The Experts below are selected from a list of 1950 Experts worldwide ranked by ideXlab platform
Benjamin Ricken - One of the best experts on this subject based on the ideXlab platform.
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fmnh2 dependent monooxygenases initiate catabolism of Sulfonamides in microbacterium sp strain br1 subsisting on Sulfonamide Antibiotics
Scientific Reports, 2017Co-Authors: Benjamin Ricken, Boris A Kolvenbach, Christian Bergesch, Kevin Kroll, Ricardo Adaixo, Hynek Strnad, Cestmir Vlcek, Dirk Benndorf, Frederik Hammes, Patrick ShahgaldianAbstract:We report a cluster of genes encoding two monooxygenases (SadA and SadB) and one FMN reductase (SadC) that enable Microbacterium sp. strain BR1 and other Actinomycetes to inactivate Sulfonamide Antibiotics. Our results show that SadA and SadC are responsible for the initial attack of Sulfonamide molecules resulting in the release of 4-aminophenol. The latter is further transformed into 1,2,4-trihydroxybenzene by SadB and SadC prior to mineralization and concomitant production of biomass. As the degradation products lack antibiotic activity, the presence of SadA will result in an alleviated bacteriostatic effect of Sulfonamides. In addition to the relief from antibiotic stress this bacterium gains access to an additional carbon source when this gene cluster is expressed. As degradation of Sulfonamides was also observed when Microbacterium sp. strain BR1 was grown on artificial urine medium, colonization with such strains may impede common Sulfonamide treatment during co-infections with pathogens of the urinary tract. This case of biodegradation exemplifies the evolving catabolic capacity of bacteria, given that Sulfonamide bacteriostatic are purely of synthetic origin. The wide distribution of this cluster in Actinomycetes and the presence of traA encoding a relaxase in its vicinity suggest that this cluster is mobile and that is rather alarming.
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Degradation of Sulfonamide Antibiotics by Microbacterium sp. strain BR1 – elucidating the downstream pathway
New biotechnology, 2015Co-Authors: Benjamin Ricken, Oliver Fellmann, Hans-peter E. Kohler, Andreas Schäffer, Philippe F.-x. Corvini, Boris A KolvenbachAbstract:Microbacterium sp. strain BR1 is among the first bacterial isolates which were proven to degrade Sulfonamide Antibiotics. The degradation is initiated by an ipso-substitution, initiating the decay of the molecule into sulfur dioxide, the substrate specific heterocyclic moiety as a stable metabolite and benzoquinone imine. The latter appears to be instantaneously reduced to p-aminophenol, as that in turn was detected as the first stable intermediate. This study investigated the downstream pathway of Sulfonamide Antibiotics by testing the strain's ability to degrade suspected intermediates of this pathway. While p-aminophenol was degraded, degradation products could not be identified. Benzoquinone was shown to be degraded to hydroquinone and hydroquinone in turn was shown to be degraded to 1,2,4-trihydroxybenzene. The latter is assumed to be the potential substrate for aromatic ring cleavage. However, no products from the degradation of 1,2,4-trihydroxybenzene could be identified. There are no signs of accumulation of intermediates causing oxidative stress, which makes Microbacterium sp. strain BR1 an interesting candidate for industrial waste water treatment.
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ipso-Hydroxylation and Subsequent Fragmentation: a Novel Microbial Strategy To Eliminate Sulfonamide Antibiotics
Applied and environmental microbiology, 2013Co-Authors: Benjamin Ricken, Patrick Shahgaldian, Philippe F.-x. Corvini, Danuta Cichocka, Martina Parisi, Markus Lenz, Dominik Wyss, Paula M. Martínez-lavanchy, Jochen A. Müller, Ludovico G. TulliAbstract:Sulfonamide Antibiotics have a wide application range in human and veterinary medicine. Because they tend to persist in the environment, they pose potential problems with regard to the propagation of antibiotic resistance. Here, we identified metabolites formed during the degradation of sulfamethoxazole and other Sulfonamides in Microbacterium sp. strain BR1. Our experiments showed that the degradation proceeded along an unusual pathway initiated by ipso-hydroxylation with subsequent fragmentation of the parent compound. The NADH-dependent hydroxylation of the carbon atom attached to the sulfonyl group resulted in the release of sulfite, 3-amino-5-methylisoxazole, and benzoquinone-imine. The latter was concomitantly transformed to 4-aminophenol. Sulfadiazine, sulfamethizole, sulfamethazine, sulfadimethoxine, 4-amino-N-phenylbenzeneSulfonamide, and N-(4-aminophenyl)sulfonylcarbamic acid methyl ester (asulam) were transformed accordingly. Therefore, ipso-hydroxylation with subsequent fragmentation must be considered the underlying mechanism; this could also occur in the same or in a similar way in other studies, where biotransformation of Sulfonamides bearing an amino group in the para-position to the sulfonyl substituent was observed to yield products corresponding to the stable metabolites observed by us.
Boris A Kolvenbach - One of the best experts on this subject based on the ideXlab platform.
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Biotransformation of Sulfonamide Antibiotics in Activated Sludge: The Formation of Pterin-Conjugates Leads to Sustained Risk.
Environmental science & technology, 2018Co-Authors: Stefan Achermann, Boris A Kolvenbach, Philippe F.-x. Corvini, Valeria Bianco, Cresten B. Mansfeldt, Bernadette Vogler, Kathrin FennerAbstract:The presence of Antibiotics in treated wastewater and consequently in surface and groundwater resources raises concerns about the formation and spread of antibiotic resistance. Improving the removal of Antibiotics during wastewater treatment therefore is a prime objective of environmental engineering. Here we obtained a detailed picture of the fate of Sulfonamide Antibiotics during activated sludge treatment using a combination of analytical methods. We show that pterin-Sulfonamide conjugates, which are formed when Sulfonamides interact with their target enzyme to inhibit folic acid synthesis, represent a major biotransformation route for Sulfonamides in laboratory batch experiments with activated sludge. The same major conjugates were also present in the effluents of nine Swiss wastewater treatment plants. The demonstration of this biotransformation route, which is related to bacterial growth, helps explain seemingly contradictory views on optimal conditions for Sulfonamide removal. More importantly, sin...
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Biotransformation of Sulfonamide Antibiotics in Activated Sludge: The Formation of Pterin-Conjugates Leads to Sustained Risk
2018Co-Authors: Stefan Achermann, Boris A Kolvenbach, Philippe F.-x. Corvini, Valeria Bianco, Cresten B. Mansfeldt, Bernadette Vogler, Kathrin FennerAbstract:The presence of Antibiotics in treated wastewater and consequently in surface and groundwater resources raises concerns about the formation and spread of antibiotic resistance. Improving the removal of Antibiotics during wastewater treatment therefore is a prime objective of environmental engineering. Here we obtained a detailed picture of the fate of Sulfonamide Antibiotics during activated sludge treatment using a combination of analytical methods. We show that pterin-Sulfonamide conjugates, which are formed when Sulfonamides interact with their target enzyme to inhibit folic acid synthesis, represent a major biotransformation route for Sulfonamides in laboratory batch experiments with activated sludge. The same major conjugates were also present in the effluents of nine Swiss wastewater treatment plants. The demonstration of this biotransformation route, which is related to bacterial growth, helps explain seemingly contradictory views on optimal conditions for Sulfonamide removal. More importantly, since pterin-Sulfonamide conjugates show retained antibiotic activity, our findings suggest that risk from exposure to Sulfonamide Antibiotics may be less reduced during wastewater treatment than previously assumed. Our results thus further emphasize the inadequacy of focusing on parent compound removal and the importance of investigating biotransformation pathways and removal of bioactivity to properly assess contaminant removal in both engineered and natural systems
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fmnh2 dependent monooxygenases initiate catabolism of Sulfonamides in microbacterium sp strain br1 subsisting on Sulfonamide Antibiotics
Scientific Reports, 2017Co-Authors: Benjamin Ricken, Boris A Kolvenbach, Christian Bergesch, Kevin Kroll, Ricardo Adaixo, Hynek Strnad, Cestmir Vlcek, Dirk Benndorf, Frederik Hammes, Patrick ShahgaldianAbstract:We report a cluster of genes encoding two monooxygenases (SadA and SadB) and one FMN reductase (SadC) that enable Microbacterium sp. strain BR1 and other Actinomycetes to inactivate Sulfonamide Antibiotics. Our results show that SadA and SadC are responsible for the initial attack of Sulfonamide molecules resulting in the release of 4-aminophenol. The latter is further transformed into 1,2,4-trihydroxybenzene by SadB and SadC prior to mineralization and concomitant production of biomass. As the degradation products lack antibiotic activity, the presence of SadA will result in an alleviated bacteriostatic effect of Sulfonamides. In addition to the relief from antibiotic stress this bacterium gains access to an additional carbon source when this gene cluster is expressed. As degradation of Sulfonamides was also observed when Microbacterium sp. strain BR1 was grown on artificial urine medium, colonization with such strains may impede common Sulfonamide treatment during co-infections with pathogens of the urinary tract. This case of biodegradation exemplifies the evolving catabolic capacity of bacteria, given that Sulfonamide bacteriostatic are purely of synthetic origin. The wide distribution of this cluster in Actinomycetes and the presence of traA encoding a relaxase in its vicinity suggest that this cluster is mobile and that is rather alarming.
-
Degradation of Sulfonamide Antibiotics by Microbacterium sp. strain BR1 – elucidating the downstream pathway
New biotechnology, 2015Co-Authors: Benjamin Ricken, Oliver Fellmann, Hans-peter E. Kohler, Andreas Schäffer, Philippe F.-x. Corvini, Boris A KolvenbachAbstract:Microbacterium sp. strain BR1 is among the first bacterial isolates which were proven to degrade Sulfonamide Antibiotics. The degradation is initiated by an ipso-substitution, initiating the decay of the molecule into sulfur dioxide, the substrate specific heterocyclic moiety as a stable metabolite and benzoquinone imine. The latter appears to be instantaneously reduced to p-aminophenol, as that in turn was detected as the first stable intermediate. This study investigated the downstream pathway of Sulfonamide Antibiotics by testing the strain's ability to degrade suspected intermediates of this pathway. While p-aminophenol was degraded, degradation products could not be identified. Benzoquinone was shown to be degraded to hydroquinone and hydroquinone in turn was shown to be degraded to 1,2,4-trihydroxybenzene. The latter is assumed to be the potential substrate for aromatic ring cleavage. However, no products from the degradation of 1,2,4-trihydroxybenzene could be identified. There are no signs of accumulation of intermediates causing oxidative stress, which makes Microbacterium sp. strain BR1 an interesting candidate for industrial waste water treatment.
Wenshan Guo - One of the best experts on this subject based on the ideXlab platform.
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improving Sulfonamide Antibiotics removal from swine wastewater by supplying a new pomelo peel derived biochar in an anaerobic membrane bioreactor
Bioresource Technology, 2021Co-Authors: Dongle Cheng, Huu Hao Ngo, Wenshan Guo, Soon Woong Chang, Dinh Duc Nguyen, Quynh Anh Nguyen, Jian Zhang, Shuang LiangAbstract:Abstract Sulfonamide Antibiotics (SMs), as a class of Antibiotics commonly used in swine industries, pose a serious threat to animal and human health. This study aims to evaluate the performance of an anaerobic membrane bioreactor (AnMBR) with and without supplying a new pomelo peel derived biochar to treat swine wastewater containing SMs. Results show that 0.5 g/L biochar addition could increase more than 30% of sulfadiazine (SDZ) and sulfamethazine (SMZ) removal in AnMBR. Approximately 95% of chemical oxygen demand (COD) was removed in the AnMBR at an influent organic loading rate (OLR) of 3.27 kg COD/(m3·d) while an average methane yield was 0.2 L/g CODremoved with slightly change at a small dose 0.5 g/L biochar addition. SMs inhibited the COD removal and methane production and increased membrane fouling. The addition of biochar could reduce the membrane fouling by reducing the concentration of SMP and EPS.
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Applying a new pomelo peel derived biochar in microbial fell cell for enhancing Sulfonamide Antibiotics removal in swine wastewater
Bioresource technology, 2020Co-Authors: Dongle Cheng, Huu Hao Ngo, Wenshan Guo, Soon Woong Chang, Dinh Duc Nguyen, Thi An Hang Nguyen, Van Son TranAbstract:Abstract A sequential anode-cathode double-chamber microbial fuel cell (MFC) is a promising system for simultaneously removing contaminants, recovering nutrients and producing energy from swine wastewater. To improve Sulfonamide Antibiotics (SMs)’s removal in the continuous operating of MFC, one new pomelo peel-derived biochar was applied in the anode chamber in this study. Results demonstrated that SMs can be absorbed onto the heterogeneous surfaces of biochar through pore-filling and π-π EDA interaction. Adding biochar to a certain concentration (500 mg/L) could enhance the efficiency in removing sulfamethoxazole, sulfadiazine and sulfamethazine to 82.44 - 88.15%, 53.40 - 77.53% and 61.12 - 80.68%, respectively. Moreover, electricity production, COD and nutrients removal were improved by increasing the concentration of biochar. Hence, it is proved that adding biochar in MFC could effectively improve the performance of MFC in treating swine wastewater containing SMs.
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Characterization and Sulfonamide Antibiotics adsorption capacity of spent coffee grounds based biochar and hydrochar
The Science of the total environment, 2020Co-Authors: Xinbo Zhang, Yongchao Zhang, Huu Hao Ngo, Wenshan Guo, Haitao Wen, Dan Zhang, Li ChaocanAbstract:Abstract A large amount of spent coffee grounds is produced as a processing waste each year during making the coffee beverage. Sulfonamide Antibiotics (SAs) are frequently detected in the environment and cause pollution problems. In this study, biochar (BC) and hydrochar (HC) were derived from spent coffee grounds through pyrolysis and hydrothermal carbonization, respectively. Their characteristics and Sulfonamide Antibiotics adsorption were investigated and compared with reference to adsorption capacity, adsorption isotherm and kinetics. Results showed BC possessed more carbonization and less oxygen-containing functional groups than HC when checked by Elemental Analysis, X-ray diffraction, X-ray photoelectron spectrometry and Fourier transform infrared. These groups affected the adsorption of Sulfonamide Antibiotics and adsorption mechanism. The maximum adsorption capacities of BC for sulfadiazine (SDZ) and sulfamethoxazole (SMX) were 121.5 μg/g and 130.1 μg/g at 25 °C with the initial antibiotic concentration of 500 μg/L, respectively. Meanwhile the maximum adsorption capacities of HC were 82.2 μg/g and 85.7 μg/g, respectively. Moreover, the adsorption mechanism for SAs adsorbed onto BC may be dominated by π-π electron donor-acceptor interactions, yet the SAs adsorption to HC may be attributed to hydrogen bonds. Further analysis of the adsorption isotherms and kinetics, found that physical and chemical interactions were involved in the SAs adsorption onto BC and HC. Overall, results suggested that: firstly, pyrolysis was an effective thermochemical conversion of spent coffee grounds; and secondly, BC was the more promising adsorbent for removing Sulfonamide Antibiotics.
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Removal and degradation mechanisms of Sulfonamide Antibiotics in a new integrated aerobic submerged membrane bioreactor system.
Bioresource technology, 2018Co-Authors: Yu Zhihao, Xinbo Zhang, Huu Hao Ngo, Wenshan Guo, Haitao Wen, Lijuan Deng, Jianbo GuoAbstract:Abstract A novel laboratory-scale aerobic submerged membrane bioreactor integrating sponge-plastic biocarriers (SPSMBR) was conducted to study the removal and degradation mechanisms of Sulfonamide Antibiotics (SAs). Experimental results indicated that SPSMBR had a better removal of sulfadiazine (91% SDZ) and sulfamethoxazole (88% SMZ) than that of a conventional aerobic submerged membrane bioreactor (CSMBR) (76% SDZ and 71% SMZ, respectively). Material balance calculations suggested that biodegradation is the primary removal mechanism of SDZ and SMZ. Protein (tyrosine-like materials) significantly affected the removal of SAs. Moreover, the SPSMBR exhibited its better performance in removing SAs due to more abundance of tyrosine-like materials. The 16S rRNA sequencing showed that biocarriers could promote the enrichment of slow growing bacteria, especially Thermomonas, associated with the removal of SAs. Valuable insights into the removal and degradation mechanisms of SAs in the SPSMBR systems are documented here.
Huu Hao Ngo - One of the best experts on this subject based on the ideXlab platform.
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improving Sulfonamide Antibiotics removal from swine wastewater by supplying a new pomelo peel derived biochar in an anaerobic membrane bioreactor
Bioresource Technology, 2021Co-Authors: Dongle Cheng, Huu Hao Ngo, Wenshan Guo, Soon Woong Chang, Dinh Duc Nguyen, Quynh Anh Nguyen, Jian Zhang, Shuang LiangAbstract:Abstract Sulfonamide Antibiotics (SMs), as a class of Antibiotics commonly used in swine industries, pose a serious threat to animal and human health. This study aims to evaluate the performance of an anaerobic membrane bioreactor (AnMBR) with and without supplying a new pomelo peel derived biochar to treat swine wastewater containing SMs. Results show that 0.5 g/L biochar addition could increase more than 30% of sulfadiazine (SDZ) and sulfamethazine (SMZ) removal in AnMBR. Approximately 95% of chemical oxygen demand (COD) was removed in the AnMBR at an influent organic loading rate (OLR) of 3.27 kg COD/(m3·d) while an average methane yield was 0.2 L/g CODremoved with slightly change at a small dose 0.5 g/L biochar addition. SMs inhibited the COD removal and methane production and increased membrane fouling. The addition of biochar could reduce the membrane fouling by reducing the concentration of SMP and EPS.
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Applying a new pomelo peel derived biochar in microbial fell cell for enhancing Sulfonamide Antibiotics removal in swine wastewater
Bioresource technology, 2020Co-Authors: Dongle Cheng, Huu Hao Ngo, Wenshan Guo, Soon Woong Chang, Dinh Duc Nguyen, Thi An Hang Nguyen, Van Son TranAbstract:Abstract A sequential anode-cathode double-chamber microbial fuel cell (MFC) is a promising system for simultaneously removing contaminants, recovering nutrients and producing energy from swine wastewater. To improve Sulfonamide Antibiotics (SMs)’s removal in the continuous operating of MFC, one new pomelo peel-derived biochar was applied in the anode chamber in this study. Results demonstrated that SMs can be absorbed onto the heterogeneous surfaces of biochar through pore-filling and π-π EDA interaction. Adding biochar to a certain concentration (500 mg/L) could enhance the efficiency in removing sulfamethoxazole, sulfadiazine and sulfamethazine to 82.44 - 88.15%, 53.40 - 77.53% and 61.12 - 80.68%, respectively. Moreover, electricity production, COD and nutrients removal were improved by increasing the concentration of biochar. Hence, it is proved that adding biochar in MFC could effectively improve the performance of MFC in treating swine wastewater containing SMs.
-
Characterization and Sulfonamide Antibiotics adsorption capacity of spent coffee grounds based biochar and hydrochar
The Science of the total environment, 2020Co-Authors: Xinbo Zhang, Yongchao Zhang, Huu Hao Ngo, Wenshan Guo, Haitao Wen, Dan Zhang, Li ChaocanAbstract:Abstract A large amount of spent coffee grounds is produced as a processing waste each year during making the coffee beverage. Sulfonamide Antibiotics (SAs) are frequently detected in the environment and cause pollution problems. In this study, biochar (BC) and hydrochar (HC) were derived from spent coffee grounds through pyrolysis and hydrothermal carbonization, respectively. Their characteristics and Sulfonamide Antibiotics adsorption were investigated and compared with reference to adsorption capacity, adsorption isotherm and kinetics. Results showed BC possessed more carbonization and less oxygen-containing functional groups than HC when checked by Elemental Analysis, X-ray diffraction, X-ray photoelectron spectrometry and Fourier transform infrared. These groups affected the adsorption of Sulfonamide Antibiotics and adsorption mechanism. The maximum adsorption capacities of BC for sulfadiazine (SDZ) and sulfamethoxazole (SMX) were 121.5 μg/g and 130.1 μg/g at 25 °C with the initial antibiotic concentration of 500 μg/L, respectively. Meanwhile the maximum adsorption capacities of HC were 82.2 μg/g and 85.7 μg/g, respectively. Moreover, the adsorption mechanism for SAs adsorbed onto BC may be dominated by π-π electron donor-acceptor interactions, yet the SAs adsorption to HC may be attributed to hydrogen bonds. Further analysis of the adsorption isotherms and kinetics, found that physical and chemical interactions were involved in the SAs adsorption onto BC and HC. Overall, results suggested that: firstly, pyrolysis was an effective thermochemical conversion of spent coffee grounds; and secondly, BC was the more promising adsorbent for removing Sulfonamide Antibiotics.
-
Removal and degradation mechanisms of Sulfonamide Antibiotics in a new integrated aerobic submerged membrane bioreactor system.
Bioresource technology, 2018Co-Authors: Yu Zhihao, Xinbo Zhang, Huu Hao Ngo, Wenshan Guo, Haitao Wen, Lijuan Deng, Jianbo GuoAbstract:Abstract A novel laboratory-scale aerobic submerged membrane bioreactor integrating sponge-plastic biocarriers (SPSMBR) was conducted to study the removal and degradation mechanisms of Sulfonamide Antibiotics (SAs). Experimental results indicated that SPSMBR had a better removal of sulfadiazine (91% SDZ) and sulfamethoxazole (88% SMZ) than that of a conventional aerobic submerged membrane bioreactor (CSMBR) (76% SDZ and 71% SMZ, respectively). Material balance calculations suggested that biodegradation is the primary removal mechanism of SDZ and SMZ. Protein (tyrosine-like materials) significantly affected the removal of SAs. Moreover, the SPSMBR exhibited its better performance in removing SAs due to more abundance of tyrosine-like materials. The 16S rRNA sequencing showed that biocarriers could promote the enrichment of slow growing bacteria, especially Thermomonas, associated with the removal of SAs. Valuable insights into the removal and degradation mechanisms of SAs in the SPSMBR systems are documented here.
Patrick Shahgaldian - One of the best experts on this subject based on the ideXlab platform.
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fmnh2 dependent monooxygenases initiate catabolism of Sulfonamides in microbacterium sp strain br1 subsisting on Sulfonamide Antibiotics
Scientific Reports, 2017Co-Authors: Benjamin Ricken, Boris A Kolvenbach, Christian Bergesch, Kevin Kroll, Ricardo Adaixo, Hynek Strnad, Cestmir Vlcek, Dirk Benndorf, Frederik Hammes, Patrick ShahgaldianAbstract:We report a cluster of genes encoding two monooxygenases (SadA and SadB) and one FMN reductase (SadC) that enable Microbacterium sp. strain BR1 and other Actinomycetes to inactivate Sulfonamide Antibiotics. Our results show that SadA and SadC are responsible for the initial attack of Sulfonamide molecules resulting in the release of 4-aminophenol. The latter is further transformed into 1,2,4-trihydroxybenzene by SadB and SadC prior to mineralization and concomitant production of biomass. As the degradation products lack antibiotic activity, the presence of SadA will result in an alleviated bacteriostatic effect of Sulfonamides. In addition to the relief from antibiotic stress this bacterium gains access to an additional carbon source when this gene cluster is expressed. As degradation of Sulfonamides was also observed when Microbacterium sp. strain BR1 was grown on artificial urine medium, colonization with such strains may impede common Sulfonamide treatment during co-infections with pathogens of the urinary tract. This case of biodegradation exemplifies the evolving catabolic capacity of bacteria, given that Sulfonamide bacteriostatic are purely of synthetic origin. The wide distribution of this cluster in Actinomycetes and the presence of traA encoding a relaxase in its vicinity suggest that this cluster is mobile and that is rather alarming.
-
ipso-Hydroxylation and Subsequent Fragmentation: a Novel Microbial Strategy To Eliminate Sulfonamide Antibiotics
Applied and environmental microbiology, 2013Co-Authors: Benjamin Ricken, Patrick Shahgaldian, Philippe F.-x. Corvini, Danuta Cichocka, Martina Parisi, Markus Lenz, Dominik Wyss, Paula M. Martínez-lavanchy, Jochen A. Müller, Ludovico G. TulliAbstract:Sulfonamide Antibiotics have a wide application range in human and veterinary medicine. Because they tend to persist in the environment, they pose potential problems with regard to the propagation of antibiotic resistance. Here, we identified metabolites formed during the degradation of sulfamethoxazole and other Sulfonamides in Microbacterium sp. strain BR1. Our experiments showed that the degradation proceeded along an unusual pathway initiated by ipso-hydroxylation with subsequent fragmentation of the parent compound. The NADH-dependent hydroxylation of the carbon atom attached to the sulfonyl group resulted in the release of sulfite, 3-amino-5-methylisoxazole, and benzoquinone-imine. The latter was concomitantly transformed to 4-aminophenol. Sulfadiazine, sulfamethizole, sulfamethazine, sulfadimethoxine, 4-amino-N-phenylbenzeneSulfonamide, and N-(4-aminophenyl)sulfonylcarbamic acid methyl ester (asulam) were transformed accordingly. Therefore, ipso-hydroxylation with subsequent fragmentation must be considered the underlying mechanism; this could also occur in the same or in a similar way in other studies, where biotransformation of Sulfonamides bearing an amino group in the para-position to the sulfonyl substituent was observed to yield products corresponding to the stable metabolites observed by us.
