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Gao H, Guo Z, He X, Yang J, Jiang L, Yang A, Xiao X, Xu R. Stress mitigation mechanism of rice leaf microbiota amid atmospheric deposition of heavy metals. CHEMOSPHERE 2024; 362:142680. [PMID: 38908447 DOI: 10.1016/j.chemosphere.2024.142680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2024] [Revised: 06/01/2024] [Accepted: 06/20/2024] [Indexed: 06/24/2024]
Abstract
Leaf microbiota have been extensively applied in the biological control of plant diseases, but their crucial roles in mitigating atmospheric heavy metal (HM) deposition and promoting plant growth remain poorly understood. This study demonstrates that elevated atmospheric HM deposition on rice leaves significantly shapes distinct epiphytic and endophytic microbiota across all growth stages. HM stress consistently leads to the dominance of epiphytic Pantoea and endophytic Microbacterium in rice leaves, particularly during the booting and filling stages. Leaf-bound HMs stimulate the differentiation of specialized microbial communities in both endophytic and epiphytic compartments, thereby regulating leaf microbial interactions. Metagenomic binning retrieved high-quality genomes of keystone leaf microorganisms, indicating their potential for essential metabolic functions. Notably, Pantoea and Microbacterium show significant HM resistance, plant growth-promoting capabilities, and diverse element cycling functions. They possess genes associated with metal(loid) resistance, such as ars and czc, suggesting their ability to detoxify arsenic(As) and cadmium(Cd). They also support carbon, nitrogen, and sulfur cycling, with genes linked to carbon fixation, nitrogen fixation, and sulfur reduction. Additionally, these bacteria may enhance plant stress resistance and growth by producing antioxidants, phytohormones, and other beneficial compounds, potentially improving HM stress tolerance and nutrient availability in rice plants. This study shows that atmospheric HMs affect rice leaf microbial communities, prompting plants to seek microbial help to combat stress. The unique composition and metabolic potential of rice leaf microbiota offer a novel perspective for mitigating adverse stress induced by atmospheric HM deposition. This contributes to the utilization of leaf microbiota to alleviate the negative impact of heavy metal deposition on rice development and food security.
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Affiliation(s)
- Hanbing Gao
- Institute of Environmental Engineering, School of Metallurgy and Environment, Central South University, Changsha, 410083, PR China
| | - Zhaohui Guo
- Institute of Environmental Engineering, School of Metallurgy and Environment, Central South University, Changsha, 410083, PR China
| | - Xiao He
- Institute of Environmental Engineering, School of Metallurgy and Environment, Central South University, Changsha, 410083, PR China
| | - Jinbo Yang
- Institute of Environmental Engineering, School of Metallurgy and Environment, Central South University, Changsha, 410083, PR China
| | - Li Jiang
- Institute of Environmental Engineering, School of Metallurgy and Environment, Central South University, Changsha, 410083, PR China
| | - Aiping Yang
- Institute of Environmental Engineering, School of Metallurgy and Environment, Central South University, Changsha, 410083, PR China
| | - Xiyuan Xiao
- Institute of Environmental Engineering, School of Metallurgy and Environment, Central South University, Changsha, 410083, PR China
| | - Rui Xu
- Institute of Environmental Engineering, School of Metallurgy and Environment, Central South University, Changsha, 410083, PR China.
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Diba F, Hoque MN, Rahman MS, Haque F, Rahman KMJ, Moniruzzaman M, Khan M, Hossain MA, Sultana M. Metagenomic and culture-dependent approaches unveil active microbial community and novel functional genes involved in arsenic mobilization and detoxification in groundwater. BMC Microbiol 2023; 23:241. [PMID: 37648982 PMCID: PMC10466822 DOI: 10.1186/s12866-023-02980-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Accepted: 08/14/2023] [Indexed: 09/01/2023] Open
Abstract
BACKGROUND Arsenic (As) and its species are major pollutants in ecological bodied including groundwater in Bangladesh rendering serious public health concern. Bacteria with arsenotrophic genes have been found in the aquifer, converting toxic arsenite [As (III)] to less toxic arsenate [As (V)] that is easily removed using chemical and biological trappers. In this study, genomic and metagenomic approaches parallel to culture-based assay (Graphical abstract) have made it possible to decipher phylogenetic diversity of groundwater arsenotrophic microbiomes along with elucidation of their genetic determinants. RESULTS Seventy-two isolates were retrieved from six As-contaminated (average As concentration of 0.23 mg/L) groundwater samples from Munshiganj and Chandpur districts of Bangladesh. Twenty-three isolates harbored arsenite efflux pump (arsB) gene with high abundance, and ten isolates possessing arsenite oxidase (aioA) gene, with a wide range of minimum inhibitory concentration, MICAs (2 to 32 mM), confirming their role in arsenite metabolism. There was considerable heterogeneity in species richness and microbial community structure. Microbial taxa from Proteobacteria, Firmicutes and Acidobacteria dominated these diversities. Through these combinatorial approaches, we have identified potential candidates such as, Pseudomonas, Acinetobacter, Stenotrophomonas, Achromobacter, Paraburkholderia, Comamonas and Klebsiella and associated functional genes (arsB, acr3, arsD, arsH, arsR) that could significantly contribute to arsenite detoxification, accumulation, and immobilization. CONCLUSIONS Culture-dependent and -independent shotgun metagenomic investigation elucidated arsenotrophic microbiomes and their functions in As biogeochemical transformation. These findings laid a foundation for further large-scale researches on the arsenotrophic microbiomes and their concurrent functions in As biogeochemical transformation in As-contaminated areas of Bangladesh and beyond.
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Affiliation(s)
- Farzana Diba
- Department of Microbiology, University of Dhaka, Dhaka, 1000, Bangladesh
- Institute of Tissue Banking and Biomaterial Research, Atomic Energy Research Establishment, Savar, Dhaka, 1349, Bangladesh
| | - M Nazmul Hoque
- Department of Gynecology, Obstetrics and Reproductive Health, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur, 1706, Bangladesh
| | - M Shaminur Rahman
- Department of Microbiology, Jashore University of Science and Technology, Jashore, 7408, Bangladesh
| | - Farhana Haque
- Department of Microbiology, University of Dhaka, Dhaka, 1000, Bangladesh
| | | | - Md Moniruzzaman
- Bangladesh Reference Institute for Chemical Measurements (BRiCM), Dr. Qudrat-E-Khuda Road, Dhanmondi, Dhaka, 1205, Bangladesh
| | - Mala Khan
- Bangladesh Reference Institute for Chemical Measurements (BRiCM), Dr. Qudrat-E-Khuda Road, Dhanmondi, Dhaka, 1205, Bangladesh
| | - M Anwar Hossain
- Department of Microbiology, University of Dhaka, Dhaka, 1000, Bangladesh
- Present address: Jashore University of Science and Technology, Jashore, 7408, Bangladesh
| | - Munawar Sultana
- Department of Microbiology, University of Dhaka, Dhaka, 1000, Bangladesh.
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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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Prosenkov A, Cagnon C, Gallego JLR, Pelaez AI. The microbiome of a brownfield highly polluted with mercury and arsenic. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2023; 323:121305. [PMID: 36804142 DOI: 10.1016/j.envpol.2023.121305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Revised: 02/11/2023] [Accepted: 02/14/2023] [Indexed: 06/18/2023]
Abstract
Abandoned brownfields represent a challenge for their recovery. To apply sustainable remediation technologies, such as bioremediation or phytoremediation, indigenous microorganisms are essential agents since they are adapted to the ecology of the soil. Better understanding of microbial communities inhabiting those soils, identification of microorganisms that drive detoxification process and recognising their needs and interactions will significantly improve the outcome of the remediation. With this in mind we have carried out a detailed metagenomic analysis to explore the taxonomic and functional diversity of the prokaryotic and eukaryotic microbial communities in soils, several mineralogically distinct types of pyrometallurgic waste, and groundwater sediments of a former mercury mining and metallurgy site which harbour very high levels of arsenic and mercury pollution. Prokaryotic and eukaryotic communities were identified, which turned out to be more diverse in the surrounding contaminated soils compared to the pyrometallurgic waste. The highest diversity loss was observed in two environments most contaminated with mercury and arsenic (stupp, a solid mercury condenser residue and arsenic-rich soot from arsenic condensers). Interestingly, microbial communities in the stupp were dominated by an overwhelming majority of archaea of the phylum Crenarchaeota, while Ascomycota and Basidiomycota fungi comprised the fungal communities of both stump and soot, results that show the impressive ability of these previously unreported microorganisms to colonize these extreme brownfield environments. Functional predictions for mercury and arsenic resistance/detoxification genes show their increase in environments with higher levels of pollution. Our work establishes the bases to design sustainable remediation methods and, equally important, to study in depth the genetic and functional mechanisms that enable the subsistence of microbial populations in these extremely selective environments.
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Affiliation(s)
- Alexander Prosenkov
- Area of Microbiology, Department of Functional Biology, Environmental Biogeochemistry and Raw Materials Group and IUBA, University of Oviedo, 33006 Oviedo, Asturias, Spain
| | - Christine Cagnon
- Universite de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM, Pau, France
| | - José Luis R Gallego
- INDUROT and Environmental Biogeochemistry and Raw Materials Group, Campus of Mieres, University of Oviedo, 33600 Mieres, Asturias, Spain
| | - Ana Isabel Pelaez
- Area of Microbiology, Department of Functional Biology, Environmental Biogeochemistry and Raw Materials Group and IUBA, University of Oviedo, 33006 Oviedo, Asturias, Spain.
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Thai TD, Lim W, Na D. Synthetic bacteria for the detection and bioremediation of heavy metals. Front Bioeng Biotechnol 2023; 11:1178680. [PMID: 37122866 PMCID: PMC10133563 DOI: 10.3389/fbioe.2023.1178680] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Accepted: 04/04/2023] [Indexed: 05/02/2023] Open
Abstract
Toxic heavy metal accumulation is one of anthropogenic environmental pollutions, which poses risks to human health and ecological systems. Conventional heavy metal remediation approaches rely on expensive chemical and physical processes leading to the formation and release of other toxic waste products. Instead, microbial bioremediation has gained interest as a promising and cost-effective alternative to conventional methods, but the genetic complexity of microorganisms and the lack of appropriate genetic engineering technologies have impeded the development of bioremediating microorganisms. Recently, the emerging synthetic biology opened a new avenue for microbial bioremediation research and development by addressing the challenges and providing novel tools for constructing bacteria with enhanced capabilities: rapid detection and degradation of heavy metals while enhanced tolerance to toxic heavy metals. Moreover, synthetic biology also offers new technologies to meet biosafety regulations since genetically modified microorganisms may disrupt natural ecosystems. In this review, we introduce the use of microorganisms developed based on synthetic biology technologies for the detection and detoxification of heavy metals. Additionally, this review explores the technical strategies developed to overcome the biosafety requirements associated with the use of genetically modified microorganisms.
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Affiliation(s)
| | | | - Dokyun Na
- Department of Biomedical Engineering, Chung-Ang University, Seoul, Republic of Korea
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Sierra MA, Ryon KA, Tierney BT, Foox J, Bhattacharya C, Afshin E, Butler D, Green SJ, Thomas WK, Ramsdell J, Bivens NJ, McGrath K, Mason CE, Tighe SW. Microbiome and metagenomic analysis of Lake Hillier Australia reveals pigment-rich polyextremophiles and wide-ranging metabolic adaptations. ENVIRONMENTAL MICROBIOME 2022; 17:60. [PMID: 36544228 PMCID: PMC9768965 DOI: 10.1186/s40793-022-00455-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Accepted: 12/01/2022] [Indexed: 06/17/2023]
Abstract
Lake Hillier is a hypersaline lake known for its distinctive bright pink color. The cause of this phenomenon in other hypersaline sites has been attributed to halophiles, Dunaliella, and Salinibacter, however, a systematic analysis of the microbial communities, their functional features, and the prevalence of pigment-producing-metabolisms has not been previously studied. Through metagenomic sequencing and culture-based approaches, our results evidence that Lake Hillier is composed of a diverse set of microorganisms including archaea, bacteria, algae, and viruses. Our data indicate that the microbiome in Lake Hillier is composed of multiple pigment-producer microbes, including Dunaliella, Salinibacter, Halobacillus, Psychroflexus, Halorubrum, many of which are cataloged as polyextremophiles. Additionally, we estimated the diversity of metabolic pathways in the lake and determined that many of these are related to pigment production. We reconstructed complete or partial genomes for 21 discrete bacteria (N = 14) and archaea (N = 7), only 2 of which could be taxonomically annotated to previously observed species. Our findings provide the first metagenomic study to decipher the source of the pink color of Australia's Lake Hillier. The study of this pink hypersaline environment is evidence of a microbial consortium of pigment producers, a repertoire of polyextremophiles, a core microbiome and potentially novel species.
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Affiliation(s)
- Maria A Sierra
- Tri-Institutional Computational Biology and Medicine Program, Weill Cornell Medicine, New York, NY, USA
- The HRH Prince Alwaleed Bin Talal Bin Abdulaziz Alsaud Institute for Computational Biomedicine, Weill Cornell Medicine, New York, NY, 10065, USA
| | - Krista A Ryon
- The HRH Prince Alwaleed Bin Talal Bin Abdulaziz Alsaud Institute for Computational Biomedicine, Weill Cornell Medicine, New York, NY, 10065, USA
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, 10065, USA
| | - Braden T Tierney
- The HRH Prince Alwaleed Bin Talal Bin Abdulaziz Alsaud Institute for Computational Biomedicine, Weill Cornell Medicine, New York, NY, 10065, USA
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, 10065, USA
| | - Jonathan Foox
- The HRH Prince Alwaleed Bin Talal Bin Abdulaziz Alsaud Institute for Computational Biomedicine, Weill Cornell Medicine, New York, NY, 10065, USA
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, 10065, USA
| | - Chandrima Bhattacharya
- Tri-Institutional Computational Biology and Medicine Program, Weill Cornell Medicine, New York, NY, USA
- The HRH Prince Alwaleed Bin Talal Bin Abdulaziz Alsaud Institute for Computational Biomedicine, Weill Cornell Medicine, New York, NY, 10065, USA
| | - Evan Afshin
- The HRH Prince Alwaleed Bin Talal Bin Abdulaziz Alsaud Institute for Computational Biomedicine, Weill Cornell Medicine, New York, NY, 10065, USA
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, 10065, USA
| | - Daniel Butler
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, 10065, USA
| | - Stefan J Green
- Genomics and Microbiome Core Facility, Rush University, New York, IL, USA
| | - W Kelley Thomas
- Department of Molecular, Cellular, and Biomedical Sciences, College of Life Sciences and Agriculture, University of New Hampshire, Durham, NH, USA
| | | | - Nathan J Bivens
- DNA Core Facility, University of Missouri, Columbia, MO, USA
| | | | - Christopher E Mason
- The HRH Prince Alwaleed Bin Talal Bin Abdulaziz Alsaud Institute for Computational Biomedicine, Weill Cornell Medicine, New York, NY, 10065, USA.
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, 10065, USA.
- WorldQuant Initiative for Quantitative Prediction, Weill Cornell Medicine, New York, NY, USA.
- The Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY, USA.
| | - Scott W Tighe
- Advanced Genomics Laboratory, University of Vermont Cancer Center, University of Vermont, Burlington, VT, USA.
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Song D, Zhu S, Chen L, Zhang T, Zhang L. The strategy of arsenic metabolism in an arsenic-resistant bacterium Stenotrophomonas maltophilia SCSIOOM isolated from fish gut. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2022; 312:120085. [PMID: 36058313 DOI: 10.1016/j.envpol.2022.120085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Revised: 08/04/2022] [Accepted: 08/29/2022] [Indexed: 06/15/2023]
Abstract
Bacteria are candidates for the biotransformation of environmental arsenic (As), while As metabolism in bacteria is not yet fully understood. In this study, we sequenced the genome of an As-resistant bacterium strain Stenotrophomonas maltophilia SCSIOOM isolated from the fish gut. After arsenate (As(V)) exposure, S. maltophilia transformed As(V) to organoarsenicals, along with the significant change of the expression of 40 genes, including the upregulation of arsH, arsRBC and betIBA. The heterogeneous expression of arsH and arsRBC increased As resistance of E. coli AW3110 by increasing As efflux and transformation. E. coli AW3110 (pET-betIBA) could transform inorganic As into dimethylarsinate (DMA) and nontoxic arsenobetaine (AsB), which suggested that AsB could be synthesized through the synthetic pathway of its analog-glycine betaine. In addition, the existence of arsRBC, betIBA and arsH reduced the reactive oxygen species (ROS) induced by As exposure. In total, these results demonstrated that S. maltophilia adopted an As metabolism strategy by reducing As accumulation and synthesizing less toxic As species. We first reported the production and potential synthetic pathway of AsB in bacteria, which improved our knowledge of As toxicology in microorganisms.
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Affiliation(s)
- Dongdong Song
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Siqi Zhu
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Lizhao Chen
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China; Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou, 511458, China
| | - Ting Zhang
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China; Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou, 511458, China
| | - Li Zhang
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China; Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou, 511458, China; Innovation Academy of South China Sea Ecology and Environmental Engineering, Chinese Academy of Sciences, Guangzhou, 510301, China.
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Bacterial diversity of loggerhead and green turtle eggs from two major nesting beaches from the Turkish coast of the Mediterranean. Arch Microbiol 2022; 204:682. [DOI: 10.1007/s00203-022-03292-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 10/18/2022] [Indexed: 11/05/2022]
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Biological characterization of Bacillus flexus strain SSAI1 transforming highly toxic arsenite to less toxic arsenate mediated by periplasmic arsenite oxidase enzyme encoded by aioAB genes. Biometals 2021; 34:895-907. [PMID: 33956287 DOI: 10.1007/s10534-021-00316-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2021] [Accepted: 04/29/2021] [Indexed: 12/20/2022]
Abstract
Bacillus flexus strain SSAI1 isolated from agro-industry waste, Tuem, Goa, India displayed high arsenite resistance as minimal inhibitory concentration was 25 mM in mineral salts medium. This bacterial strain exposed to 10 mM arsenite demonstrated rapid arsenite oxidation and internalization of 7 mM arsenate within 24 h. The Fourier transformed infrared (FTIR) spectroscopy of cells exposed to arsenite revealed important functional groups on the cell surface interacting with arsenite. Furthermore, scanning electron microscopy combined with electron dispersive X-ray spectroscopy (SEM-EDAX) of cells exposed to arsenite revealed clumping of cells with no surface adsorption of arsenite. Transmission electron microscopy coupled with electron dispersive X-ray spectroscopic (TEM-EDAX) analysis of arsenite exposed cells clearly demonstrated ultra-structural changes and intracellular accumulation of arsenic. Whole-genome sequence analysis of this bacterial strain interestingly revealed the presence of large number of metal(loid) resistance genes, including aioAB genes encoding arsenite oxidase responsible for the oxidation of highly toxic arsenite to less toxic arsenate. Enzyme assay further confirmed that arsenite oxidase is a periplasmic enzyme. The genome of strain SSAI1 also carried glpF, aioS and aioE genes conferring resistance to arsenite. Therefore, multi-metal(loid) resistant arsenite oxidizing Bacillus flexus strain SSAI1 has potential to bioremediate arsenite contaminated environmental sites and is the first report of its kind.
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