-xenB). However, PyeR also exhibits some atypical features in comparison with classical members of the ArsR family, as it does not harbour metal-binding motifs and does not appear to be involved in metal perception or resistance. Hence, PyeR belongs to a subgroup of non-classical ArsR-family regulators and is the second ArsR regulator shown to be involved in biofilm formation.
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Affiliation(s)
- M Mac Aogáin
- BIOMERIT Research Centre, Department of Microbiology, University College Cork, Cork, Ireland
| | - M J Mooij
- BIOMERIT Research Centre, Department of Microbiology, University College Cork, Cork, Ireland
| | - R R McCarthy
- BIOMERIT Research Centre, Department of Microbiology, University College Cork, Cork, Ireland
| | - E Plower
- BIOMERIT Research Centre, Department of Microbiology, University College Cork, Cork, Ireland
| | - Y P Wang
- National Laboratory of Plant Engineering and Protein Genetic Engineering, College of Life Science, Peking University, Beijing, PR China
| | - Z X Tian
- National Laboratory of Plant Engineering and Protein Genetic Engineering, College of Life Science, Peking University, Beijing, PR China.,BIOMERIT Research Centre, Department of Microbiology, University College Cork, Cork, Ireland
| | - A Dobson
- Department of Microbiology, University College Cork, Cork, Ireland.,Marine Biotechnology Centre, Environmental Research Institute, University College Cork, Cork, Ireland
| | - J Morrissey
- Department of Microbiology, University College Cork, Cork, Ireland.,Marine Biotechnology Centre, Environmental Research Institute, University College Cork, Cork, Ireland
| | - C Adams
- BIOMERIT Research Centre, Department of Microbiology, University College Cork, Cork, Ireland
| | - F O'Gara
- Department of Microbiology, University College Cork, Cork, Ireland.,Marine Biotechnology Centre, Environmental Research Institute, University College Cork, Cork, Ireland.,BIOMERIT Research Centre, Department of Microbiology, University College Cork, Cork, Ireland
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39
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Barnett JP, Millard A, Ksibe AZ, Scanlan DJ, Schmid R, Blindauer CA. Mining genomes of marine cyanobacteria for elements of zinc homeostasis. Front Microbiol 2012; 3:142. [PMID: 22514551 PMCID: PMC3323870 DOI: 10.3389/fmicb.2012.00142] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Accepted: 03/25/2012] [Indexed: 12/13/2022] Open
Abstract
Zinc is a recognized essential element for the majority of organisms, and is indispensable for the correct function of hundreds of enzymes and thousands of regulatory proteins. In aquatic photoautotrophs including cyanobacteria, zinc is thought to be required for carbonic anhydrase and alkaline phosphatase, although there is evidence that at least some carbonic anhydrases can be cambialistic, i.e., are able to acquire in vivo and function with different metal cofactors such as Co2+ and Cd2+. Given the global importance of marine phytoplankton, zinc availability in the oceans is likely to have an impact on both carbon and phosphorus cycles. Zinc concentrations in seawater vary over several orders of magnitude, and in the open oceans adopt a nutrient-like profile. Most studies on zinc handling by cyanobacteria have focused on freshwater strains and zinc toxicity; much less information is available on marine strains and zinc limitation. Several systems for zinc homeostasis have been characterized in the freshwater species Synechococcus sp. PCC 7942 and Synechocystis sp. PCC 6803, but little is known about zinc requirements or zinc handling by marine species. Comparative metallo-genomics has begun to explore not only the putative zinc proteome, but also specific protein families predicted to have an involvement in zinc homeostasis, including sensors for excess and limitation (SmtB and its homologs as well as Zur), uptake systems (ZnuABC), putative intracellular zinc chaperones (COG0523) and metallothioneins (BmtA), and efflux pumps (ZiaA and its homologs).
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40
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Foster AW, Patterson CJ, Pernil R, Hess CR, Robinson NJ. Cytosolic Ni(II) sensor in cyanobacterium: nickel detection follows nickel affinity across four families of metal sensors. J Biol Chem 2012; 287:12142-51. [PMID: 22356910 PMCID: PMC3320959 DOI: 10.1074/jbc.m111.338301] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Efflux of surplus Ni(II) across the outer and inner membranes of Synechocystis PCC 6803 is mediated by the Nrs system under the control of a sensor of periplasmic Ni(II), NrsS. Here, we show that the product of ORF sll0176, which encodes a CsoR/RcnR-like protein now designated InrS (for internal nickel-responsive sensor), represses nrsD (NrsD is deduced to efflux Ni(II) across the inner membrane) from a cryptic promoter between the final two ORFs in the nrs operon. Transcripts initiated from the newly identified nrsD promoter accumulate in response to nickel or cobalt but not copper, and recombinant InrS forms specific, Ni(II)-inhibited complexes with the nrsD promoter region. Metal-dependent difference spectra of Ni(II)- and Cu(I)-InrS are similar to Cu(I)-sensing CsoR and dissimilar to Ni(II)/Co(II)-sensing RcnR, consistent with factors beyond the primary coordination sphere switching metal selectivity. Competition with chelators mag-fura-2, nitrilotriacetic acid, EDTA, and EGTA estimate KD Ni(II) for the tightest site of InrS as 2.05 (±1.5) × 10−14m, and weaker KD Ni(II) for the cells' metal sensors of other types: Zn(II) co-repressor Zur, Co(II) activator CoaR, and Zn(II) derepressor ZiaR. Ni(II) transfer to InrS occurs upon addition to Ni(II) forms of each other sensor. InrS binds Ni(II) sufficiently tightly to derepress Ni(II) export at concentrations below KD Ni(II) of the other sensors.
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Affiliation(s)
- Andrew W Foster
- Biophysical Sciences Institute, Department of Chemistry, School of Biological and Biomedical Sciences, University of Durham, Durham DH1 3LE, United Kingdom
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41
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Ravikumar S, Yoo IK, Lee SY, Hong SH. A study on the dynamics of the zraP gene expression profile and its application to the construction of zinc adsorption bacteria. Bioprocess Biosyst Eng 2011; 34:1119-26. [PMID: 21674266 DOI: 10.1007/s00449-011-0562-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Accepted: 05/31/2011] [Indexed: 10/18/2022]
Abstract
Zinc ion plays essential roles in biological chemistry. Bacteria acquire Zn(2+) from the environment, and cellular concentration levels are controlled by zinc homeostasis systems. In comparison with other homeostatic systems, the ZraSR two-component system was found to be more efficient in responding to exogenous zinc concentrations. To understand the dynamic response of the bacterium ZraSR two-component system with respect to exogenous zinc concentrations, the genetic circuit of the ZraSR system was integrated with a reporter protein. This study was helpful in the construction of an E. coli system that can display selective metal binding peptides on the surface of the cell in response to exogenous zinc. The engineered bacterial system for monitoring exogenous zinc was successfully employed to detect levels of zinc as low as 0.001 mM, which directly activates the expression of chimeric ompC(t)--zinc binding peptide gene to remove zinc by adsorbing a maximum of 163.6 μmol of zinc per gram of dry cell weight. These results indicate that the engineered bacterial strain developed in the present study can sense the specific heavy metal and activates a cell surface display system that acts to remove the metal.
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Affiliation(s)
- Sambandam Ravikumar
- School of Chemical Engineering and Bioengineering, University of Ulsan, Daehakro 93, Nam-gu, Ulsan, 680-749, Republic of Korea
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42
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Micro-algal biosensors. Anal Bioanal Chem 2011; 401:581-97. [PMID: 21626188 DOI: 10.1007/s00216-011-5107-z] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2011] [Revised: 05/04/2011] [Accepted: 05/13/2011] [Indexed: 10/18/2022]
Abstract
Fighting against water pollution requires the ability to detect pollutants for example herbicides or heavy metals. Micro-algae that live in marine and fresh water offer a versatile solution for the construction of novel biosensors. These photosynthetic microorganisms are very sensitive to changes in their environment, enabling the detection of traces of pollutants. Three groups of micro-algae are described in this paper: chlorophyta, cyanobacteria, and diatoms.
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43
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Bacterial metallothioneins: past, present, and questions for the future. J Biol Inorg Chem 2011; 16:1011-24. [DOI: 10.1007/s00775-011-0790-y] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2011] [Accepted: 05/04/2011] [Indexed: 10/18/2022]
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44
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Abstract
When attempting to assess the extent and the implications of environmental pollution, it is often essential to quantify not only the total concentration of the studied contaminant but also its bioavailable fraction: higher bioavailability, often correlated with increased mobility, signifies enhanced risk but may also facilitate bioremediation. Genetically engineered microorganisms, tailored to respond by a quantifiable signal to the presence of the target chemical(s), may serve as powerful tools for bioavailability assessment. This review summarizes the current knowledge on such microbial bioreporters designed to assay metal bioavailability. Numerous bacterial metal‐sensor strains have been developed over the past 15 years, displaying very high detection sensitivities for a broad spectrum of environmentally significant metal targets. These constructs are based on the use of a relatively small number of gene promoters as the sensing elements, and an even smaller selection of molecular reporter systems; they comprise a potentially useful panel of tools for simple and cost‐effective determination of the bioavailability of heavy metals in the environment, and for the quantification of the non‐bioavailable fraction of the pollutant. In spite of their inherent advantages, however, these tools have not yet been put to actual use in the evaluation of metal bioavailability in a real environmental remediation scheme. For this to happen, acceptance by regulatory authorities is essential, as is a standardization of assay conditions.
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Affiliation(s)
- Sagi Magrisso
- Institute of life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
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45
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Sevcenco AM, Pinkse MWH, Wolterbeek HT, Verhaert PDEM, Hagen WR, Hagedoorn PL. Exploring the microbial metalloproteome using MIRAGE. Metallomics 2011; 3:1324-30. [DOI: 10.1039/c1mt00154j] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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46
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Waldron KJ, Firbank SJ, Dainty SJ, Pérez-Rama M, Tottey S, Robinson NJ. Structure and metal loading of a soluble periplasm cuproprotein. J Biol Chem 2010; 285:32504-11. [PMID: 20702411 DOI: 10.1074/jbc.m110.153080] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A copper-trafficking pathway was found to enable Cu(2+) occupancy of a soluble periplasm protein, CucA, even when competing Zn(2+) is abundant in the periplasm. Here, we solved the structure of CucA (a new cupin) and found that binding of Cu(2+), but not Zn(2+), quenches the fluorescence of Trp(165), which is adjacent to the metal site. Using this fluorescence probe, we established that CucA becomes partly occupied by Zn(2+) following exposure to equimolar Zn(2+) and Cu(2+). Cu(2+)-CucA is more thermodynamically stable than Zn(2+)-CucA but k((Zn→Cu)exchange) is slow, raising questions about how the periplasm contains solely the Cu(2+) form. We discovered that a copper-trafficking pathway involving two copper transporters (CtaA and PacS) and a metallochaperone (Atx1) is obligatory for Cu(2+)-CucA to accumulate in the periplasm. There was negligible CucA protein in the periplasm of ΔctaA cells, but the abundance of cucA transcripts was unaltered. Crucially, ΔctaA cells overaccumulate low M(r) copper complexes in the periplasm, and purified apoCucA can readily acquire Cu(2+) from ΔctaA periplasm extracts, but in vivo apoCucA fails to come into contact with these periplasmic copper pools. Instead, copper traffics via a cytoplasmic pathway that is coupled to CucA translocation to the periplasm.
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Affiliation(s)
- Kevin J Waldron
- Institute for Cell and Molecular Biosciences, University of Newcastle Medical School, Newcastle upon Tyne NE2 4HH, United Kingdom
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47
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Stout L, Nüsslein K. Biotechnological potential of aquatic plant-microbe interactions. Curr Opin Biotechnol 2010; 21:339-45. [PMID: 20494570 DOI: 10.1016/j.copbio.2010.04.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2010] [Revised: 04/13/2010] [Accepted: 04/13/2010] [Indexed: 11/18/2022]
Abstract
The rhizosphere in terrestrial systems is the region of soil surrounding plant roots where there is increased microbial activity; in aquatic plants, this definition may be less clear because of diffusion of nutrients in water, but there is still a zone of influence by plant roots in this environment [1]. Within that zone chemical conditions differ from those of the surrounding environment as a consequence of a range of processes that were induced either directly by the activity of plant roots or by the activity of rhizosphere microflora. Recently, there are a number of new studies related to rhizospheres of aquatic plants and specifically their increased potential for remediation of contaminants, especially remediation of metals through aquatic plant-microbial interaction.
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Affiliation(s)
- L Stout
- Department of Biology, Southern Connecticut State University, New Haven, CT 06515, United States.
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Osman D, Cavet JS. Bacterial metal-sensing proteins exemplified by ArsR-SmtB family repressors. Nat Prod Rep 2010; 27:668-80. [PMID: 20442958 DOI: 10.1039/b906682a] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Detecting deficiency and excess of different metal ions is fundamental for every organism. Our understanding of how metals are detected by bacteria is exceptionally well advanced, and multiple families of cytoplasmic DNA-binding, metal-sensing transcriptional regulators have been characterised(ArsR-SmtB, MerR, CsoR-RcnR, CopY, DtxR, Fur, NikR). Some of the sensors regulate a single gene while others act globally controlling transcription of regulons. They not only modulate the expression of genes directly associated with metal homeostasis, but can also alter metabolism to reduce the cellular demand for metals in short supply. Different representatives of each of the sensor families can regulate gene expression in response to different metals, and the residues that form the sensory metal-binding sites have been defined in a number of these proteins. Indeed, in the case of theArsR-SmtB family, multiple distinct metal-sensing motifs (and one non-metal-sensing motif) have been identified which correlate with the detection of different metals. This review summarises the different families of bacterial metal-sensing transcriptional regulators and discusses current knowledge regarding the mechanisms of metal-regulated gene expression and the structural features of sensory metal-binding sites focusing on the ArsR-SmtB family. In addition, recent progress in understanding the principles governing the ability of the sensors to detect specific metals within a cell and the coordination of the different sensors to control cellular metal levels is discussed.
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Affiliation(s)
- Deenah Osman
- University of Manchester, Manchester, M13 9PT, UK
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Banci L, Bertini I, McGreevy KS, Rosato A. Molecular recognition in copper trafficking. Nat Prod Rep 2010; 27:695-710. [DOI: 10.1039/b906678k] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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Bofill R, Orihuela R, Romagosa M, Domènech J, Atrian S, Capdevila M. Caenorhabditis elegans metallothionein isoform specificity--metal binding abilities and the role of histidine in CeMT1 and CeMT2. FEBS J 2009; 276:7040-56. [PMID: 19860833 DOI: 10.1111/j.1742-4658.2009.07417.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Two metallothionein (MT) isoforms have been identified in the model nematode Caenorhabditis elegans: CeMT1 and CeMT2, comprising two polypeptides that are 75 and 63 residues in length, respectively. Both isoforms encompass a conserved cysteine pattern (19 in CeMT1 and 18 in CeMT2) and, most significantly, as a result of their coordinative potential, CeMT1 includes four histidines, whereas CeMT2 has only one. In the present study, we present a comprehensive and comparative analysis of the metal [Zn(II), Cd(II) and Cu(I)] binding abilities of CeMT1 and CeMT2, performed through spectroscopic and spectrometric characterization of the recombinant metal-MT complexes synthesized for wild-type isoforms (CeMT1 and CeMT2), their separate N- and C-terminal moieties (NtCeMT1, CtCeMT1, NtCeMT2 and CtCeMT2) and a DeltaHisCeMT2 mutant. The corresponding in vitro Zn/Cd- and Zn/Cu-replacement and acidification/renaturalization processes have also been studied, as well as protein modification strategies that make it possible to identify and quantify the contribution of the histidine residues to metal coordination. Overall, the data obtained in the present study are consistent with a scenario where both isoforms exhibit a clear preference for divalent metal ion binding, rather than for Cu coordination, although this preference is more pronounced towards cadmium for CeMT2, whereas it is markedly clearer towards Zn for CeMT1. The presence of histidines in these MTs is revealed to be decisive for their coordination performance. In CeMT1, they contribute to the binding of a seventh Zn(II) ion in relation to the M(II)(6)-CeMT2 complexes, both when synthesized in the presence of supplemented Zn(II) or Cd(II). In CeMT2, the unique C-terminal histidine abolishes the Cu-thionein character that this isoform would otherwise exhibit.
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Affiliation(s)
- Roger Bofill
- Departament de Química, Facultat de Ciències, Universitat Autònoma de Barcelona, Spain
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