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Mehić S, Saltikov C. Genome sequence and characterisation of a freshwater photoarsenotroph, Cereibacter azotoformans strain ORIO, isolated from sediments capable of cyclic light-dark arsenic oxidation and reduction. Environ Microbiol 2023; 25:3738-3752. [PMID: 37974504 DOI: 10.1111/1462-2920.16542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Accepted: 11/01/2023] [Indexed: 11/19/2023]
Abstract
A freshwater photosynthetic arsenite-oxidizing bacterium, Cereibacter azotoformans strain ORIO, was isolated from Owens River, CA, USA. The waters from Owens River are elevated in arsenic and serve as the headwaters to the Los Angeles Aqueduct. The complete genome sequence of strain ORIO is 4.8 Mb genome (68% G + C content) and comprises two chromosomes and six plasmids. Taxonomic analysis placed ORIO within the Cereibacter genus (formerly Rhodobacter). The ORIO genome contains arxB2 AB1 CD (encoding an arsenite oxidase), arxXSR (regulators) and several ars arsenic resistance genes all co-localised on a 136 kb plasmid, named pORIO3. Phylogenetic analysis of ArxA, the molybdenum-containing arsenite oxidase catalytic subunit, demonstrated photoarsenotrophy is likely to occur within members of the Alphaproteobacteria. ORIO is a mixotroph, oxidises arsenite to arsenate (As(V)) photoheterotrophically, and expresses arxA in cultures grown with arsenite. Further ecophysiology studies with Owens River sediment demonstrated the interconversion of arsenite and As(V) was dependent on light-dark cycling. arxA and arrA (As(V) respiratory reductase) genes were detected in the light-dark cycled sediment metagenomes suggesting syntrophic interactions among arsenotrophs. This work establishes C. azotoformans str. ORIO as a new model organism for studying photoarsenotrophy and light-dark arsenic biogeochemical cycling.
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Affiliation(s)
- Sanjin Mehić
- Department of Microbiology and Environmental Toxicology, University of California Santa Cruz, Santa Cruz, California, USA
| | - Chad Saltikov
- Department of Microbiology and Environmental Toxicology, University of California Santa Cruz, Santa Cruz, California, USA
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Mathur M, Rawat N, Saxena T, Khandelwal R, Jain N, Sharma MK, Mohan MK, Bhatnagar P, Flora SJS, Kaushik P. Effect of Arsenic on Fluoride Tolerance in Microbacterium paraoxydans Strain IR-1. TOXICS 2023; 11:945. [PMID: 37999597 PMCID: PMC10675054 DOI: 10.3390/toxics11110945] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2023] [Revised: 10/30/2023] [Accepted: 11/09/2023] [Indexed: 11/25/2023]
Abstract
Fluoride (F) and arsenic (As) are two major contaminants of water and soil systems around the globe, causing potential toxicity to humans, plants, animals, and microbes. These contaminated soil systems can be restored by microorganisms that can tolerate toxic stress and provide rapid mineralization of soil, organic matter, and contaminants, using various tolerance mechanisms. Thus, the present study was undertaken with the arsenic hyper-tolerant bacterium Microbacterium paraoxydans strain IR-1 to determine its tolerance and toxicity to increasing doses of fluoride, either individually or in combination with arsenic, in terms of growth inhibition using a toxicity unit model. The minimum inhibitory concentration (MIC)and half maximal inhibitory concentration (IC50) values for fluoride increased, from 9 g/L to 11 g/L and from 5.91 ± 0.1 g/L to 6.32 ± 0.028 g/L, respectively, in the combination (F + As) group. The statistical comparison of observed and expected additive toxicities, with respect to toxicity unit (TU difference), using Student's t-test, was found to be highly significant (p < 0.001). This suggests the antagonistic effect of arsenic on fluoride toxicity to the strain IR-1. The unique stress tolerance of IR-1 ensures its survival as well as preponderance in fluoride and arsenic co-contaminated sites, thus paving the way for its possible application in the natural or artificial remediation of toxicant-exposed degraded soil systems.
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Affiliation(s)
- Megha Mathur
- Applied Microbiology Laboratory, Centre for Rural Development and Technology, Indian Institute of Technology, Delhi 110016, India;
| | - Neha Rawat
- Department of Life Sciences, IIS University, Mansarovar, Jaipur 302020, India (P.B.)
| | - Tanushree Saxena
- Department of Life Sciences, IIS University, Mansarovar, Jaipur 302020, India (P.B.)
| | - Renu Khandelwal
- Centre for Advanced Studies, Department of Zoology, University of Rajasthan, Jaipur 302004, India
| | - Neha Jain
- Centre for Advanced Studies, Department of Zoology, University of Rajasthan, Jaipur 302004, India
| | - Mukesh K. Sharma
- Department of Zoology, S.P.C., Government College, Ajmer 305001, India
| | - Medicherla K. Mohan
- Department of Biotechnology and Bioinformatics, Birla Institute of Scientific Research, C Scheme, Jaipur 302001, India;
| | - Pradeep Bhatnagar
- Department of Life Sciences, IIS University, Mansarovar, Jaipur 302020, India (P.B.)
| | - Swaran J. S. Flora
- National Institute of Pharmaceutical Education and Research-Raebareli, Lucknow 226002, India
| | - Pallavi Kaushik
- Centre for Advanced Studies, Department of Zoology, University of Rajasthan, Jaipur 302004, India
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Mohsin H, Shafique M, Zaid M, Rehman Y. Microbial biochemical pathways of arsenic biotransformation and their application for bioremediation. Folia Microbiol (Praha) 2023:10.1007/s12223-023-01068-6. [PMID: 37326815 DOI: 10.1007/s12223-023-01068-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2022] [Accepted: 05/19/2023] [Indexed: 06/17/2023]
Abstract
Arsenic is a ubiquitous toxic metalloid, the concentration of which is beyond WHO safe drinking water standards in many areas of the world, owing to many natural and anthropogenic activities. Long-term exposure to arsenic proves lethal for plants, humans, animals, and even microbial communities in the environment. Various sustainable strategies have been developed to mitigate the harmful effects of arsenic which include several chemical and physical methods, however, bioremediation has proved to be an eco-friendly and inexpensive technique with promising results. Many microbes and plant species are known for arsenic biotransformation and detoxification. Arsenic bioremediation involves different pathways such as uptake, accumulation, reduction, oxidation, methylation, and demethylation. Each of these pathways has a certain set of genes and proteins to carry out the mechanism of arsenic biotransformation. Based on these mechanisms, various studies have been conducted for arsenic detoxification and removal. Genes specific for these pathways have also been cloned in several microorganisms to enhance arsenic bioremediation. This review discusses different biochemical pathways and the associated genes which play important roles in arsenic redox reactions, resistance, methylation/demethylation, and accumulation. Based on these mechanisms, new methods can be developed for effective arsenic bioremediation.
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Affiliation(s)
- Hareem Mohsin
- Department of Life Sciences, School of Science, University of Management and Technology, Lahore, Pakistan
| | - Maria Shafique
- Institute of Microbiology and Molecular Genetics, University of the Punjab, Quaid-e-Azam Campus, Lahore, Pakistan
| | - Muhammad Zaid
- Department of Life Sciences, School of Science, University of Management and Technology, Lahore, Pakistan
| | - Yasir Rehman
- Department of Life Sciences, School of Science, University of Management and Technology, Lahore, Pakistan.
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Raturi G, Chaudhary A, Rana V, Mandlik R, Sharma Y, Barvkar V, Salvi P, Tripathi DK, Kaur J, Deshmukh R, Dhar H. Microbial remediation and plant-microbe interaction under arsenic pollution. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 864:160972. [PMID: 36566865 DOI: 10.1016/j.scitotenv.2022.160972] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 12/11/2022] [Accepted: 12/12/2022] [Indexed: 06/17/2023]
Abstract
Arsenic contamination in aquatic and terrestrial ecosystem is a serious environmental issue. Both natural and anthropogenic processes can introduce it into the environment. The speciation of the As determine the level of its toxicity. Among the four oxidation states of As (-3, 0, +3, and + 5), As(III) and As(V) are the common species found in the environment, As(III) being the more toxic with adverse impact on the plants and animals including human health. Therefore, it is very necessary to remediate arsenic from the polluted water and soil. Different physicochemical as well as biological strategies can be used for the amelioration of arsenic polluted soil. Among the microbial approaches, oxidation of arsenite, methylation of arsenic, biosorption, bioprecipitation and bioaccumulation are the promising transformation activities in arsenic remediation. The purpose of this review is to discuss the significance of the microorganisms in As toxicity amelioration in soil, factors affecting the microbial remediation, interaction of the plants with As resistant bacteria, and the effect of microorganisms on plant arsenic tolerance mechanism. In addition, the exploration of genetic engineering of the bacteria has a huge importance in bioremediation strategies, as the engineered microbes are more potent in terms of remediation activity along with quick adaptively in As polluted sites.
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Affiliation(s)
- Gaurav Raturi
- National Agri-Food Biotechnology Institute (NABI), Mohali, India; Department of Biotechnology, Panjab University, Chandigarh, India
| | - Anchal Chaudhary
- National Agri-Food Biotechnology Institute (NABI), Mohali, India; Department of Biotechnology, Panjab University, Chandigarh, India
| | - Varnika Rana
- National Agri-Food Biotechnology Institute (NABI), Mohali, India
| | - Rushil Mandlik
- National Agri-Food Biotechnology Institute (NABI), Mohali, India; Department of Biotechnology, Panjab University, Chandigarh, India
| | - Yogesh Sharma
- National Agri-Food Biotechnology Institute (NABI), Mohali, India
| | - Vitthal Barvkar
- Department of Botany, Savitribai Phule Pune University, Pune, India
| | - Prafull Salvi
- National Agri-Food Biotechnology Institute (NABI), Mohali, India
| | | | - Jagdeep Kaur
- Department of Biotechnology, Panjab University, Chandigarh, India
| | - Rupesh Deshmukh
- National Agri-Food Biotechnology Institute (NABI), Mohali, India; Plaksha University, SAS Nagar, Punjab, India; Department of Biotechnology, Central University of Haryana, Mahendragarh, Haryana, India.
| | - Hena Dhar
- National Agri-Food Biotechnology Institute (NABI), Mohali, India.
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Phylogenomics reveals the basis of adaptation of Pseudorhizobium species to extreme environments and supports a taxonomic revision of the genus. Syst Appl Microbiol 2020; 44:126165. [PMID: 33360413 DOI: 10.1016/j.syapm.2020.126165] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2019] [Revised: 11/10/2020] [Accepted: 11/11/2020] [Indexed: 11/21/2022]
Abstract
The family Rhizobiaceae includes many genera of soil bacteria, often isolated for their association with plants. Herein, we investigate the genomic diversity of a group of Rhizobium species and unclassified strains isolated from atypical environments, including seawater, rock matrix or polluted soil. Based on whole-genome similarity and core genome phylogeny, we show that this group corresponds to the genus Pseudorhizobium. We thus reclassify Rhizobium halotolerans, R. marinum, R. flavum and R. endolithicum as P. halotolerans sp. nov., P. marinum comb. nov., P. flavum comb. nov. and P. endolithicum comb. nov., respectively, and show that P. pelagicum is a synonym of P. marinum. We also delineate a new chemolithoautotroph species, P. banfieldiae sp. nov., whose type strain is NT-26T (=DSM 106348T=CFBP 8663T). This genome-based classification was supported by a chemotaxonomic comparison, with increasing taxonomic resolution provided by fatty acid, protein and metabolic profiles. In addition, we used a phylogenetic approach to infer scenarios of duplication, horizontal transfer and loss for all genes in the Pseudorhizobium pangenome. We thus identify the key functions associated with the diversification of each species and higher clades, shedding light on the mechanisms of adaptation to their respective ecological niches. Respiratory proteins acquired at the origin of Pseudorhizobium were combined with clade-specific genes to enable different strategies for detoxification and nutrition in harsh, nutrient-poor environments.
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Shi K, Wang Q, Wang G. Microbial Oxidation of Arsenite: Regulation, Chemotaxis, Phosphate Metabolism and Energy Generation. Front Microbiol 2020; 11:569282. [PMID: 33072028 PMCID: PMC7533571 DOI: 10.3389/fmicb.2020.569282] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 08/21/2020] [Indexed: 12/11/2022] Open
Abstract
Arsenic (As) is a metalloid that occurs widely in the environment. The biological oxidation of arsenite [As(III)] to arsenate [As(V)] is considered a strategy to reduce arsenic toxicity and provide energy. In recent years, research interests in microbial As(III) oxidation have been growing, and related new achievements have been revealed. This review focuses on the highlighting of the novel regulatory mechanisms of bacterial As(III) oxidation, the physiological relevance of different arsenic sensing systems and functional relationship between microbial As(III) oxidation and those of chemotaxis, phosphate uptake, carbon metabolism and energy generation. The implication to environmental bioremediation applications of As(III)-oxidizing strains, the knowledge gaps and perspectives are also discussed.
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Affiliation(s)
- Kaixiang Shi
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Qian Wang
- Department of Microbiology and Immunology, Montana State University, Bozeman, MT, United States
| | - Gejiao Wang
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
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Lipa P, Janczarek M. Phosphorylation systems in symbiotic nitrogen-fixing bacteria and their role in bacterial adaptation to various environmental stresses. PeerJ 2020; 8:e8466. [PMID: 32095335 PMCID: PMC7020829 DOI: 10.7717/peerj.8466] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Accepted: 12/27/2019] [Indexed: 12/23/2022] Open
Abstract
Symbiotic bacteria, commonly called rhizobia, lead a saprophytic lifestyle in the soil and form nitrogen-fixing nodules on legume roots. During their lifecycle, rhizobia have to adapt to different conditions prevailing in the soils and within host plants. To survive under these conditions, rhizobia fine-tune the regulatory machinery to respond rapidly and adequately to environmental changes. Symbiotic bacteria play an essential role in the soil environment from both ecological and economical point of view, since these bacteria provide Fabaceae plants (legumes) with large amounts of accessible nitrogen as a result of symbiotic interactions (i.e., rhizobia present within the nodule reduce atmospheric dinitrogen (N2) to ammonia, which can be utilized by plants). Because of its restricted availability in the soil, nitrogen is one of the most limiting factors for plant growth. In spite of its high content in the atmosphere, plants are not able to assimilate it directly in the N2 form. During symbiosis, rhizobia infect host root and trigger the development of specific plant organ, the nodule. The aim of root nodule formation is to ensure a microaerobic environment, which is essential for proper activity of nitrogenase, i.e., a key enzyme facilitating N2 fixation. To adapt to various lifestyles and environmental stresses, rhizobia have developed several regulatory mechanisms, e.g., reversible phosphorylation. This key mechanism regulates many processes in both prokaryotic and eukaryotic cells. In microorganisms, signal transduction includes two-component systems (TCSs), which involve membrane sensor histidine kinases (HKs) and cognate DNA-binding response regulators (RRs). Furthermore, regulatory mechanisms based on phosphoenolopyruvate-dependent phosphotranspherase systems (PTSs), as well as alternative regulatory pathways controlled by Hanks-type serine/threonine kinases (STKs) and serine/threonine phosphatases (STPs) play an important role in regulation of many cellular processes in both free-living bacteria and during symbiosis with the host plant (e.g., growth and cell division, envelope biogenesis, biofilm formation, response to stress conditions, and regulation of metabolism). In this review, we summarize the current knowledge of phosphorylation systems in symbiotic nitrogen-fixing bacteria, and their role in the physiology of rhizobial cells and adaptation to various environmental conditions.
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Affiliation(s)
- Paulina Lipa
- Department of Genetics and Microbiology, Institute of Biological Sciences, Maria Curie-Sklodowska University Lublin, Lublin, Poland
| | - Monika Janczarek
- Department of Genetics and Microbiology, Institute of Biological Sciences, Maria Curie-Sklodowska University Lublin, Lublin, Poland
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Badilla C, Osborne TH, Cole A, Watson C, Djordjevic S, Santini JM. A new family of periplasmic-binding proteins that sense arsenic oxyanions. Sci Rep 2018; 8:6282. [PMID: 29674678 PMCID: PMC5908839 DOI: 10.1038/s41598-018-24591-w] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Accepted: 04/06/2018] [Indexed: 01/21/2023] Open
Abstract
Arsenic contamination of drinking water affects more than 140 million people worldwide. While toxic to humans, inorganic forms of arsenic (arsenite and arsenate), can be used as energy sources for microbial respiration. AioX and its orthologues (ArxX and ArrX) represent the first members of a new sub-family of periplasmic-binding proteins that serve as the first component of a signal transduction system, that’s role is to positively regulate expression of arsenic metabolism enzymes. As determined by X-ray crystallography for AioX, arsenite binding only requires subtle conformational changes in protein structure, providing insights into protein-ligand interactions. The binding pocket of all orthologues is conserved but this alone is not sufficient for oxyanion selectivity, with proteins selectively binding either arsenite or arsenate. Phylogenetic evidence, clearly demonstrates that the regulatory proteins evolved together early in prokaryotic evolution and had a separate origin from the metabolic enzymes whose expression they regulate.
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Affiliation(s)
- Consuelo Badilla
- Institute of Structural & Molecular Biology, Division of Biosciences, University College London, London, WC1E 6BT, UK
| | - Thomas H Osborne
- Institute of Structural & Molecular Biology, Division of Biosciences, University College London, London, WC1E 6BT, UK
| | - Ambrose Cole
- Institute of Structural & Molecular Biology, Department of Biological Sciences, Birkbeck College, University of London, WC1E 7HX, London, UK
| | - Cameron Watson
- Institute of Structural & Molecular Biology, Division of Biosciences, University College London, London, WC1E 6BT, UK
| | - Snezana Djordjevic
- Institute of Structural & Molecular Biology, Division of Biosciences, University College London, London, WC1E 6BT, UK.
| | - Joanne M Santini
- Institute of Structural & Molecular Biology, Division of Biosciences, University College London, London, WC1E 6BT, UK.
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Corsini PM, Walker KT, Santini JM. Expression of the arsenite oxidation regulatory operon in Rhizobium sp. str. NT-26 is under the control of two promoters that respond to different environmental cues. Microbiologyopen 2017; 7:e00567. [PMID: 29250936 PMCID: PMC6011840 DOI: 10.1002/mbo3.567] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Revised: 10/31/2017] [Accepted: 11/03/2017] [Indexed: 12/04/2022] Open
Abstract
Rhizobium sp. str. NT‐26 is a Gram‐negative facultative chemolithoautotrophic arsenite oxidizer that has been used as a model organism to study various aspects of arsenite oxidation including the regulation of arsenite oxidation. The three regulatory genes, aioX, aioS, and aioR, are cotranscribed when NT‐26 was grown in the presence or absence of arsenite. The aioXSR operon is upregulated in stationary phase but not by the presence of arsenite in the growth medium. The two transcription start sites upstream of aioX were determined which led to the identification of two promoters, the housekeeping promoter RpoD and the growth‐phase‐dependent promoter RpoE2. Promoter–lacZ fusions confirmed their constitutive and stationary phase expressions. The involvement of the NT‐26 sigma factor RpoE2 in acting on the NT‐26 RpoE2 promoter was confirmed in vivo in Escherichia coli, which lacks a rpoE2 homolog, using a strain carrying both the promoter–lacZ fusion and the NT‐26 rpoE2 gene. An in silico approach was used to search for other RpoE2 promoters and AioR‐binding motifs and led to the identification of other genes that could be regulated by these proteins including those involved in quorum sensing, chemotaxis, and motility expanding the signaling networks important for the microbial metabolism of arsenite.
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Affiliation(s)
- Paula M Corsini
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London, UK
| | - Kenneth T Walker
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London, UK
| | - Joanne M Santini
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London, UK
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