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Bopp C, Bernet NM, Meyer F, Khan R, Robinson SL, Kohler HPE, Buller R, Hofstetter TB. Elucidating the Role of O 2 Uncoupling for the Adaptation of Bacterial Biodegradation Reactions Catalyzed by Rieske Oxygenases. ACS ENVIRONMENTAL AU 2024; 4:204-218. [PMID: 39035869 PMCID: PMC11258757 DOI: 10.1021/acsenvironau.4c00016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/04/2024] [Revised: 04/26/2024] [Accepted: 04/26/2024] [Indexed: 07/23/2024]
Abstract
Oxygenation of aromatic and aliphatic hydrocarbons by Rieske oxygenases is the initial step of various biodegradation pathways for environmental organic contaminants. Microorganisms carrying Rieske oxygenases are able to quickly adapt their substrate spectra to alternative carbon and energy sources that are structurally related to the original target substrate, yet the molecular events responsible for this rapid adaptation are not well understood. Here, we evaluated the hypothesis that reactive oxygen species (ROS) generated by unproductive activation of O2, the so-called O2 uncoupling, in the presence of the alternative substrate exert a selective pressure on the bacterium for increasing the oxygenation efficiency of Rieske oxygenases. To that end, we studied wild-type 2-nitrotoluene dioxygenase from Acidovorax sp. strain JS42 and five enzyme variants that have evolved from adaptive laboratory evolution experiments with 3- and 4-nitrotoluene as alternative growth substrates. The enzyme variants showed a substantially increased oxygenation efficiency toward the new target substrates concomitant with a reduction of ROS production, while mechanisms and kinetics of enzymatic O2 activation remained unchanged. Structural analyses and docking studies suggest that amino acid substitutions in enzyme variants occurred at residues lining both substrate and O2 transport tunnels, enabling tighter binding of the target substrates in the active site. Increased oxygenation efficiencies measured in vitro for the various enzyme (variant)-substrate combinations correlated linearly with in vivo changes in growth rates for evolved Acidovorax strains expressing the variants. Our data suggest that the selective pressure from oxidative stress toward more efficient oxygenation by Rieske oxygenases was most notable when O2 uncoupling exceeded 60%.
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Affiliation(s)
- Charlotte
E. Bopp
- Eawag,
Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
- Institute
of Biogeochemistry and Pollutant Dynamics (IBP), ETH Zürich, 8092 Zürich, Switzerland
| | - Nora M. Bernet
- Eawag,
Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
- Institute
of Biogeochemistry and Pollutant Dynamics (IBP), ETH Zürich, 8092 Zürich, Switzerland
| | - Fabian Meyer
- Competence
Center for Biocatalysis, Institute of Chemistry and Biotechnology, Zürich University of Applied Sciences, 8820 Wädenswil, Switzerland
| | - Riyaz Khan
- Eawag,
Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
| | - Serina L. Robinson
- Eawag,
Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
| | - Hans-Peter E. Kohler
- Eawag,
Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
| | - Rebecca Buller
- Competence
Center for Biocatalysis, Institute of Chemistry and Biotechnology, Zürich University of Applied Sciences, 8820 Wädenswil, Switzerland
| | - Thomas B. Hofstetter
- Eawag,
Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
- Institute
of Biogeochemistry and Pollutant Dynamics (IBP), ETH Zürich, 8092 Zürich, Switzerland
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2
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Xu J, Li T, Huang WE, Zhou NY. Semi-rational design of nitroarene dioxygenase for catalytic ability toward 2,4-dichloronitrobenzene. Appl Environ Microbiol 2024; 90:e0143623. [PMID: 38709097 PMCID: PMC11218619 DOI: 10.1128/aem.01436-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Accepted: 04/05/2024] [Indexed: 05/07/2024] Open
Abstract
Rieske non-heme dioxygenase family enzymes play an important role in the aerobic biodegradation of nitroaromatic pollutants, but no active dioxygenases are available in nature for initial reactions in the degradation of many refractory pollutants like 2,4-dichloronitrobenzene (24DCNB). Here, we report the engineering of hotspots in 2,3-dichloronitrobenzene dioxygenase from Diaphorobacter sp. strain JS3051, achieved through molecular dynamic simulation analysis and site-directed mutagenesis, with the aim of enhancing its catalytic activity toward 24DCNB. The computationally predicted activity scores were largely consistent with the detected activities in wet experiments. Among them, the two most beneficial mutations (E204M and M248I) were obtained, and the combined mutant reached up to a 62-fold increase in activity toward 24DCNB, generating a single product, 3,5-dichlorocatechol, which is a naturally occurring compound. In silico analysis confirmed that residue 204 affected the substrate preference for meta-substituted nitroarenes, while residue 248 may influence substrate preference by interaction with residue 295. Overall, this study provides a framework for manipulating nitroarene dioxygenases using computational methods to address various nitroarene contamination problems.IMPORTANCEAs a result of human activities, various nitroaromatic pollutants continue to enter the biosphere with poor degradability, and dioxygenation is an important kickoff step to remove toxic nitro-groups and convert them into degradable products. The biodegradation of many nitroarenes has been reported over the decades; however, many others still lack corresponding enzymes to initiate their degradation. Although rieske non-heme dioxygenase family enzymes play extraordinarily important roles in the aerobic biodegradation of various nitroaromatic pollutants, prediction of their substrate specificity is difficult. This work greatly improved the catalytic activity of dioxygenase against 2,4-dichloronitrobenzene by computer-aided semi-rational design, paving a new way for the evolution strategy of nitroarene dioxygenase. This study highlights the potential for using enzyme structure-function information with computational pre-screening methods to rapidly tailor the catalytic functions of enzymes toward poorly biodegradable contaminants.
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Affiliation(s)
- Jia Xu
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Tao Li
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Wei E. Huang
- Department of Engineering Science, University of Oxford, Oxford, United Kingdom
| | - Ning-Yi Zhou
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
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3
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Haq IU, Christensen A, Fixen KR. Evolution of Rhodopseudomonas palustris to degrade halogenated aromatic compounds involves changes in pathway regulation and enzyme specificity. Appl Environ Microbiol 2024; 90:e0210423. [PMID: 38206012 PMCID: PMC10880631 DOI: 10.1128/aem.02104-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Accepted: 12/15/2023] [Indexed: 01/12/2024] Open
Abstract
Halogenated aromatic compounds are used in a variety of industrial applications but can be harmful to humans and animals when released into the environment. Microorganisms that degrade halogenated aromatic compounds anaerobically have been isolated but the evolutionary path that they may have taken to acquire this ability is not well understood. A strain of the purple nonsulfur bacterium, Rhodopseudomonas palustris, RCB100, can use 3-chlorobenzoate (3-CBA) as a carbon source whereas a closely related strain, CGA009, cannot. To reconstruct the evolutionary events that enabled RCB100 to degrade 3-CBA, we isolated an evolved strain derived from CGA009 capable of growing on 3-CBA. Comparative whole-genome sequencing of the evolved strain and RCB100 revealed both strains contained large deletions encompassing badM, a transcriptional repressor of genes for anaerobic benzoate degradation. It was previously shown that in strain RCB100, a single nucleotide change in an alicyclic acid coenzyme A ligase gene, named aliA, gives rise to a variant AliA enzyme that has high activity with 3-CBA. When the RCB100 aliA allele and a deletion in badM were introduced into R. palustris CGA009, the resulting strain grew on 3-CBA at a similar rate as RCB100. This work provides an example of pathway evolution in which regulatory constraints were overcome to enable the selection of a variant of a promiscuous enzyme with enhanced substrate specificity.IMPORTANCEBiodegradation of man-made compounds often involves the activity of promiscuous enzymes whose native substrate is structurally similar to the man-made compound. Based on the enzymes involved, it is possible to predict what microorganisms are likely involved in biodegradation of anthropogenic compounds. However, there are examples of organisms that contain the required enzyme(s) and yet cannot metabolize these compounds. We found that even when the purple nonsulfur bacterium, Rhodopseudomonas palustris, encodes all the enzymes required for degradation of a halogenated aromatic compound, it is unable to metabolize that compound. Using adaptive evolution, we found that a regulatory mutation and a variant of promiscuous enzyme with increased substrate specificity were required. This work provides insight into how an environmental isolate evolved to use a halogenated aromatic compound.
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Affiliation(s)
- Irshad Ul Haq
- Department of Plant and Microbial Biology, College of Biological Sciences, University of Minnesota, Saint Paul, Minnesota, USA
- Department of Plant and Microbial Biology, BioTechnology Institute, University of Minnesota, Saint Paul, Minnesota, USA
| | - Annika Christensen
- Department of Plant and Microbial Biology, College of Biological Sciences, University of Minnesota, Saint Paul, Minnesota, USA
- Department of Plant and Microbial Biology, BioTechnology Institute, University of Minnesota, Saint Paul, Minnesota, USA
| | - Kathryn R. Fixen
- Department of Plant and Microbial Biology, College of Biological Sciences, University of Minnesota, Saint Paul, Minnesota, USA
- Department of Plant and Microbial Biology, BioTechnology Institute, University of Minnesota, Saint Paul, Minnesota, USA
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Brar B, Kumar R, Sharma D, Sharma AK, Thakur K, Mahajan D, Kumar R. Metagenomic analysis reveals diverse microbial community and potential functional roles in Baner rivulet, India. J Genet Eng Biotechnol 2023; 21:147. [PMID: 38015339 PMCID: PMC10684477 DOI: 10.1186/s43141-023-00601-x] [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: 05/18/2023] [Accepted: 11/14/2023] [Indexed: 11/29/2023]
Abstract
BACKGROUND The health index of any population is directly correlated with the water quality, which in turn depends upon physicochemical characteristics and the microbiome of that aquatic source. For maintaining the water quality, knowledge of microbial diversity is a must. The present investigation attempts to evaluate the microflora of Baner. Metagenomics has been proven to be the technique for examining the genetic diversity of unculturable microbiota without using traditional culturing techniques. The microbial profile of Baner is analyzed using metagenomics for the first time to the best of our knowledge. RESULTS To explore the microbial diversity of Baner, metagenomics analysis from 3 different sites was done. Data analysis identified 29 phyla, 62 classes, 131 orders, 268 families, and 741 genera. Proteobacteria was found to be the most abundant phylum in all the sampling sites, with the highest abundance at S3 sampling site (94%). Bacteroidetes phylum was found to be second abundant in S1 and S2 site, whereas Actinobacteria was second dominant in sampling site S3. Enterobacteriaceae family was dominant in site S1, whereas Comamonadaceae and Pseudomonadaceae was abundant in sites S2 and S3 respectively. The Baner possesses an abundant bacterial profile that holds great promise for developing bioremediation tactics against a variety of harmful substances. CONCLUSION Baner river's metagenomic analysis offers the first insight into the microbial profile of this hilly stream. Proteobacteria was found to be the most abundant phylum in all the sampling sites indicating anthropogenic interference and sewage contamination. The highest abundance of proteobacteria at S3 reveals it to be the most polluted site, as it is the last sampling site downstream of the area under investigation, and falls after crossing the main city, so more human intervention and pollution were observed. Despite some pathogens, a rich profile of bacteria involved in bioremediation, xenobiotic degradation, and beneficial fish probiotics was observed, reflecting their potential applications for improving water quality and establishing a healthy aquaculture and fishery section.
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Affiliation(s)
- Bhavna Brar
- Department of Animal Sciences, School of Life Sciences, Central University of Himachal Pradesh, Kangra, Himachal Pradesh, India
| | - Ravi Kumar
- Department of Microbiology, Dr. Rajendra Prasad Government Medical College & Hospital, Tanda, Kangra, Himachal Pradesh, India
| | - Dixit Sharma
- Department of Animal Sciences, School of Life Sciences, Central University of Himachal Pradesh, Kangra, Himachal Pradesh, India
| | - Amit Kumar Sharma
- Department of Animal Sciences, School of Life Sciences, Central University of Himachal Pradesh, Kangra, Himachal Pradesh, India
| | - Kushal Thakur
- Department of Animal Sciences, School of Life Sciences, Central University of Himachal Pradesh, Kangra, Himachal Pradesh, India
| | - Danish Mahajan
- Department of Animal Sciences, School of Life Sciences, Central University of Himachal Pradesh, Kangra, Himachal Pradesh, India
| | - Rakesh Kumar
- Department of Animal Sciences, School of Life Sciences, Central University of Himachal Pradesh, Kangra, Himachal Pradesh, India.
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5
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Bopp CE, Bernet NM, Kohler HPE, Hofstetter TB. Elucidating the Role of O 2 Uncoupling in the Oxidative Biodegradation of Organic Contaminants by Rieske Non-heme Iron Dioxygenases. ACS ENVIRONMENTAL AU 2022; 2:428-440. [PMID: 36164353 PMCID: PMC9502038 DOI: 10.1021/acsenvironau.2c00023] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
Oxygenations of aromatic
soil and water contaminants with molecular
O2 catalyzed by Rieske dioxygenases are frequent initial
steps of biodegradation in natural and engineered environments. Many
of these non-heme ferrous iron enzymes are known to be involved in
contaminant metabolism, but the understanding of enzyme–substrate
interactions that lead to successful biodegradation is still elusive.
Here, we studied the mechanisms of O2 activation and substrate
hydroxylation of two nitroarene dioxygenases to evaluate enzyme- and
substrate-specific factors that determine the efficiency of oxygenated
product formation. Experiments in enzyme assays of 2-nitrotoluene
dioxygenase (2NTDO) and nitrobenzene dioxygenase (NBDO) with methyl-,
fluoro-, chloro-, and hydroxy-substituted nitroaromatic substrates
reveal that typically 20–100% of the enzyme’s activity
involves unproductive paths of O2 activation with generation
of reactive oxygen species through so-called O2 uncoupling.
The 18O and 13C kinetic isotope effects of O2 activation and nitroaromatic substrate hydroxylation, respectively,
suggest that O2 uncoupling occurs after generation of FeIII-(hydro)peroxo species in the catalytic cycle. While 2NTDO
hydroxylates ortho-substituted nitroaromatic substrates
more efficiently, NBDO favors meta-substituted, presumably
due to distinct active site residues of the two enzymes. Our data
implies, however, that the O2 uncoupling and hydroxylation
activity cannot be assessed from simple structure–reactivity
relationships. By quantifying O2 uncoupling by Rieske dioxygenases,
our work provides a mechanistic link between contaminant biodegradation,
the generation of reactive oxygen species, and possible adaptation
strategies of microorganisms to the exposure of new contaminants.
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Affiliation(s)
- Charlotte E. Bopp
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
- Institute of Biogeochemistry and Pollutant Dynamics (IBP), ETH Zürich, 8092 Zürich, Switzerland
| | - Nora M. Bernet
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
| | - Hans-Peter E. Kohler
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
| | - Thomas B. Hofstetter
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
- Institute of Biogeochemistry and Pollutant Dynamics (IBP), ETH Zürich, 8092 Zürich, Switzerland
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6
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Gao YZ, Palatucci ML, Waidner LA, Li T, Guo Y, Spain JC, Zhou NY. A Nag-like dioxygenase initiates 3,4-dichloronitrobenzene degradation via 4,5-dichlorocatechol in Diaphorobacter sp. strain JS3050. Environ Microbiol 2020; 23:1053-1065. [PMID: 33103811 DOI: 10.1111/1462-2920.15295] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 10/20/2020] [Accepted: 10/23/2020] [Indexed: 11/30/2022]
Abstract
The chemical synthesis intermediate 3,4-dichloronitrobenzene (3,4-DCNB) is an environmental pollutant. Diaphorobacter sp. strain JS3050 utilizes 3,4-DCNB as a sole source of carbon, nitrogen and energy. However, the molecular determinants of its catabolism are poorly understood. Here, the complete genome of strain JS3050 was sequenced and key genes were expressed heterologously to establish the details of its degradation pathway. A chromosome-encoded three-component nitroarene dioxygenase (DcnAaAbAcAd) converted 3,4-DCNB stoichiometrically to 4,5-dichlorocatechol, which was transformed to 3,4-dichloromuconate by a plasmid-borne ring-cleavage chlorocatechol 1,2-dioxygenase (DcnC). On the chromosome, there are also genes encoding enzymes (DcnDEF) responsible for the subsequent transformation of 3,4-dichloromuconate to β-ketoadipic acid. The fact that the genes responsible for the catabolic pathway are separately located on plasmid and chromosome indicates that recent assembly and ongoing evolution of the genes encoding the pathway is likely. The regiospecificity of 4,5-dichlorocatechol formation from 3,4-DCNB by DcnAaAbAcAd represents a sophisticated evolution of the nitroarene dioxygenase that avoids misrouting of toxic intermediates. The findings enhance the understanding of microbial catabolic diversity during adaptive evolution in response to xenobiotics released into the environment.
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Affiliation(s)
- Yi-Zhou Gao
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic and Developmental Sciences, and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Mallory L Palatucci
- Center for Environmental Diagnostics and Bioremediation, University of West Florida, 11000 University Parkway, Pensacola, FL, 32514-5751, USA
| | - Lisa A Waidner
- Center for Environmental Diagnostics and Bioremediation, University of West Florida, 11000 University Parkway, Pensacola, FL, 32514-5751, USA
| | - Tao Li
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic and Developmental Sciences, and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Yuan Guo
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic and Developmental Sciences, and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Jim C Spain
- Center for Environmental Diagnostics and Bioremediation, University of West Florida, 11000 University Parkway, Pensacola, FL, 32514-5751, USA
| | - Ning-Yi Zhou
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic and Developmental Sciences, and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240, China
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Rahimi S, Modin O, Mijakovic I. Technologies for biological removal and recovery of nitrogen from wastewater. Biotechnol Adv 2020; 43:107570. [PMID: 32531318 DOI: 10.1016/j.biotechadv.2020.107570] [Citation(s) in RCA: 127] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 05/22/2020] [Accepted: 05/22/2020] [Indexed: 12/11/2022]
Abstract
Water contamination is a growing environmental issue. Several harmful effects on human health and the environment are attributed to nitrogen contamination of water sources. Consequently, many countries have strict regulations on nitrogen compound concentrations in wastewater effluents. Wastewater treatment is carried out using energy- and cost-intensive biological processes, which convert nitrogen compounds into innocuous dinitrogen gas. On the other hand, nitrogen is also an essential nutrient. Artificial fertilizers are produced by fixing dinitrogen gas from the atmosphere, in an energy-intensive chemical process. Ideally, we should be able to spend less energy and chemicals to remove nitrogen from wastewater and instead recover a fraction of it for use in fertilizers and similar applications. In this review, we present an overview of various technologies of biological nitrogen removal including nitrification, denitrification, anaerobic ammonium oxidation (anammox), as well as bioelectrochemical systems and microalgal growth for nitrogen recovery. We highlighted the nitrogen removal efficiency of these systems at different temperatures and operating conditions. The advantages, practical challenges, and potential for nitrogen recovery of different treatment methods are discussed.
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Affiliation(s)
- Shadi Rahimi
- Division of Systems and Synthetic Biology, Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden.
| | - Oskar Modin
- Division of Water Environment Technology, Department of Architecture and Civil Engineering, Chalmers University of Technology, Gothenburg, Sweden
| | - Ivan Mijakovic
- Division of Systems and Synthetic Biology, Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden; The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Lyngby, Denmark.
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A Bph-Like Nitroarene Dioxygenase Catalyzes the Conversion of 3-Nitrotoluene to 3-Methylcatechol by Rhodococcus sp. Strain ZWL3NT. Appl Environ Microbiol 2020; 86:AEM.02517-19. [PMID: 31811044 DOI: 10.1128/aem.02517-19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Accepted: 11/27/2019] [Indexed: 11/20/2022] Open
Abstract
All nitroarene dioxygenases reported so far originated from Nag-like naphthalene dioxygenase of Gram-negative strains, belonging to group III of aromatic ring-hydroxylating oxygenases (RHOs). Gram-positive Rhodococcus sp. strain ZWL3NT utilizes 3-nitrotoluene (3NT) as the sole source of carbon, nitrogen, and energy for growth. It was also reported that 3NT degradation was constitutive and the intermediate was 3-methylcatechol. In this study, a gene cluster (bndA1A2A3A4) encoding a multicomponent dioxygenase, belonging to group IV of RHOs, was identified. Recombinant Rhodococcus imtechensis RKJ300 carrying bndA1A2A3A4 exhibited 3NT dioxygenase activity, converting 3NT into 3-methylcatechol exclusively, with nitrite release. The identity of the product 3-methylcatechol was confirmed using liquid chromatography-mass spectrometry. A time course of biotransformation showed that the 3NT consumption was almost equal to the 3-methylcatechol accumulation, indicating a stoichiometry conversion of 3NT to 3-methylcatechol. Unlike reported Nag-like dioxygenases transforming 3NT into 4-methylcatechol or both 4-methylcatechol and 3-methylcatechol, this Bph-like dioxygenase (dioxygenases homologous to the biphenyl dioxygenase from Rhodococcus sp. strain RHA1) converts 3NT to 3-methylcatechol without forming 4-methylcatechol. Furthermore, whole-cell biotransformation of strain RKJ300 with bndA1A2A3A4 and strain ZWL3NT exhibited the extended and same substrate specificity against a number of nitrobenzene or substituted nitrobenzenes, suggesting that BndA1A2A3A4 is likely the native form of 3NT dioxygenase in strain ZWL3NT.IMPORTANCE Nitroarenes are synthetic molecules widely used in the chemical industry. Microbial degradation of nitroarenes has attracted extensive attention, not only because this class of xenobiotic compounds is recalcitrant in the environment but also because the microbiologists working in this field are curious about the evolutionary origin and process of the nitroarene dioxygenases catalyzing the initial reaction in the catabolism. In contrast to previously reported nitroarene dioxygenases from Gram-negative strains, which originated from a Nag-like naphthalene dioxygenase, the 3-nitrotoluene (3NT) dioxygenase in this study is from a Gram-positive strain and is an example of a Bph-like nitroarene dioxygenase. The preference of hydroxylation of this enzyme at the 2,3 positions of the benzene ring to produce 3-methylcatechol exclusively from 3NT is also a unique property among the studied nitroarene dioxygenases. These findings will enrich our understanding of the diversity and origin of nitroarene dioxygenase in microorganisms.
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9
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Tiwari J, Tarale P, Sivanesan S, Bafana A. Environmental persistence, hazard, and mitigation challenges of nitroaromatic compounds. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2019; 26:28650-28667. [PMID: 31388957 DOI: 10.1007/s11356-019-06043-8] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Accepted: 07/22/2019] [Indexed: 05/15/2023]
Abstract
Nitroaromatic compounds (NACs) are extensively used in different industries and are synthesized in large quantity due to their heavy demand worldwide. The broad use of NACs poses a serious pollution threat. The treatment processes used for the removal of NACs are not effective and sustainable, leading to their release into the environment. The nitro group attached to benzene ring makes the compounds recalcitrant due to which they persist in the environment. Being hazardous to human as well as other living organisms, NACs are listed in the USEPA's priority pollutant group. This review provides updated information on the sources of NACs, prevalence in different environmental matrices, and recent developments in methods of their detection, with emphasis on current trends as well as future prospects. The harmful effects of NACs due to exposure through different routes are also highlighted. Further, the technologies reported for the treatment of NACs, including physico-chemical and biological methods, and the challenges faced for their effective implementation are discussed. Thus, the review discusses relevant issues in detail making suitable recommendations, which can be helpful in guiding further research in this subject.
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Affiliation(s)
- Jyoti Tiwari
- AcSIR (Academy of Scientific and Innovative Research), CSIR-NEERI (National Environmental Engineering Research Institute) Campus, Nagpur, 440020, India
- Director's Research Cell, CSIR-NEERI (National Environmental Engineering Research Institute), Nagpur, 440020, Maharashtra, India
| | - Prashant Tarale
- Health and Toxicity Cell, CSIR-NEERI (National Environmental Engineering Research Institute), Nagpur, 440020, India
- Blood Research Institute, Versiti Wisconsin, 8727 Watertown Plank Road, Milwaukee, WI, 53213, USA
| | - Saravanadevi Sivanesan
- AcSIR (Academy of Scientific and Innovative Research), CSIR-NEERI (National Environmental Engineering Research Institute) Campus, Nagpur, 440020, India
- Health and Toxicity Cell, CSIR-NEERI (National Environmental Engineering Research Institute), Nagpur, 440020, India
| | - Amit Bafana
- AcSIR (Academy of Scientific and Innovative Research), CSIR-NEERI (National Environmental Engineering Research Institute) Campus, Nagpur, 440020, India.
- Director's Research Cell, CSIR-NEERI (National Environmental Engineering Research Institute), Nagpur, 440020, Maharashtra, India.
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10
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Zheng XY, Lu D, Wang MY, Chen W, Zhou G, Zhang Y. Effect of chromium (VI) on the multiple nitrogen removal pathways and microbial community of aerobic granular sludge. ENVIRONMENTAL TECHNOLOGY 2018; 39:1682-1696. [PMID: 28562229 DOI: 10.1080/09593330.2017.1337230] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Accepted: 05/26/2017] [Indexed: 06/07/2023]
Abstract
The frequent appearance of Cr(VI) significantly impacts the microbial metabolism in wastewater. In this study, long-term effects of Cr(VI) on microbial community, nitrogen removal pathways and mechanism of aerobic granular sludge (AGS) were investigated. AGS had strong resistance ability to 1.0 mg/L Cr(VI). 3.0 mg/L Cr(VI) increased the heterotrophic-specific ammonia uptake rate (HSAUR) and heterotrophic-specific nitrate uptake rate (HSNUR) transiently, whereas 5.0 mg/L Cr(VI) sharply decreased the specific ammonia uptake rate (SAUR), specific nitrate uptake rate (SNUR) and simultaneous nitrification denitrification rate (SNDR). It was found that Cr (VI) has a greater inhibitory effect on autotrophic nitrification (ASAUR), and the maximal inhibition rate (IR) was 139.19%. Besides, the inhibition of Cr (VI) on nitrogen removal process belongs to non-competitive inhibition. Cr(VI) had a weaker negative impact on heterotrophic bacteria compared with that on autotrophic bacteria. Denaturing gradient gel electrophoresis analyses suggest that Acidovorax sp., flavobacterium sp., uncultured soil bacterium, uncultured nitrosospira sp., uncultured prokaryote, uncultured β-proteobacterium and uncultured pseudomonas sp. were the dominant species. The inhibition of Cr(VI) on nitrite-oxidizing bacteria was the strongest, followed by ammonia-oxidizing bacteria and denitrifying bacteria. Linear correlations between bacterial count and biomass-specific uptake rate were observed when the Cr(VI) concentration exceeded 3 mg/L. This study revealed the effect of Cr(VI) on nitrification is more serious than that on denitrification. Autotrophic and heterotrophic nitrification, heterotrophic denitrification and simultaneous nitrification denitrification played a significant role on nitrogen removal under Cr(VI) stress.
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Affiliation(s)
- Xiao-Ying Zheng
- a Ministry of Education Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes , Hohai University , Nanjing , People's Republic of China
- b College of Environment , Hohai University , Nanjing , People's Republic of China
| | - Dan Lu
- b College of Environment , Hohai University , Nanjing , People's Republic of China
| | - Ming-Yang Wang
- b College of Environment , Hohai University , Nanjing , People's Republic of China
| | - Wei Chen
- a Ministry of Education Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes , Hohai University , Nanjing , People's Republic of China
- b College of Environment , Hohai University , Nanjing , People's Republic of China
| | - Gan Zhou
- b College of Environment , Hohai University , Nanjing , People's Republic of China
| | - Yuan Zhang
- b College of Environment , Hohai University , Nanjing , People's Republic of China
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Li N, Yao L, He Q, Qiu J, Cheng D, Ding D, Tao Q, He J, Jiang J. 3,6-Dichlorosalicylate Catabolism Is Initiated by the DsmABC Cytochrome P450 Monooxygenase System in Rhizorhabdus dicambivorans Ndbn-20. Appl Environ Microbiol 2018; 84:e02133-17. [PMID: 29196293 PMCID: PMC5795090 DOI: 10.1128/aem.02133-17] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Accepted: 11/28/2017] [Indexed: 11/20/2022] Open
Abstract
The degradation of the herbicide dicamba is initiated by demethylation to form 3,6-dichlorosalicylate (3,6-DCSA) in Rhizorhabdusdicambivorans Ndbn-20. In the present study, a 3,6-DCSA degradation-deficient mutant, Ndbn-20m, was screened. A cluster, dsmR1DABCEFGR2, was lost in this mutant. The cluster consisted of nine genes, all of which were apparently induced by 3,6-DCSA. DsmA shared 30 to 36% identity with the monooxygenase components of reported three-component cytochrome P450 systems and formed a monophyletic branch in the phylogenetic tree. DsmB and DsmC were most closely related to the reported [2Fe-2S] ferredoxin and ferredoxin reductase, respectively. The disruption of dsmA in strain Ndbn-20 resulted in inactive 3,6-DCSA degradation. When dsmABC, but not dsmA alone, was introduced into mutant Ndbn-20m and Sphingobium quisquiliarum DC-2 (which is unable to degrade salicylate and its derivatives), they acquired the ability to hydroxylate 3,6-DCSA. Single-crystal X-ray diffraction demonstrated that the DsmABC-catalyzed hydroxylation occurred at the C-5 position of 3,6-DCSA, generating 3,6-dichlorogentisate (3,6-DCGA). In addition, DsmD shared 51% identity with GtdA (a gentisate and 3,6-DCGA 1,2-dioxygenase) from Sphingomonas sp. strain RW5. However, unlike GtdA, the purified DsmD catalyzed the cleavage of gentisate and 3-chlorogentisate but not 6-chlorogentisate or 3,6-DCGA in vitro Based on the bioinformatic analysis and gene function studies, a possible catabolic pathway of dicamba in R. dicambivorans Ndbn-20 was proposed.IMPORTANCE Dicamba is widely used to control a variety of broadleaf weeds and is a promising target herbicide for the engineering of herbicide-resistant crops. The catabolism of dicamba has thus received increasing attention. Bacteria mineralize dicamba initially via demethylation, generating 3,6-dichlorosalicylate. However, the catabolism of 3,6-dichlorosalicylate remains unknown. In this study, we cloned a gene cluster, dsmR1DABCEFGR2, involved in 3,6-dichlorosalicylate degradation from R. dicambivorans Ndbn-20, demonstrated that the cytochrome P450 monooxygenase system DsmABC was responsible for the 5-hydroxylation of 3,6-dichlorosalicylate, and proposed a dicamba catabolic pathway. This study provides a basis to elucidate the catabolism of dicamba and has benefits for the ecotoxicological study of dicamba. Furthermore, the hydroxylation of salicylate has been previously reported to be catalyzed by single-component flavoprotein or three-component Rieske non-heme iron oxygenase, whereas DsmABC was the only cytochrome P450 monooxygenase system hydroxylating salicylate and its methyl- or chloro-substituted derivatives.
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Affiliation(s)
- Na Li
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Li Yao
- School of Marine and Biological Engineering, Yancheng Teachers University, Yancheng, Jiangsu, China
| | - Qin He
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Jiguo Qiu
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Dan Cheng
- Laboratory Centre of Life Science, College of Life Science, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Derong Ding
- Beijing DBN Biotech Co., Ltd., Beijing, China
| | - Qing Tao
- Beijing DBN Biotech Co., Ltd., Beijing, China
| | - Jian He
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, China
- Laboratory Centre of Life Science, College of Life Science, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Jiandong Jiang
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, China
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