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Wang HM, Hu GR, Luo WY, Li FL. The horizontal gene transfer of perchlorate reduction genomic island in three bacteria from an ecological niche. Appl Microbiol Biotechnol 2024; 108:22. [PMID: 38159121 DOI: 10.1007/s00253-023-12827-3] [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: 03/05/2023] [Revised: 09/25/2023] [Accepted: 11/01/2023] [Indexed: 01/03/2024]
Abstract
Three new strains of dissimilatory perchlorate-reducing bacteria (DPRB), QD19-16, QD1-5, and P3-1, were isolated from an active sludge. Phylogenetic trees based on 16S rRNA genes indicated that QD19-16, QD1-5, and P3-1 belonged to Brucella, Acidovorax, and Citrobacter, respectively, expanding the distribution of DPRB in the Proteobacteria. The three strains were gram-negative and facultative anaerobes with rod-shaped cells without flagella, which were 1.0-1.6 μm long and 0.5-0.6 μm wide. The three DPRB strains utilized similar broad spectrum of electron donors and acceptors and demonstrated a similar capability to reduce perchlorate within 6 days. The enzyme activity of perchlorate reductase in QD19-16 toward chlorate was higher than that toward perchlorate. The high sequence similarity of the perchlorate reductase operon and chlorite dismutase genes in the perchlorate reduction genomic islands (PRI) of the three strains implied that they were monophyletic origin from a common ancestral PRI. Two transposase genes (tnp1 and tnp2) were found in the PRIs of strain QD19-16 and QD1-5, but were absent in the strain P3-1 PRI. The presence of fragments of IR sequences in the P3-1 PRI suggested that P3-1 PRI had previously contained these two tnp genes. Therefore, it is plausible to suggest that a common ancestral PRI transferred across the strains Brucella sp. QD19-16, Acidovorax sp. QD1-5, and Citrobacter sp. P3-1 through horizontal gene transfer, facilitated by transposases. These results provided a direct evidence of horizontal gene transfer of PRI that could jump across phylogenetically unrelated bacteria through transposase. KEY POINTS: • Three new DPRB strains can effectively remove high concentration of perchlorate. • The PRIs of three DPRB strains are acquired from a single ancestral PRI. • PRIs are incorporated into different bacteria genome through HGT by transposase.
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Affiliation(s)
- Hao-Ming Wang
- Shandong Provincial Key Laboratory of Synthetic Biology, Qingdao C1 Refinery Engineering Research CenterQingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, China
- Shandong Energy Institute, Qingdao, 266101, China
- Qingdao New Energy Shandong Laboratory, Qingdao, 266101, China
| | - Guang-Rong Hu
- Shandong Provincial Key Laboratory of Synthetic Biology, Qingdao C1 Refinery Engineering Research CenterQingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, China
- Shandong Energy Institute, Qingdao, 266101, China
- Qingdao New Energy Shandong Laboratory, Qingdao, 266101, China
| | - Wen-Yong Luo
- Shandong Provincial Key Laboratory of Synthetic Biology, Qingdao C1 Refinery Engineering Research CenterQingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, China
- School of Environmental and Municipal Engineering, Qingdao University of Technology, Qingdao, 266400, China
| | - Fu-Li Li
- Shandong Provincial Key Laboratory of Synthetic Biology, Qingdao C1 Refinery Engineering Research CenterQingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, China.
- Shandong Energy Institute, Qingdao, 266101, China.
- Qingdao New Energy Shandong Laboratory, Qingdao, 266101, China.
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Riedel R, Commichau FM, Benndorf D, Hertel R, Holzer K, Hoelzle LE, Mardoukhi MSY, Noack LE, Martienssen M. Biodegradation of selected aminophosphonates by the bacterial isolate Ochrobactrum sp. BTU1. Microbiol Res 2024; 280:127600. [PMID: 38211497 DOI: 10.1016/j.micres.2024.127600] [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: 09/04/2023] [Revised: 12/19/2023] [Accepted: 01/02/2024] [Indexed: 01/13/2024]
Abstract
Aminophosphonates, like glyphosate (GS) or metal chelators such as ethylenediaminetetra(methylenephosphonic acid) (EDTMP), are released on a large scale worldwide. Here, we have characterized a bacterial strain capable of degrading synthetic aminophosphonates. The strain was isolated from LC/MS standard solution. Genome sequencing indicated that the strain belongs to the genus Ochrobactrum. Whole-genome classification using pyANI software to compute a pairwise ANI and other metrics between Brucella assemblies and Ochrobactrum contigs revealed that the bacterial strain is designated as Ochrobactrum sp. BTU1. Degradation batch tests with Ochrobactrum sp. BTU1 and the selected aminophosphonates GS, EDTMP, aminomethylphosphonic acid (AMPA), iminodi(methylene-phosphonic) (IDMP) and ethylaminobis(methylenephosphonic) acid (EABMP) showed that the strain can use all phosphonates as sole phosphorus source during phosphorus starvation. The highest growth rate was achieved with AMPA, while EDTMP and GS were least supportive for growth. Proteome analysis revealed that GS degradation is promoted by C-P lyase via the sarcosine pathway, i.e., initial cleavage at the C-P bond. We also identified C-P lyase to be responsible for degradation of EDTMP, EABMP, IDMP and AMPA. However, the identification of the metabolite ethylenediaminetri(methylenephosphonic acid) via LC/MS analysis in the test medium during EDTMP degradation indicates a different initial cleavage step as compared to GS. For EDTMP, it is evident that the initial cleavage occurs at the C-N bond. The detection of different key enzymes at regulated levels, form the bacterial proteoms during EDTMP exposure, further supports this finding. This study illustrates that widely used and structurally more complex aminophosphonates can be degraded by Ochrobactrum sp. BTU1 via the well-known degradation pathways but with different initial cleavage strategy compared to GS.
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Affiliation(s)
- Ramona Riedel
- Chair of Biotechnology of Water Treatment Brandenburg, Institute of Environmental Technology, BTU Cottbus-Senftenberg, Cottbus, Germany.
| | - Fabian M Commichau
- FG Synthetic Microbiology, Institute for Biotechnology, BTU Cottbus-Senftenberg, Senftenberg, Germany; FG Molecular Microbiology, Institute for Biology, University of Hohenheim, Stuttgart, Germany
| | - Dirk Benndorf
- Applied Biosciences and Process Engineering, Anhalt University of Applied Sciences, Köthen, Germany; Chair of Bioprocess Engineering, Otto von Guericke University, Magdeburg, Germany; Bioprocess Engineering, Max Planck Institute for Dynamics of Complex Technical Systems, Magdeburg, Germany
| | - Robert Hertel
- FG Synthetic Microbiology, Institute for Biotechnology, BTU Cottbus-Senftenberg, Senftenberg, Germany; Department of Genomic and Applied Microbiology, Institute of Microbiology and Genetics, Georg-August-University of Göttingen, Göttingen, Germany
| | - Katharina Holzer
- Department of Livestock Infectiology and Environmental Hygiene, Institute of Animal Science, University of Hohenheim, Stuttgart, Germany
| | - Ludwig E Hoelzle
- Department of Livestock Infectiology and Environmental Hygiene, Institute of Animal Science, University of Hohenheim, Stuttgart, Germany
| | - Mohammad Saba Yousef Mardoukhi
- Chair of Biotechnology of Water Treatment Brandenburg, Institute of Environmental Technology, BTU Cottbus-Senftenberg, Cottbus, Germany; FG Synthetic Microbiology, Institute for Biotechnology, BTU Cottbus-Senftenberg, Senftenberg, Germany; FG Molecular Microbiology, Institute for Biology, University of Hohenheim, Stuttgart, Germany
| | - Laura Emelie Noack
- Chair of Biotechnology of Water Treatment Brandenburg, Institute of Environmental Technology, BTU Cottbus-Senftenberg, Cottbus, Germany
| | - Marion Martienssen
- Chair of Biotechnology of Water Treatment Brandenburg, Institute of Environmental Technology, BTU Cottbus-Senftenberg, Cottbus, Germany
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McCarthy WP, Srinivas M, Danaher M, Connor CO, Callaghan TFO, van Sinderen D, Kenny J, Tobin JT. Isolation and identification of chlorate-reducing Hafnia sp. from milk. MICROBIOLOGY (READING, ENGLAND) 2023; 169:001347. [PMID: 37450378 PMCID: PMC10433419 DOI: 10.1099/mic.0.001347] [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: 09/26/2022] [Accepted: 05/31/2023] [Indexed: 07/18/2023]
Abstract
Chlorate has become a concern in the food and beverage sector, related to chlorine sanitizers in industrial food production and water treatment. It is of particular concern to regulatory bodies due to the negative health effects of chlorate exposure. This study investigated the fate of chlorate in raw milk and isolated bacterial strains of interest responsible for chlorate breakdown. Unpasteurized milk was demonstrated to have a chlorate-reducing capacity, breaking down enriched chlorate to undetectable levels in 11 days. Further enrichment and isolation using conditions specific to chlorate-reducing bacteria successfully isolated three distinct strains of Hafnia paralvei. Chlorate-reducing bacteria were observed to grow in a chlorate-enriched medium with lactate as an electron donor. All isolated strains were demonstrated to reduce chlorate in liquid medium; however, the exact mechanism of chlorate degradation was not definitively identified in this study.
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Affiliation(s)
- William P. McCarthy
- Food Chemistry and Technology Department, Teagasc Food Research Centre, Moorepark, Fermoy, Cork, Ireland
- School of Food Science and Environmental Health, Technological University Dublin, Grangegorman, Dublin 7, Ireland
| | - Meghana Srinivas
- Food Biosciences Department, Teagasc Food Research Centre, Moorepark, Fermoy, Cork, Ireland
- School of Microbiology, University College Cork, Cork, Ireland
- APC Microbiome Ireland, University College Cork, Cork, Ireland
| | - Martin Danaher
- Food Safety Department, Teagasc Food Research Centre, Ashtown, Dublin 15, Ireland
| | - Christine O. Connor
- School of Food Science and Environmental Health, Technological University Dublin, Grangegorman, Dublin 7, Ireland
| | - Tom F. O. Callaghan
- School of Food and Nutritional Sciences, University College Cork, Cork, Ireland
| | - Douwe van Sinderen
- School of Microbiology, University College Cork, Cork, Ireland
- APC Microbiome Ireland, University College Cork, Cork, Ireland
| | - John Kenny
- Food Biosciences Department, Teagasc Food Research Centre, Moorepark, Fermoy, Cork, Ireland
- VistaMilk Science Foundation Ireland Research Centre, Teagasc, Moorepark, Fermoy, Cork, Ireland
| | - John T. Tobin
- Food Chemistry and Technology Department, Teagasc Food Research Centre, Moorepark, Fermoy, Cork, Ireland
- VistaMilk Science Foundation Ireland Research Centre, Teagasc, Moorepark, Fermoy, Cork, Ireland
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Li Y, Su J, Ali A, Hao Z, Li M, Yang W, Wang Z. Simultaneous removal of nitrate and heavy metals in a biofilm reactor filled with modified biochar. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 851:158175. [PMID: 35995173 DOI: 10.1016/j.scitotenv.2022.158175] [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: 03/08/2022] [Revised: 07/06/2022] [Accepted: 08/16/2022] [Indexed: 06/15/2023]
Abstract
A biofilm reactor filled with chia seeds gum modified biochar was set up for the simultaneous removal of nitrate, cadmium and zinc from calcium-containing wastewater via denitrification and microbially-induced (calcium) carbonate precipitation. The reactor performance was studied under different conditions of pH, Cd concentration, and hydraulic retention time. The optimal removal efficiency of the reactor for NO3--N, Ca2+, Cd2+, and Zn2+ were 99.98, 79.89, 100, and 99.84 %, respectively. 3D-EEM indicated the aromatic compounds confirming the stability of the reactor. FTIR illustrated the presence of -OH, CaCO3, C-O-C, and C-O-H indicating the precipitation and role of gum in MICP. SEM confirmed that the seed crystal induced the repeated crystallization of free metal ions. XRD showed that heavy metals were removed in the form of CaCO3, CdCO3, ZnCO3, Ca3(PO3)2, Cd3(PO3)2, and Zn3(PO3)2 co-crystallization. SEM-EDS showed the composition and distribution of elements. High-throughput sequencing showed that Curpriavidus sp. GMF1 and Ochrobactrum sp. GMC12 were the dominant bacterial species, with powerful denitrification and MICP mineralization capabilities.
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Affiliation(s)
- Yifei Li
- School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China
| | - Junfeng Su
- School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China.
| | - Amjad Ali
- School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China.
| | - Zhenle Hao
- School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China
| | - Min Li
- School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China
| | - Wenshuo Yang
- School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China
| | - Zhao Wang
- School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China
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Granatto CF, Grosseli GM, Sakamoto IK, Fadini PS, Varesche MBA. Influence of cosubstrate and hydraulic retention time on the removal of drugs and hygiene products in sanitary sewage in an anaerobic Expanded Granular Sludge Bed reactor. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2021; 299:113532. [PMID: 34614559 DOI: 10.1016/j.jenvman.2021.113532] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Revised: 07/24/2021] [Accepted: 08/09/2021] [Indexed: 06/13/2023]
Abstract
Diclofenac (DCF), ibuprofen (IBU), propranolol (PRO), triclosan (TCS) and linear alkylbenzene sulfonate (LAS) can be recalcitrant in Wastewater Treatment Plants (WWTP). The removal of these compounds was investigated in scale-up (69 L) Expanded Granular Sludge Bed (EGSB) reactor, fed with sanitary sewage from the São Carlos-SP (Brazil) WWTP and 200 mg L-1 of ethanol. The EGSB was operated in three phases: (I) hydraulic retention time (HRT) of 36±4 h; (II) HRT of 20±2 h and (III) HRT of 20±2 h with ethanol. Phases I and II showed no significant difference in the removal of LAS (63 ± 11-65 ± 12 %), DCF (37 ± 18-35 ± 11 %), IBU (43 ± 18-44 ± 16 %) and PRO (46 ± 25-51 ± 23 %) for 13±2-15 ± 2 mg L-1, 106 ± 32-462 ± 294 μg L-1, 166 ± 55-462 ± 213 μg L-1 and 201 ± 113-250 ± 141 μg L-1 influent, respectively. Higher TCS removal was obtained in phase I (72 ± 17 % for 127 ± 120 μg L-1 influent) when compared to phase II (51 ± 13 % for 135 ± 119 μg L-1 influent). This was due to its greater adsorption (40 %) in the initial phase. Phase III had higher removal of DCF (42 ± 10 % for 107 ± 26 μg L-1 influent), IBU (50 ± 15 % for 164 ± 47 μg L-1 influent) and TCS (85 ± 15 % for 185 ± 148 μg L-1 influent) and lower removal of LAS (35 ± 14 % for 12 ± 3 mg L-1 influent) and PRO (-142 ± 177 % for 188 ± 88 μg L-1 influent). Bacteria similar to Syntrophobacter, Smithella, Macellibacteroides, Syntrophus, Blvii28_wastewater-sludge_group and Bacteroides were identified in phase I with relative abundance of 3.1 %-4.7 %. Syntrophobacter was more abundant (15.4 %) in phase II, while in phase III, it was Smithella (12.7 %) and Caldisericum (15.1 %). Regarding the Archaea Domain, Methanosaeta was more abundant in phases I (84 %) and II (67 %), while in phase III it was Methanobacterium (86 %).
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Affiliation(s)
- Caroline F Granatto
- Department of Hydraulics and Sanitation, São Carlos School of Engineering, University of São Paulo, Ave Trabalhador São-Carlense, No. 400, Zipcode 13566-590, São Carlos, SP, Brazil.
| | - Guilherme M Grosseli
- Federal University of São Carlos, Washington LuizHighway, Km 235, Zipcode 13565-905, São Carlos, SP, Brazil.
| | - Isabel K Sakamoto
- Department of Hydraulics and Sanitation, São Carlos School of Engineering, University of São Paulo, Ave Trabalhador São-Carlense, No. 400, Zipcode 13566-590, São Carlos, SP, Brazil.
| | - Pedro S Fadini
- Federal University of São Carlos, Washington LuizHighway, Km 235, Zipcode 13565-905, São Carlos, SP, Brazil.
| | - Maria Bernadete A Varesche
- Department of Hydraulics and Sanitation, São Carlos School of Engineering, University of São Paulo, Ave Trabalhador São-Carlense, No. 400, Zipcode 13566-590, São Carlos, SP, Brazil.
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Yu YH, Su JF, Shih Y, Wang J, Wang PY, Huang CP. Hazardous wastes treatment technologies. WATER ENVIRONMENT RESEARCH : A RESEARCH PUBLICATION OF THE WATER ENVIRONMENT FEDERATION 2020; 92:1833-1860. [PMID: 32866315 DOI: 10.1002/wer.1447] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2020] [Revised: 08/24/2020] [Accepted: 08/26/2020] [Indexed: 06/11/2023]
Abstract
A review of the literature published in 2019 on topics related to hazardous waste management in water, soils, sediments, and air. The review covered treatment technologies applying physical, chemical, and biological principles for the remediation of contaminated water, soils, sediments, and air. PRACTICAL POINTS: This report provides a review of technologies for the management of waters, wastewaters, air, sediments, and soils contaminated by various hazardous chemicals including inorganic (e.g., oxyanions, salts, and heavy metals), organic (e.g., halogenated, pharmaceuticals and personal care products, pesticides, and persistent organic chemicals) in three scientific areas of physical, chemical, and biological methods. Physical methods for the management of hazardous wastes including general adsorption, sand filtration, coagulation/flocculation, electrodialysis, electrokinetics, electro-sorption ( capacitive deionization, CDI), membrane (RO, NF, MF), photocatalysis, photoelectrochemical oxidation, sonochemical, non-thermal plasma, supercritical fluid, electrochemical oxidation, and electrochemical reduction processes were reviewed. Chemical methods including ozone-based, hydrogen peroxide-based, potassium permanganate processes, and Fenton and Fenton-like process were reviewed. Biological methods such as aerobic, anoxic, anaerobic, bioreactors, constructed wetlands, soil bioremediation and biofilter processes for the management of hazardous wastes, in mode of consortium and pure culture were reviewed. Case histories were reviewed in four areas including contaminated sediments, contaminated soils, mixed industrial solid wastes and radioactive wastes.
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Affiliation(s)
- Yu Han Yu
- Department of Civil and Environmental Engineering, University of Delaware, Newark, Delaware, USA
| | - Jenn Fang Su
- Department of Chemical and Materials Engineering, Tamkang University, New Taipei City, Taiwan
| | - Yujen Shih
- Graduate Institute of Environmental Essngineering, National Sun yat-sen University, Kaohsiung, Taiwan
| | - Jianmin Wang
- Department of Civil Architectural and Environmental Engineering, Missouri University of Science & Technology, Rolla, Missouri
| | - Po Yen Wang
- Department of Civil Engineering, Widener University, Chester, Pennsylvania, USA
| | - Chin Pao Huang
- Department of Civil and Environmental Engineering, University of Delaware, Newark, Delaware, USA
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Evaluating the Effect of Azole Antifungal Agents on the Stress Response and Nanomechanical Surface Properties of Ochrobactrum anthropi Aspcl2.2. Molecules 2020; 25:molecules25153348. [PMID: 32717971 PMCID: PMC7435821 DOI: 10.3390/molecules25153348] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 07/17/2020] [Accepted: 07/20/2020] [Indexed: 12/03/2022] Open
Abstract
Azole antifungal molecules are broadly used as active ingredients in various products, such as pharmaceuticals and pesticides. This promotes their release into the natural environment. The detailed mechanism of their influence on the biotic components of natural ecosystems remains unexplored. Our research aimed to examine the response of Ochrobactrum anthropi AspCl2.2 to the presence of four azole antifungal agents (clotrimazole, fluconazole, climbazole, epoxiconazole). The experiments performed include analysis of the cell metabolic activity, cell membrane permeability, total glutathione level and activity of glutathione S-transferases. These studies allowed for the evaluation of the cells’ oxidative stress response to the presence of azole antifungals. Moreover, changes in the nanomechanical surface properties, including adhesive and elastic features of the cells, were investigated using atomic force microscopy (AFM) and spectrophotometric methods. The results indicate that the azoles promote bacterial oxidative stress. The strongest differences were noted for the cells cultivated with fluconazole. The least toxic effect has been attributed to climbazole. AFM observations unraveled molecular details of bacterial cell texture, structure and surface nanomechanical properties. Antifungals promote the nanoscale modification of the bacterial cell wall. The results presented provided a significant insight into the strategies used by environmental bacterial cells to survive exposures to toxic azole antifungal agents.
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Kinetics and New Mechanism of Azoxystrobin Biodegradation by an Ochrobactrum anthropi Strain SH14. Microorganisms 2020; 8:microorganisms8050625. [PMID: 32357564 PMCID: PMC7284741 DOI: 10.3390/microorganisms8050625] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 04/14/2020] [Accepted: 04/23/2020] [Indexed: 11/24/2022] Open
Abstract
Azoxystrobin is one of the most popular strobilurin fungicides, widely used in agricultural fields for decades.Extensive use of azoxystrobin poses a major threat to ecosystems. However, little is known about the kinetics and mechanism of azoxystrobin biodegradation. The present study reports a newly isolated bacterial strain, Ochrobactrum anthropi SH14, utilizing azoxystrobin as a sole carbon source, was isolated from contaminated soils. Strain SH14 degraded 86.3% of azoxystrobin (50 μg·mL−1) in a mineral salt medium within five days. Maximum specific degradation rate (qmax), half-saturation constant (Ks), and inhibition constant (Ki) were noted as 0.6122 d−1, 6.8291 μg·mL−1, and 188.4680 μg·mL−1, respectively.Conditions for strain SH14 based azoxystrobin degradation were optimized by response surface methodology. Optimum degradation was determined to be 30.2 °C, pH 7.9, and 1.1 × 107 CFU·mL−1 of inoculum. Strain SH14 degraded azoxystrobin via a novel metabolic pathway with the formation of N-(4,6-dimethoxypyrimidin-2-yl)-acetamide,2-amino-4-(4-chlorophenyl)-3-cyano-5,6-dimethyl-pyridine, and 3-quinolinecarboxylic acid,6,8-difluoro-4-hydroxy-ethyl ester as the main intermediate products, which were further transformed without any persistent accumulative product. This is the first report of azoxystrobin degradation pathway in a microorganism. Strain SH14 also degraded other strobilurin fungicides, including kresoxim-methyl (89.4%), pyraclostrobin (88.5%), trifloxystrobin (78.7%), picoxystrobin (76.6%), and fluoxastrobin (57.2%) by following first-order kinetic model. Bioaugmentation of azoxystrobin-contaminated soils with strain SH14 remarkably enhanced the degradation of azoxystrobin, and its half-life was substantially reduced by 95.7 and 65.6 days in sterile and non-sterile soils, respectively, in comparison with the controls without strain SH14. The study presents O. anthropi SH14 for enhanced biodegradation of azoxystrobin and elaborates on the metabolic pathways to eliminate its residual toxicity from the environment.
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