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Yan ZX, Li Y, Peng SY, Wei L, Zhang B, Deng XY, Zhong M, Cheng X. Cadmium biosorption and mechanism investigation using two cadmium-tolerant microorganisms isolated from rhizosphere soil of rice. JOURNAL OF HAZARDOUS MATERIALS 2024; 470:134134. [PMID: 38554514 DOI: 10.1016/j.jhazmat.2024.134134] [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: 01/24/2024] [Revised: 03/17/2024] [Accepted: 03/24/2024] [Indexed: 04/01/2024]
Abstract
Microbial remediation of cadmium-contaminated soil offers advantages like environmental friendliness, cost-effectiveness, and simple operation. However, the efficacy of this remediation process relies on obtaining dominant strains and a comprehensive understanding of their Cd adsorption mechanisms. This study identified two Cd-resistant bacteria, Burkholderia sp. 1-22 and Bacillus sp. 6-6, with significant growth-promoting effects from rice rhizosphere soil. The strains showed remarkable Cd resistance up to ∼200 mg/L and alleviated Cd toxicity by regulating pH and facilitating bacterial adsorption of Cd. FTIR analysis showed crucial surface functional groups, like carboxyl and amino groups, on bacteria played significant roles in Cd adsorption. The strains could induce CdCO3 formation via a microbially induced calcium precipitation (MICP) mechanism, confirmed by SEM-EDS, X-ray analysis, and elemental mapping. Pot experiments showed these strains significantly increased organic matter and enzyme activity (e.g., urease, sucrase, peroxidase) in the rhizosphere soil versus the control group. These changes are crucial for restricting Cd mobility. Furthermore, strains 6-6 and 1-22 significantly enhance plant root detoxification of Cd, alleviating toxicity. Notably, increased pH likely plays a vital role in enhancing Cd precipitation and adsorption by strains, converting free Cd into non-bioavailable forms.
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Affiliation(s)
- Zu-Xuan Yan
- Institute of Applied Microbiology, College of Biological Science and Engineering, Jiangxi Agricultural University, Nanchang 330045, China
| | - Yi Li
- Institute of Applied Microbiology, College of Biological Science and Engineering, Jiangxi Agricultural University, Nanchang 330045, China
| | - Shuai-Ying Peng
- Institute of Applied Microbiology, College of Biological Science and Engineering, Jiangxi Agricultural University, Nanchang 330045, China
| | - Lei Wei
- Institute of Applied Microbiology, College of Biological Science and Engineering, Jiangxi Agricultural University, Nanchang 330045, China
| | - Bao Zhang
- Institute of Applied Microbiology, College of Biological Science and Engineering, Jiangxi Agricultural University, Nanchang 330045, China
| | - Xin-Yao Deng
- Institute of Applied Microbiology, College of Biological Science and Engineering, Jiangxi Agricultural University, Nanchang 330045, China
| | - Min Zhong
- Institute of Applied Microbiology, College of Biological Science and Engineering, Jiangxi Agricultural University, Nanchang 330045, China.
| | - Xin Cheng
- Institute of Applied Microbiology, College of Biological Science and Engineering, Jiangxi Agricultural University, Nanchang 330045, China.
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Li T, Du D, Li C, Zhao J, Guo L, Wang X, Zhao J, Xiang W. Investigation on Cr(VI)-bioreduction mechanism and reduction products by a novel Microbacterium sp. strain NEAU-W11. CHEMOSPHERE 2023; 343:140232. [PMID: 37734508 DOI: 10.1016/j.chemosphere.2023.140232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 08/12/2023] [Accepted: 09/18/2023] [Indexed: 09/23/2023]
Abstract
Cr(VI) widely exists in the environment and has highly toxic, carcinogenic and mutagenic effects on all organisms. Physical/chemical methods to remove chromium pollution are economically expensive and have disadvantages like high reagent consumption, energy requirements and so on, while bioremediation is an eco-friendly, simple and cost-effective way. In this study, a novel Cr(VI)-reducing strain, Microbacterium sp. NEAU-W11, was reported, and its reduction mechanism was investigated. Microbacterium sp. NEAU-W11 could effectively degrade Cr(VI) under the conditions of pH 7-10, 15-35 °C, and the coexistence of metal pollutants such as Pb and Ni, etc. In addition, both Fe3+ and Cu2+ could improve the reducing ability of strain NEAU-W11, and glucose and lactose as electron donors also had promoting effect. Heat treatment of resting cells confirmed that chromium removal was not biological sorption but biological reduction. The active reductase of strain NEAU-W11 to chromium(VI) mainly existed in the cell cytoplasm, which is the first report in the genus Microbacterium. Micro-characterization of strain NEAU-W11 and the reduction products identified the reduction products as Cr(III)-ligand complexes bound to extracellular polymeric substances (EPS). Collectively, this study systematically investigated the degradation mechanism of Microbacterium sp. NEAU-W11 and the distribution of degradation product Cr(III), providing a new reduction mechanism for the genus Microbacterium, providing a new perspective for a comprehensive understanding of the degradation and transport of chromium by bacteria, and providing theoretical reference for the migration of metal ions in environmental governance.
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Affiliation(s)
- Tingting Li
- Key Laboratory of Agricultural Microbiology of Heilongjiang Province, Northeast Agricultural University, No. 59 Mucai Street, Xiangfang District, Harbin, 150030, People's Republic of China
| | - Dandan Du
- Key Laboratory of Agricultural Microbiology of Heilongjiang Province, Northeast Agricultural University, No. 59 Mucai Street, Xiangfang District, Harbin, 150030, People's Republic of China
| | - Chenxu Li
- Key Laboratory of Agricultural Microbiology of Heilongjiang Province, Northeast Agricultural University, No. 59 Mucai Street, Xiangfang District, Harbin, 150030, People's Republic of China
| | - Junlei Zhao
- Key Laboratory of Agricultural Microbiology of Heilongjiang Province, Northeast Agricultural University, No. 59 Mucai Street, Xiangfang District, Harbin, 150030, People's Republic of China
| | - Lifeng Guo
- Key Laboratory of Agricultural Microbiology of Heilongjiang Province, Northeast Agricultural University, No. 59 Mucai Street, Xiangfang District, Harbin, 150030, People's Republic of China
| | - Xiangjing Wang
- Key Laboratory of Agricultural Microbiology of Heilongjiang Province, Northeast Agricultural University, No. 59 Mucai Street, Xiangfang District, Harbin, 150030, People's Republic of China
| | - Junwei Zhao
- Key Laboratory of Agricultural Microbiology of Heilongjiang Province, Northeast Agricultural University, No. 59 Mucai Street, Xiangfang District, Harbin, 150030, People's Republic of China.
| | - Wensheng Xiang
- Key Laboratory of Agricultural Microbiology of Heilongjiang Province, Northeast Agricultural University, No. 59 Mucai Street, Xiangfang District, Harbin, 150030, People's Republic of China; State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, People's Republic of China.
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3
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Li D, Wang Y, Qi X, Huang W, Wang Y, Zhao X, Liu Y, Song X, Cao X. A photocatalytic-microbial coupling system for simultaneous removal of harmful algae and enhanced denitrification: Construction, performance and mechanism of action. JOURNAL OF HAZARDOUS MATERIALS 2023; 459:132233. [PMID: 37567143 DOI: 10.1016/j.jhazmat.2023.132233] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Revised: 07/10/2023] [Accepted: 08/04/2023] [Indexed: 08/13/2023]
Abstract
Recently, harmful algal blooms (HABs) have become occurred with increasingly frequency worldwide. High nitrate content is one of the primary causes of eutrophication. Research has shown that photocatalytic materials enhance the effectiveness of microbial denitrification while removing other contaminants, despite some shortcomings. Based on this, we loaded TiO2/C3N4 heterojunctions onto weaveable, flexible carbon fibers and established a novel photocatalytically enhanced microbial denitrification system for the simultaneous removal of harmful algae and Microcystin-LR. We found that 99.35% of Microcystis aeruginosa and 95.34% of MC-LR were simultaneously and effectively removed. Compared to existing denitrification systems, the nitrate removal capacity improved by 72.33%. The denitrifying enzyme activity and electron transport system activity of microorganisms were enhanced by 3.54-3.86 times. Furthermore, the microbial community structure was optimized by the regulation of photogenerated electrons, and the relative abundance of main denitrifying bacteria increased from 50.72% to 66.45%, including Proteobacteria and Bacteroidetes. More importantly, we found that the increased secretion of extracellular polymeric substances by microorganisms may be responsible for the persistence of the reinforcing effect caused by photogenerated electrons in darkness. The higher removal of Microcystis aeruginosa and Microcystin-LR (MC-LR) achieved by the proposed system would reduce the frequency of HAB outbreaks and prevent the associated secondary pollution.
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Affiliation(s)
- Dongpeng Li
- Textile Pollution Controlling Engineering Center of Ministry of Environmental Protection, College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China
| | - Yifei Wang
- Textile Pollution Controlling Engineering Center of Ministry of Environmental Protection, College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China
| | - Xiang Qi
- State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China
| | - Wei Huang
- Textile Pollution Controlling Engineering Center of Ministry of Environmental Protection, College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China
| | - Yuhui Wang
- Textile Pollution Controlling Engineering Center of Ministry of Environmental Protection, College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China
| | - Xiaoxiang Zhao
- Textile Pollution Controlling Engineering Center of Ministry of Environmental Protection, College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China
| | - Yanbiao Liu
- Textile Pollution Controlling Engineering Center of Ministry of Environmental Protection, College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China
| | - Xinshan Song
- Textile Pollution Controlling Engineering Center of Ministry of Environmental Protection, College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China
| | - Xin Cao
- Textile Pollution Controlling Engineering Center of Ministry of Environmental Protection, College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China.
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Zhou F, Yang M, Lu R, Yan C. Simultaneous adsorption-photocatalytic treatment with TiO 2-Sep nanocomposites for in situ remediation of sodium pentachlorophenol contaminated aqueous and soil. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2022; 29:39557-39566. [PMID: 35103948 DOI: 10.1007/s11356-022-18924-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Accepted: 01/24/2022] [Indexed: 06/14/2023]
Abstract
Sodium pentachlorophenol (NaPCP) is a highly toxic and persistent organic pollutant. With sepiolite as the support, a series of TiO2-Sep nanocomposites (NCs) with different Ti/Sep ratios were developed. The objective was to understand the effect of Ti/Sep ratio on the structure and activity of the NCs in aqueous and soil systems and to evaluate the feasibility of the NCs for in situ soil remediation. The prepared NCs were characterized with XRD, SEM, TEM, and N2 adsorption-desorption, respectively. The results showed that high surface area and good dispersion of TiO2 on sepiolite surface were obtained. The photocatalytic activities in aqueous and soil of the as-developed NCs were examined using NaPCP as a model pollutant. Compared with bare sepiolite and TiO2, the heterogeneous NCs showed significantly higher photocatalytic performance in decomposing NaPCP, and the photocatalytic activities varied with the content of TiO2 in the NCs. In aqueous media, treatment with TiO2-S-30 showed excellent degradation efficiency with about 90% NaPCP decomposed in 140 min. Nevertheless, the sample TiO2-S-20 promotes maximum rate reduction of NaPCP with above 90% within 20-h irradiation in soil. The results indicate that an appropriate Ti/Sep ratio could significantly enhance the activities of NCs on NaPCP remediation and the role of carrier sepiolite is more important in soil media than that in aqueous phase. The excellent performance of the TiO2-Sep in wastewater degradation and soil remediation can be attributed to the synergistic effects between the high photocatalytic activity of TiO2 nanoparticles and the strong adsorption capacity of sepiolite nanofibers. This work revealed that sepiolite adsorption coupled with TiO2 photocatalysis can be one promising technique for in situ remediation of NaPCP-contaminated soil.
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Affiliation(s)
- Feng Zhou
- Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan, 430074, China
| | - Minghui Yang
- Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan, 430074, China
| | - Ronghong Lu
- Li'Jiang LONGi Silicon Materials Corp, Lijiang, 674800, China
| | - Chunjie Yan
- Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan, 430074, China.
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5
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Zhou X, Xiong W, Li Y, Zhang C, Xiong X. A novel simultaneous coupling of memory photocatalysts and microbial communities for alternate removal of dimethyl phthalate and nitrate in water under light/dark cycles. JOURNAL OF HAZARDOUS MATERIALS 2022; 430:128395. [PMID: 35149509 DOI: 10.1016/j.jhazmat.2022.128395] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2021] [Revised: 01/26/2022] [Accepted: 01/28/2022] [Indexed: 06/14/2023]
Abstract
Efficient and sustainable removal of both organic and inorganic pollutants from contaminated water is an important but difficult task. Here, a novel chemical-biological coupling concept, namely simultaneous coupling of memory photocatalysts and microbial communities (SCMPMC), is proposed for the first time that alternates the removal of organic and inorganic pollutants under successive light/dark cycles. We established this novel coupling system with WO3/g-C3N4 memory photocatalysts and river sediment microbial communities, and applied it to alternately remove dimethyl phthalate (DMP) and nitrate under light/dark cycles. The performance of SCMPMC under the light/dark cycles (12/12 h) showed that ~84.90% of the DMP was removed mainly via robust photocatalytic oxidation during the light phase, and ~86.80% of the nitrate was removed via microbial reduction enhanced by photogenerated electrons stored in the WO3/g-C3N4 memory photocatalysts during the dark phase within one cycle. The microbial communities were positively affected by adding WO3/g-C3N4, as evidenced by increased enzyme activities, cellular antigen metabolism, and relative abundance of typical denitrifiers, including Proteobacteria and Bacteroidetes. These results will contribute to the development of promising decontamination methods and mechanisms to control water pollution driven by the natural day/night cycle.
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Affiliation(s)
- Xinyi Zhou
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of Education, College of Environment, Hohai University, Nanjing 210098, PR China
| | - Wei Xiong
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of Education, College of Environment, Hohai University, Nanjing 210098, PR China
| | - Yi Li
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of Education, College of Environment, Hohai University, Nanjing 210098, PR China.
| | - Chi Zhang
- College of Mechanics and Materials, Hohai University, Xikang Road #1, Nanjing 210098, PR China
| | - Xinyan Xiong
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of Education, College of Environment, Hohai University, Nanjing 210098, PR China
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6
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Zhang H, Lu Y, Li Y, Wang C, Yu Y, Zhang W, Wang L, Niu L, Zhang C. Propelling the practical application of the intimate coupling of photocatalysis and biodegradation system: System amelioration, environmental influences and analytical strategies. CHEMOSPHERE 2022; 287:132196. [PMID: 34517239 DOI: 10.1016/j.chemosphere.2021.132196] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 09/04/2021] [Accepted: 09/06/2021] [Indexed: 06/13/2023]
Abstract
The intimate coupling of photocatalysis and biodegradation (ICPB) possesses an enhanced ability of recalcitrant contaminant removal and energy generation, owing to the compact communication between biotic components and photocatalysts during the system operation. The photocatalysts in the ICPB system could dispose of noxious contaminants to relieve the external pressure on microorganisms which could realize the mineralization of the photocatalytic degradation products. However, due to the complex components in the composite system, the mechanism of the ICPB system has not been completely understood. Moreover, the variable environmental conditions would play a significant role in the ICPB system performance. The further development of the ICPB scheme requires clarification on how to reach an accurate understanding of the system condition during the practical application. This review starts by offering detailed information on the system construction and recent progress in the system components' amelioration. We then describe the potential influences of relevant environmental factors on the system performance, and the analytical strategies applicable for comprehending the critical processes during the system operation are further summarized. Finally, we put forward the research gaps in the current system and envision the system's prospective application. This review provides a valuable reference for future researches that are devoted to assessing the environmental disturbance and exploring the reaction mechanisms during the practical application of the ICPB system.
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Affiliation(s)
- Huanjun Zhang
- Key Laboratory of Integrated Regulation and Resource Development of Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Xikang Road #1, Nanjing, 210098, PR China
| | - Yin Lu
- Key Laboratory of Integrated Regulation and Resource Development of Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Xikang Road #1, Nanjing, 210098, PR China
| | - Yi Li
- Key Laboratory of Integrated Regulation and Resource Development of Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Xikang Road #1, Nanjing, 210098, PR China.
| | - Chao Wang
- School of Environmental Science and Engineering, Southern University of Science and Technology, Xueyuan Road #1088, Shenzhen, 518055, PR China.
| | - Yanan Yu
- Key Laboratory of Integrated Regulation and Resource Development of Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Xikang Road #1, Nanjing, 210098, PR China
| | - Wenlong Zhang
- Key Laboratory of Integrated Regulation and Resource Development of Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Xikang Road #1, Nanjing, 210098, PR China
| | - Longfei Wang
- Key Laboratory of Integrated Regulation and Resource Development of Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Xikang Road #1, Nanjing, 210098, PR China
| | - Lihua Niu
- Key Laboratory of Integrated Regulation and Resource Development of Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Xikang Road #1, Nanjing, 210098, PR China
| | - Chi Zhang
- Key Laboratory of Integrated Regulation and Resource Development of Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Xikang Road #1, Nanjing, 210098, PR China
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Peng D, Qiao S, Luo Y, Ma H, Zhang L, Hou S, Wu B, Xu H. Performance of microbial induced carbonate precipitation for immobilizing Cd in water and soil. JOURNAL OF HAZARDOUS MATERIALS 2020; 400:123116. [PMID: 32569980 DOI: 10.1016/j.jhazmat.2020.123116] [Citation(s) in RCA: 71] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 04/23/2020] [Accepted: 06/01/2020] [Indexed: 06/11/2023]
Abstract
Microbial induced carbonate precipitation (MICP) is known as a significant process for remediating heavy metals contaminated environment. In this study, a novel Cd-resistant ureolytic bacteria was isolated and identified as Enterobacter sp. Its performances for immobilizing Cd in solution and soil were systematically discussed at different treatment conditions. Results showed that initial pH and Cd concentration were important parameters to influence Cd removal rate. The maximal Cd removal rate in solution reached 99.50 % within 7 days by MICP. The precipitation produced in Cd removal process were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectrometer to understand the removal mechanism. Analyses showed that Cd removal mechanism of CJW-1 was predominately via biominerals including calcites and vaterites to absorb Cd2+. Cd immobilization tests demonstrated that the highest Cd-immobilization rate in soil could reach 56.10 %. Although all treatments contribute to soil pH, fertility, and enzyme activities improvement, oyster shell wastes (OS) had a better effect on soil cation exchange capacity. All treatments had negative effects on soil respiration and bacterial community, but OS can alleviate such adverse influence. Our results emphasized that Cd-resistant ureolytic bacteria strain CJW-1 combined with OS had excellent ability and reuse value to remediate Cd-contaminated environment.
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Affiliation(s)
- Dinghua Peng
- Key Laboratory of Bio-Resource and Eco-Evironment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu 610065, PR China
| | - Suyu Qiao
- Key Laboratory of Bio-Resource and Eco-Evironment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu 610065, PR China
| | - Yao Luo
- Key Laboratory of Bio-Resource and Eco-Evironment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu 610065, PR China
| | - Hang Ma
- Key Laboratory of Bio-Resource and Eco-Evironment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu 610065, PR China
| | - Lei Zhang
- Key Laboratory of Bio-Resource and Eco-Evironment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu 610065, PR China
| | - Siyu Hou
- Key Laboratory of Bio-Resource and Eco-Evironment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu 610065, PR China
| | - Bin Wu
- Key Laboratory of Bio-Resource and Eco-Evironment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu 610065, PR China
| | - Heng Xu
- Key Laboratory of Bio-Resource and Eco-Evironment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu 610065, PR China.
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He X, Xu M, Wei Q, Tang M, Guan L, Lou L, Xu X, Hu Z, Chen Y, Shen Z, Xia Y. Promotion of growth and phytoextraction of cadmium and lead in Solanum nigrum L. mediated by plant-growth-promoting rhizobacteria. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2020; 205:111333. [PMID: 32979802 DOI: 10.1016/j.ecoenv.2020.111333] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 08/15/2020] [Accepted: 09/10/2020] [Indexed: 05/27/2023]
Abstract
Plant growth-promoting rhizobacteria (PGPR) are a specific category of microbes that improve plant growth and promote greater tolerance to metal stress through their interactions with plant roots. We evaluated the effects of phytoremediation combining the cadmium accumulator Solanum nigrum L. and two Cd- and Pb-resistant bacteria isolates. To understand the interaction between PGPR and their host plant, we conducted greenhouse experiments with inoculation treatments at Nanjing Agricultural University (Jiangsu Province, China), in June 2018. Two Cd- and Pb-resistant PGPR with various growth-promoting properties were isolated from heavy metal-contaminated soil. 16S rRNA analyses indicated that the two isolates were Bacillus genus, and they were named QX8 and QX13. Pot experiments demonstrated that inoculation may improve the rhizosphere soil environment and promote absorption of Fe and P by plants. Inoculation with QX8 and QX13 also enhanced the dry weight of shoots (1.36- and 1.7-fold, respectively) and roots (1.42- and 1.96-fold) of plants growing in Cd- and Pb-contaminated soil, and significantly increased total Cd (1.28-1.81 fold) and Pb (1.08-1.55 fold) content in aerial organs, compared to non-inoculated controls. We also detected increases of 23% and 22% in the acid phosphatase activity of rhizosphere soils inoculated with QX8 and QX13, respectively. However, we did not detect significant differences between inoculated and non-inoculated treatments in Cd and Pb concentrations in plants and available Cd and Pb content in rhizosphere soils. We demonstrated that PGPR-assisted phytoremediation is a promising technique for remediating heavy metal-contaminated soils, with the potential to enhance phytoremediation efficiency and improve soil quality.
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Affiliation(s)
- Xiaoman He
- College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, China
| | - Mingjing Xu
- College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, China
| | - Qingpeng Wei
- College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, China
| | - Mingyu Tang
- College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, China
| | - Likang Guan
- College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, China
| | - Laiqing Lou
- College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, China
| | - Xiaoming Xu
- College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, China
| | - Zhubing Hu
- Institute of Plant Stress Biology, State Key Laboratory of Cotton Biology, Department of Biology, Henan University, Kaifeng, 475001, China
| | - Yahua Chen
- College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, China; Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource, Nanjing, 210095, China
| | - Zhenguo Shen
- College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, China; Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource, Nanjing, 210095, China
| | - Yan Xia
- College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, China; Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource, Nanjing, 210095, China.
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9
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Yao Y, Hu L, Li S, Zeng Q, Zhong H, He Z. Exploration on the bioreduction mechanisms of Cr(VI) and Hg(II) by a newly isolated bacterial strain Pseudomonas umsongensis CY-1. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2020; 201:110850. [PMID: 32531571 DOI: 10.1016/j.ecoenv.2020.110850] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 05/24/2020] [Accepted: 06/01/2020] [Indexed: 06/11/2023]
Abstract
Despite of significant progress in remediation of Cr(VI) or Hg(II) pollution by microorganisms, study on the reduction of both Cr(VI) and Hg(II) by the same microbial strain was not reported so far, which is actually important for bioremediation of contaminated sites with multiple heavy metals. In this study, Pseudomonas umsongensis CY-1 was newly isolated from chromium-contaminated soil and showed remediation potentials for both Cr(VI) and Hg(II) pollution. The highest Cr(VI) (93.9%) and Hg(II) (82.8%) reduction rates were obtained at the initial concentration of 5 mg/L. Comparison between removal by resting cells and heat-treated resting cells demonstrated that P. umsongensis CY-1 removed Cr(VI) and Hg(II) from Tris-HCl buffer (pH 7.0) mainly through reduction instead of adsorption. By comparing the Cr(VI) and Hg(II) reduction rates of different cellular fractions, it was found that Cr(VI) and Hg(II) reductions mainly happened in the cytoplasm of P. umsongensis CY-1, which were further demonstrated by Transmission electron microscopy (TEM) analysis. Furthermore, analysis of X-ray photoelectron spectroscopy demonstrated that the reduction products of Cr(VI) and Hg(II) were mainly in the form of Cr(III) and Hg (0), respectively. The findings in this study will provide a guide for further insights in the bioremediation of contaminated sites with multiple heavy metals.
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Affiliation(s)
- Yang Yao
- School of Minerals Processing and Bioengineering, Key Laboratory of Biohydrometallurgy of Ministry of Education, Central South University, Changsha, 410083, China
| | - Liang Hu
- School of Minerals Processing and Bioengineering, Key Laboratory of Biohydrometallurgy of Ministry of Education, Central South University, Changsha, 410083, China
| | - Shuzhen Li
- School of Minerals Processing and Bioengineering, Key Laboratory of Biohydrometallurgy of Ministry of Education, Central South University, Changsha, 410083, China
| | - Qiang Zeng
- School of Minerals Processing and Bioengineering, Key Laboratory of Biohydrometallurgy of Ministry of Education, Central South University, Changsha, 410083, China
| | - Hui Zhong
- School of Life Science, Central South University, Changsha, 410012, China.
| | - Zhiguo He
- School of Minerals Processing and Bioengineering, Key Laboratory of Biohydrometallurgy of Ministry of Education, Central South University, Changsha, 410083, China; Faculty of Materials Metallurgy & Chemistry, Jiangxi University of Science & Technology, Ganzhou, Jiangxi, 341000, China.
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10
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Zahra Z, Habib Z, Chung S, Badshah MA. Exposure Route of TiO 2 NPs from Industrial Applications to Wastewater Treatment and Their Impacts on the Agro-Environment. NANOMATERIALS (BASEL, SWITZERLAND) 2020; 10:E1469. [PMID: 32727126 PMCID: PMC7466468 DOI: 10.3390/nano10081469] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 07/20/2020] [Accepted: 07/20/2020] [Indexed: 02/07/2023]
Abstract
The tremendous increase in the production and consumption of titanium dioxide (TiO2) nanoparticles (NPs) in numerous industrial products and applications has augmented the need to understand their role in wastewater treatment technologies. Likewise, the deleterious effects of wastewater on the environment and natural resources have compelled researchers to find out most suitable, economical and environment friendly approaches for its treatment. In this context, the use of TiO2 NPs as the representative of photocatalytic technology for industrial wastewater treatment is coming to the horizon. For centuries, the use of industrial wastewater to feed agriculture land has been a common practice across the globe and the sewage sludge generated from wastewater treatment plants is also used as fertilizer in agricultural soils. Therefore, it is necessary to be aware of possible exposure pathways of these NPs, especially in the perspective of wastewater treatment and their impacts on the agro-environment. This review highlights the potential exposure route of TiO2 NPs from industrial applications to wastewater treatment and its impacts on the agro-environment. Key elements of the review present the recent developments of TiO2 NPs in two main sectors including wastewater treatment and the agro-environment along with their potential exposure pathways. Furthermore, the direct exposure routes of these NPs from production to end-user consumption until their end phase needs to be studied in detail and optimization of their suitable applications and controlled use to ensure environmental safety.
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Affiliation(s)
- Zahra Zahra
- Department of Civil & Environmental Engineering, University of California-Irvine, Irvine, CA 92697, USA
| | - Zunaira Habib
- Institute of Environmental Sciences and Engineering, School of Civil and Environmental Engineering, National University of Sciences and Technology, Islamabad 44000, Pakistan;
| | - Sujin Chung
- Plamica Labs, Batten Hall, 125 Western Ave, Allston, MA 02163, USA;
| | - Mohsin Ali Badshah
- Department of Chemical and Biomolecular Engineering, University of California-Irvine, Irvine, CA 92697, USA;
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11
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Hao M, Wang J, Zhao J, Liu N, Feng C, Wang Z, Sun D, Hu Q, Wang Z, Wang F, Yang J, Lu L, Dong W, Duan L, Liu Z, Liu J. Biological Visual Detection for Advanced Photocatalytic Oxidation toward Pesticide Detoxification. ACS OMEGA 2019; 4:19655-19663. [PMID: 31788596 PMCID: PMC6881827 DOI: 10.1021/acsomega.9b02289] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 11/04/2019] [Indexed: 05/29/2023]
Abstract
Photocatalytic oxidation treatment is an emerging and fast developed eco-friendly, energy-saving, and efficient advanced oxidation technology for degrading hazardous pesticides. The conventional chemical detection to evaluate the effects for this process depends on the broken chemical structure, only giving residual content and product chemical composition. However, it misses direct visual detection on the toxicity and the quantitative analysis of pesticide detoxification. Here, we develop a novel strategy to combine photocatalytic oxidation with a zebrafish biological model to provide a direct visual detection on the environmental detoxification. The mortality or deformity of zebrafish embryos (ZEs) acts as an indicator. Over the irradiation duration threshold, the mortality of ZEs decreases to 23.3% for pure chlorothalonil (CTL-P) after photocatalytic oxidation treatment for 1 h, and the deformity reduces to 13.3% for commercial CTL (CTL-C) after 30 min and to 3.33% for tetramethylthiuram disulfide (TMTD) after 20 min. The toxicity of CTL-C and TMTD could be completely removed by photocatalytic oxidation treatment and causes no damage to the ZE developmental morphology. Chemical analyses demonstrate the degradation of CTL into inorganic compounds and TMTD into small organic molecules. Among these highlighted heterogeneous photocatalysts (g-C3N4, BiVO4, Ag3PO4, and P25), g-C3N4 exhibits the highest photocatalytic detoxification for CTL-P, CTL-C, and TMTD.
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Affiliation(s)
- Mingjiao Hao
- Inner
Mongolia Key Lab of Carbon Nanomaterials, Nano Innovation Institute
(NII), College of Chemistry and Chemical Engineering, Inner Mongolia University for Nationalities (IMUN), Tongliao, Inner Mongolia 028000, P. R. China
| | - Jinghui Wang
- Inner
Mongolia Key Lab of Carbon Nanomaterials, Nano Innovation Institute
(NII), College of Chemistry and Chemical Engineering, Inner Mongolia University for Nationalities (IMUN), Tongliao, Inner Mongolia 028000, P. R. China
| | - Jiadi Zhao
- Inner
Mongolia Key Lab of Carbon Nanomaterials, Nano Innovation Institute
(NII), College of Chemistry and Chemical Engineering, Inner Mongolia University for Nationalities (IMUN), Tongliao, Inner Mongolia 028000, P. R. China
| | - Nan Liu
- The
Quality&Safety Center of Agricultural and Animal Products Ministry
of Tongliao, Tongliao, Inner Mongolia 028000, P. R. China
| | - Chi Feng
- Inner
Mongolia Key Laboratory of Toxicant Monitoring and Toxicology, Collage
of Animal Science and Technology, Inner
Mongolia University for Nationalities, Tongliao, Inner Mongolia 028000, P. R. China
| | - Ziping Wang
- Inner
Mongolia Key Lab of Carbon Nanomaterials, Nano Innovation Institute
(NII), College of Chemistry and Chemical Engineering, Inner Mongolia University for Nationalities (IMUN), Tongliao, Inner Mongolia 028000, P. R. China
| | - Danhui Sun
- Inner
Mongolia Key Lab of Carbon Nanomaterials, Nano Innovation Institute
(NII), College of Chemistry and Chemical Engineering, Inner Mongolia University for Nationalities (IMUN), Tongliao, Inner Mongolia 028000, P. R. China
| | - Quanli Hu
- Inner
Mongolia Key Lab of Carbon Nanomaterials, Nano Innovation Institute
(NII), College of Chemistry and Chemical Engineering, Inner Mongolia University for Nationalities (IMUN), Tongliao, Inner Mongolia 028000, P. R. China
| | - Zhiyu Wang
- Inner
Mongolia Key Lab of Carbon Nanomaterials, Nano Innovation Institute
(NII), College of Chemistry and Chemical Engineering, Inner Mongolia University for Nationalities (IMUN), Tongliao, Inner Mongolia 028000, P. R. China
| | - Feng Wang
- Inner
Mongolia Key Laboratory of Toxicant Monitoring and Toxicology, Collage
of Animal Science and Technology, Inner
Mongolia University for Nationalities, Tongliao, Inner Mongolia 028000, P. R. China
| | - Jingfeng Yang
- Inner
Mongolia Key Laboratory of Toxicant Monitoring and Toxicology, Collage
of Animal Science and Technology, Inner
Mongolia University for Nationalities, Tongliao, Inner Mongolia 028000, P. R. China
| | - Luhua Lu
- Faculty
of Materials Science and Chemistry, China
University of Geosciences Wuhan, 388 Lumo Road, Wuhan 430074, Hubei, P. R. China
| | - Wu Dong
- Inner
Mongolia Key Laboratory of Toxicant Monitoring and Toxicology, Collage
of Animal Science and Technology, Inner
Mongolia University for Nationalities, Tongliao, Inner Mongolia 028000, P. R. China
| | - Limei Duan
- Inner
Mongolia Key Lab of Carbon Nanomaterials, Nano Innovation Institute
(NII), College of Chemistry and Chemical Engineering, Inner Mongolia University for Nationalities (IMUN), Tongliao, Inner Mongolia 028000, P. R. China
| | - Zhengang Liu
- Research
Center for Eco-Environmental Sciences, Chinese
Academy of Sciences, 18 Shuangqing Road, Beijing, Beijing 100085, P.
R. China
| | - Jinghai Liu
- Inner
Mongolia Key Lab of Carbon Nanomaterials, Nano Innovation Institute
(NII), College of Chemistry and Chemical Engineering, Inner Mongolia University for Nationalities (IMUN), Tongliao, Inner Mongolia 028000, P. R. China
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12
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Zhang Q, Liu H, Saleem M, Wang C. Biotransformation of chlorothalonil by strain Stenotrophomonas acidaminiphila BJ1 isolated from farmland soil. ROYAL SOCIETY OPEN SCIENCE 2019; 6:190562. [PMID: 31827822 PMCID: PMC6894561 DOI: 10.1098/rsos.190562] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2019] [Accepted: 10/03/2019] [Indexed: 06/10/2023]
Abstract
Chlorothalonil is a widely used fungicide, but the contamination of soil and water environments by this chemical causes potential threats to biodiversity. Given the metabolic potential of soil microorganisms, there is a need for developing microbiological approaches to degrade persistent compounds, such as chlorothalonil, in contaminated sites. Here in this study, we isolated a bacterial strain (namely, BJ1) capable of degrading chlorothalonil from a chlorothalonil-contaminated farmland soil in the Shandong Province, China. Using 16S rDNA gene sequencing, morphological and biological characteristics, we identified the strain BJ1 as Stenotrophomonas acidaminiphila. The strain BJ1 uses chlorothalonil as a sole carbon source. At initial concentrations of 50, 100, 200 and 300 mg l-1, it degraded 91.5%, 89.4%, 86.5% and 83.5% of chlorothalonil after 96 h of inoculation under optimum conditions (30°C and pH 7.0). Two metabolites, methyl-2,5,6-trichloro-3-cyano-4-methoxy-benzoate and methyl-3-cyano-2,4,5,6-tetrachlorobenzoate, were detected and identified based on HPLC-MS analysis, which suggests that the strain BJ1 metabolized chlorothalonil through the hydroxylation of chloro-group and hydration of cyano-group. The results of this study highlight the great potential for this bacterium to be used in chlorothalonil pollution remediation.
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Affiliation(s)
- Qingming Zhang
- Key Lab of Integrated Crop Pest Management of Shandong Province, College of Plant Health and Medicine, Qingdao Agricultural University, Qingdao 266109, People's Republic of China
| | - Hongyu Liu
- Key Lab of Integrated Crop Pest Management of Shandong Province, College of Plant Health and Medicine, Qingdao Agricultural University, Qingdao 266109, People's Republic of China
| | - Muhammad Saleem
- Department of Biological Sciences, Alabama State University, Montgomery, AL 36101, USA
| | - Caixia Wang
- Key Lab of Integrated Crop Pest Management of Shandong Province, College of Plant Health and Medicine, Qingdao Agricultural University, Qingdao 266109, People's Republic of China
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13
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Wu M, Li Y, Li J, Wang Y, Xu H, Zhao Y. Bioreduction of hexavalent chromium using a novel strain CRB-7 immobilized on multiple materials. JOURNAL OF HAZARDOUS MATERIALS 2019; 368:412-420. [PMID: 30703702 DOI: 10.1016/j.jhazmat.2019.01.059] [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: 10/24/2018] [Revised: 01/17/2019] [Accepted: 01/18/2019] [Indexed: 06/09/2023]
Abstract
In this study, a novel Cr(VI) tolerant strain CRB-7 identified as Bacillus sp., was isolated and characterized for its high Cr(VI) reduction. The strain CRB-7 grew well and effectively reduced Cr(VI) under various conditions including pH (7-9), temperature (30-40 °C) and Cr(VI) concentrations (50-250 mg L-1). It almost completely reduced 120 mg L-1 Cr(VI) within 48 h under optimized condition of pH 7 and 37 °C. Further characterization by SEM-EDS and FTIR analyses indicated Cr(VI) removal mechanism of CRB-7 was predominately via bioreduction with little amount of bioadsorption. Furthermore, the strain CRB-7 based immobilized biobeads were successfully synthesized using five different porous materials as bacterial loading carrier respectively to ascertain the optimal immobilization biocomposite for Cr(VI) removal. CRB-7 cells immobilized with 3% sodium alginate (SA) and 5% humic acid (HA) exhibited the highest Cr(VI) removal efficiency. Moreover, immobilized biobeads have the advantages over free cells in being more stable and easier to reuse. High Cr(VI) reducing ability of the free and immobilized CRB-7 cells suggest the strain CRB-7, especially the B-HA-SA biocomposite is promising for remediating Cr(VI)-contaminated sites.
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Affiliation(s)
- Minghui Wu
- Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610064, Sichuan, China
| | - Yunzhen Li
- Sichuan Academy of Environmental Sciences, Chengdu, Sichuan, 610041, China
| | - Junjie Li
- Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610064, Sichuan, China
| | - Ying Wang
- Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610064, Sichuan, China
| | - Heng Xu
- Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610064, Sichuan, China.
| | - Yun Zhao
- Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610064, Sichuan, China.
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14
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Larue C, Baratange C, Vantelon D, Khodja H, Surblé S, Elger A, Carrière M. Influence of soil type on TiO 2 nanoparticle fate in an agro-ecosystem. THE SCIENCE OF THE TOTAL ENVIRONMENT 2018; 630:609-617. [PMID: 29494970 DOI: 10.1016/j.scitotenv.2018.02.264] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Revised: 02/21/2018] [Accepted: 02/21/2018] [Indexed: 06/08/2023]
Abstract
Nanoparticles (NPs) and in particular TiO2-NPs are increasingly included in commercial goods leading to their accumulation in sewage sludge which is spread on agricultural soils as fertilizers in many countries. Crop plants are thus a very likely point of entry for NPs in the food chain up to humans. So far, soil influence on NP fate has been under-investigated. In this article, we studied the partitioning of TiO2-NPs between soil and soil leachate, their uptake and biotransformation in wheat seedlings and their impact on plant development after exposure on 4 different types of soil with different characteristics: soil texture (from sandy to clayey), soil pH, cationic exchange capacity, organic matter content. Results suggest that a NP contamination occurring on agricultural soils will mainly lead to NP accumulation in soil (increase of Ti concentration up to 302% in sand) but to low to negligible transfer to soil leachate and plant shoot. In our experimental conditions, no sign of acute phytotoxicity has been detected (growth, biomass, chlorophyll content). Clay content above 6% together with organic matter content above 1.5% lead to translocation factor from soil to plant leaves below 2.5% (i.e. below 13mgTi·kg-1 dry leaves). Taken together, our results suggest low risk of crop contamination in an agro-ecosystem.
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Affiliation(s)
- C Larue
- ECOLAB, Université de Toulouse, CNRS, Toulouse, France.
| | - C Baratange
- ECOLAB, Université de Toulouse, CNRS, Toulouse, France
| | - D Vantelon
- Synchrotron SOLEIL, L'Orme des Merisiers 48, St Aubin, 91192 Gif-sur-Yvette Cedex, France.
| | - H Khodja
- LEEL, NIMBE, CEA/CNRS, Université Paris Saclay, 91191, Gif sur Yvette, France.
| | - S Surblé
- LEEL, NIMBE, CEA/CNRS, Université Paris Saclay, 91191, Gif sur Yvette, France.
| | - A Elger
- ECOLAB, Université de Toulouse, CNRS, Toulouse, France.
| | - M Carrière
- Univ. Grenoble Alpes, INAC, SyMMES, Chimie Interface Biologie pour l'Environnement, la Santé et la Toxicologie (CIBEST), F-38000, Grenoble, France.
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15
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Zhang Q, Saleem M, Wang C. Probiotic strain Stenotrophomonas acidaminiphila BJ1 degrades and reduces chlorothalonil toxicity to soil enzymes, microbial communities and plant roots. AMB Express 2017; 7:227. [PMID: 29275520 PMCID: PMC5742092 DOI: 10.1186/s13568-017-0530-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Accepted: 12/19/2017] [Indexed: 11/10/2022] Open
Abstract
Chlorothalonil, a non-systemic and broad-spectrum fungicide, is widely used to control the pathogens of agricultural plants. Although microbial degradation of chlorothalonil is known, we know little about the colonization and degradation capacity of these microbes in the natural and semi-natural soil environments. Therefore, we studied the colonization and detoxification potential of a chlorothalonil degrading Stenotrophomonas acidaminiphila probiotic strain BJ1 in the soil under green conditions. The results from polymerase chain reaction-denaturing gradient gel electrophoresis demonstrated that probiotic strain BJ1 successfully colonized the soil by competing with the native biota. Moreover, the bacterial inoculation stimulated some members of indigenous soil microbial communities. Meantime, the degradation half-life of chlorothalonil decreased from 9.0 to 4.9 days in the soil environment. Moreover, the results from enzymatic activities and micronucleus test of Vicia faba root tips showed that the probiotic strain BJ1 reduced the ecotoxicity and genotoxicity of chlorothalonil in the soil. We suggest that probiotic strains like BJ1 could potentially alleviate the toxic effects of pesticides on soil microbes and plant roots under greenhouse conditions.
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