In Vietnam&am... more In Vietnam's coastal wetlands, fluoroquinolones, a widely used class of antibiotics in shrimp farming, are frequently detected in sediments of former shrimp farms. This phenomenon could lead to negative impacts on the aquatic ecosystem, since the antibiotic residues could induce changes in the microorganism communities of the water body. The potential of native wetland plants (Acrostichum aureum L. and Rhizophora apiculata Blume Fl. Javae) for phytoremediation of fluoroquinolones (ciprofloxacin and norfloxacin) was investigated. The half-life for each antibiotic was estimated at approximately 10 days in the planted sediment. With respect to the accumulation of ciprofloxacin and norfloxacin in plants, these antibiotics were found mainly in roots. Antibiotic translocation from root to stem and leaves occurred at a low rate. The results showed that A. aureum and R. apiculata can be valuable for the phytoremediation of antibiotic-contaminated sediments. Additionally, the initialfindings of the presence of resistant bacteria indicated that bacteria could play a role in facilitating the phytodegradation.
... Lê Phi Nga (1), Nguyễn Thị Thư Hiền (1), Nguyễn Thị Hoa Liên (1), Dương Thị Hương Giang (2), ... more ... Lê Phi Nga (1), Nguyễn Thị Thư Hiền (1), Nguyễn Thị Hoa Liên (1), Dương Thị Hương Giang (2), Đinh ... suất thu protein ty thể đạt trong khoảng 1-1,4% trọng lượng tim bò tươi (đã loại bỏ ... Nước thải công nghiệp (% v/v) T03.57-1/4 (da giày) 0,266-0,375 0,081-1,136 0,68 1,587 ...
ABSTRACT Vietnamese coastal wetlands have traditionally been used for shrimp farming, but with th... more ABSTRACT Vietnamese coastal wetlands have traditionally been used for shrimp farming, but with the expansion of commercial shrimp farming and the associated clearance of mangroves, these valuable ecosystems have been rapidly degraded. The application of veterinary antibiotics in shrimp culture is one of the major threats to Vietnamese mangroves. These antibiotics are released into the environment through wastewater streams from shrimp ponds and cause environmental problems as well as the occurrence of antibiotic resistant bacteria. However, there is only a limited amount of information available on the occurrence and fate of antibiotics in Vietnamese mangroves. Ciprofloxacin and norfloxacin are two of most commonly fluoroquinolones used in shrimp culture. Laboratory experiments were therefore carried out using saline shrimp pond water to investigate the fate of both antibiotics in a coastal wetland ecosystem. Furthermore, two wetland plant species (Ceratophyllum demersum and Chrysopogon zizanioides), were used for studying phytoremediation of both antibiotics through a hydroponic experiment. Both ciprofloxacin and norfloxacin were photodegradable but at a slow rate, whereas the biodegradation seemed to be insignificant. If given at an initial concentration of 5 or 10 mg/L, a higher removal of antibiotics was achieved using C. demersum: 40 % for norfloxacin and 44–39 % for ciprofloxacin, respectively. With C. zizanioides, ciprofloxacin and norfloxacin were reduced by 40–38 and 36–34 %, respectively. These results indicated that phytoremediation could be effective in the removal of both antibiotics.
Sequencing of a cadmium resistance operon from a Staphylococcus aureus ATCC12600 plasmid revealed... more Sequencing of a cadmium resistance operon from a Staphylococcus aureus ATCC12600 plasmid revealed that it is identical to a cadCA operon found in MRSA strains. Compared to plasmid-cured and cadC-mutant strains, cadC-positive ATCC12600 cells had increased resistance to cadmium (1 mg ml(-1) cadmium sulfate) and zinc (4 mg ml(-1) zinc sulfate), but not to other metal ions. After growth in media containing 20 µg ml(-1) cadmium sulfate, cadC-mutant cells contained more intracellular cadmium than cadC-positive ATCC12600 cells, suggesting that cadC absence results in impaired cadmium efflux. Electrophoretic mobility shift assays were performed with CadC proteins encoded by the S. aureus ATCC12600 plasmid and by the cadC gene of pI258, which is known to act as a transcriptional repressor and shares only 47% protein sequence identity with ATCC12600 CadC. Mobility shifts occurred when pI258 CadC protein was incubated with the promoter DNA-regions from the pI258 and S. aureus ATCC12600 cadCA operons, but did not occur with S. aureus ATCC12600 CadC protein, indicating that the ATCC12600 CadC protein does not interact with promoter region DNA. This cadCA operon, found in MRSA strains and previously functionally uncharacterized, increases resistance to cadmium and zinc by an efflux mechanism, and CadC does not function as a transcriptional repressor.
The FOF1 ATP synthase uses a unique rotational mechanism to couple energy from the translocation ... more The FOF1 ATP synthase uses a unique rotational mechanism to couple energy from the translocation of protons across the membrane to the synthesis of ATP from ADP and Pi. The movement of the rotor complex is integral to both catalysis and transport, and both mechanisms are ...
Molecular tools for Gram-positive bacteria such as Mycobacterium are less well-developed than tho... more Molecular tools for Gram-positive bacteria such as Mycobacterium are less well-developed than those for Gram-negatives such as Escherichiacoli. This has slowed the molecular-genetic characterisation of Mycobacterium spp, which is unfortunate, since this genus has high medical, environmental and industrial significance. Here, we developed a new Mycobacterium shuttle vector (pMycoFos, 12.5kb, KmR) which combines desirable features of several previous vectors (controllable
Polyelectrolytes are used in drinking water treatment and potentially remain as contaminants in t... more Polyelectrolytes are used in drinking water treatment and potentially remain as contaminants in the treated water. A method capable of quantifying these polymers at concentrations well below 1 mg/L is needed. Copolymerization of acrylamide or DADMAC with small amounts of an amine-functional monomer yields a flocculant that can be tagged with a reactive fluorophore before or after use and detected
Journal of the American Chemical Society, Jan 28, 2009
The reduction of a redox-active ligand is shown to drive reversible switching of a Cu(I) [2]pseud... more The reduction of a redox-active ligand is shown to drive reversible switching of a Cu(I) [2]pseudorotaxane ([2]PR(+)) into the reduced [3]pseudorotaxane ([3]PR(+)) by a bimolecular mechanism. The unreduced pseudorotaxanes [2]PR(+) and [3]PR(2+) are initially self-assembled from the binucleating ligand, 3,6-bis(5-methyl-2-pyridine)-1,2,4,5-tetrazine (Me(2)BPTZ), and a preformed copper-macrocycle moiety (Cu-M(+)) based on 1,10-phenanthroline. X-ray crystallography revealed a syn geometry of the [3]PR(2+). The UV-vis-NIR spectra show low-energy metal-to-ligand charge-transfer transitions that red shift from 808 nm for [2]PR(+) to 1088 nm for [3]PR(2+). Quantitative analysis of the UV-vis-NIR titration shows the stepwise formation constants to be K(1) = 8.9 x 10(8) M(-1) and K(2) = 3.1 x 10(6) M(-1), indicative of negative cooperativity. The cyclic voltammetry (CV) and coulometry of Me(2)BPTZ, [2]PR(+), and [3]PR(2+) shows the one-electron reductions at E(1/2) = -0.96, -0.65, and -0.285...
Mycobacterium chubuense strain NBB4 can grow on both alkanes and alkenes as carbon sources, and w... more Mycobacterium chubuense strain NBB4 can grow on both alkanes and alkenes as carbon sources, and was hypothesised to be an effective bioremediation agent for chlorinated aliphatic pollutants. In this study, the ability of NBB4 to biodegrade vinyl chloride (VC), cis-dichloroethene (cDCE) and 1,2-dichloroethane (DCA) was investigated under pure-culture conditions and in microcosms. Ethenegrown NBB4 cells were capable of biodegrading VC and cDCE, while ethane-grown cells could biodegrade cDCE and DCA. The stoichiometry of inorganic chloride release (1 mol/mol in each case) indicated that VC was completely dechlorinated, while cDCE and DCA were only partially dechlorinated, yielding chloroacetate in the case of DCA, and unknown metabolites in the case of cDCE. The apparent maximum specific activities (k) of whole cells against ethene, cDCE, ethane and DCA were 93 ± 4.6, 89 ± 18, 39 ± 5.5, and 4.8 ± 0.9 nmol/ min/mg protein, respectively, while the substrate affinities (K S ) of whole cells with the same substrates were 2.0 ± 0.15, 46 ± 11, 11 ± 0.33 and 4.0 ± 3.2 lM, respectively. In microcosms containing contaminated aquifer sediments and groundwater, NBB4 cells removed 85-95% of the pollutants (cDCE or DCA at 2 mM) within 24 h, and the cells remained viable for [1 month. Due to its favourable kinetic parameters, and robust survival and biodegradation activities, strain NBB4 is a promising candidate for bioremediation of chlorinated aliphatic pollutants.
Steady-state ATP hydrolysis in the F1-ATPase of the F(O)F1 ATP synthase complex involves rotation... more Steady-state ATP hydrolysis in the F1-ATPase of the F(O)F1 ATP synthase complex involves rotation of the central gamma subunit relative to the catalytic sites in the alpha3beta3 pseudo-hexamer. To understand the relationship between the catalytic mechanism and gamma subunit rotation, the pre-steady-state kinetics of Mg x ATP hydrolysis in the soluble F1-ATPase upon rapid filling of all three catalytic sites was determined. The experimentally accessible partial reactions leading up to the rate-limiting step and continuing through to the steady-state mode were obtained for the first time. The burst kinetics and steady-state hydrolysis for a range of Mg x ATP concentrations provide adequate constraints for a unique minimal kinetic model that can fit all the data and satisfy extensive sensitivity tests. Significantly, the fits show that the ratio of the rates of ATP hydrolysis and synthesis is close to unity even in the steady-state mode of hydrolysis. Furthermore, the rate of Pi binding in the absence of the membranous F(O) sector is insignificant; thus, productive Pi binding does not occur without the influence of a proton motive force. In addition to the minimal steps of ATP binding, reversible ATP hydrolysis/synthesis, and the release of product Pi and ADP, one additional rate-limiting step is required to fit the burst kinetics. On the basis of the testing of all possible minimal kinetic models, this step must follow hydrolysis and precede Pi release in order to explain burst kinetics. Consistent with the single molecule analysis of Yasuda et al. (Yasuda, R., Noji, H., Yoshida, M., Kinosita, K., and Itoh, H. (2001) Nature 410, 898-904), we propose that the rate-limiting step involves a partial rotation of the gamma subunit; hence, we name this step k(gamma). Moreover, the only model that is consistent with our data and many other observations in the literature suggests that reversible hydrolysis/synthesis can only occur in the active site of the beta(TP) conformer (Abrahams, J. P., Leslie, A. G. W., Lutter, R., and Walker, J. E. (1994) Nature 370, 621-628).
The copper membrane monooxygenases (CuMMOs) are an important group of enzymes in environmental sc... more The copper membrane monooxygenases (CuMMOs) are an important group of enzymes in environmental science and biotechnology. Areas of relevance include the development of green chemistry for sustainable exploitation of methane (CH4) reserves, remediation of chlorinated hydrocarbon contamination and monitoring human impact in the biogeochemical cycles of CH4 and nitrogen. Challenges for all these applications are that many aspects of the
In Vietnam&am... more In Vietnam's coastal wetlands, fluoroquinolones, a widely used class of antibiotics in shrimp farming, are frequently detected in sediments of former shrimp farms. This phenomenon could lead to negative impacts on the aquatic ecosystem, since the antibiotic residues could induce changes in the microorganism communities of the water body. The potential of native wetland plants (Acrostichum aureum L. and Rhizophora apiculata Blume Fl. Javae) for phytoremediation of fluoroquinolones (ciprofloxacin and norfloxacin) was investigated. The half-life for each antibiotic was estimated at approximately 10 days in the planted sediment. With respect to the accumulation of ciprofloxacin and norfloxacin in plants, these antibiotics were found mainly in roots. Antibiotic translocation from root to stem and leaves occurred at a low rate. The results showed that A. aureum and R. apiculata can be valuable for the phytoremediation of antibiotic-contaminated sediments. Additionally, the initialfindings of the presence of resistant bacteria indicated that bacteria could play a role in facilitating the phytodegradation.
... Lê Phi Nga (1), Nguyễn Thị Thư Hiền (1), Nguyễn Thị Hoa Liên (1), Dương Thị Hương Giang (2), ... more ... Lê Phi Nga (1), Nguyễn Thị Thư Hiền (1), Nguyễn Thị Hoa Liên (1), Dương Thị Hương Giang (2), Đinh ... suất thu protein ty thể đạt trong khoảng 1-1,4% trọng lượng tim bò tươi (đã loại bỏ ... Nước thải công nghiệp (% v/v) T03.57-1/4 (da giày) 0,266-0,375 0,081-1,136 0,68 1,587 ...
ABSTRACT Vietnamese coastal wetlands have traditionally been used for shrimp farming, but with th... more ABSTRACT Vietnamese coastal wetlands have traditionally been used for shrimp farming, but with the expansion of commercial shrimp farming and the associated clearance of mangroves, these valuable ecosystems have been rapidly degraded. The application of veterinary antibiotics in shrimp culture is one of the major threats to Vietnamese mangroves. These antibiotics are released into the environment through wastewater streams from shrimp ponds and cause environmental problems as well as the occurrence of antibiotic resistant bacteria. However, there is only a limited amount of information available on the occurrence and fate of antibiotics in Vietnamese mangroves. Ciprofloxacin and norfloxacin are two of most commonly fluoroquinolones used in shrimp culture. Laboratory experiments were therefore carried out using saline shrimp pond water to investigate the fate of both antibiotics in a coastal wetland ecosystem. Furthermore, two wetland plant species (Ceratophyllum demersum and Chrysopogon zizanioides), were used for studying phytoremediation of both antibiotics through a hydroponic experiment. Both ciprofloxacin and norfloxacin were photodegradable but at a slow rate, whereas the biodegradation seemed to be insignificant. If given at an initial concentration of 5 or 10 mg/L, a higher removal of antibiotics was achieved using C. demersum: 40 % for norfloxacin and 44–39 % for ciprofloxacin, respectively. With C. zizanioides, ciprofloxacin and norfloxacin were reduced by 40–38 and 36–34 %, respectively. These results indicated that phytoremediation could be effective in the removal of both antibiotics.
Sequencing of a cadmium resistance operon from a Staphylococcus aureus ATCC12600 plasmid revealed... more Sequencing of a cadmium resistance operon from a Staphylococcus aureus ATCC12600 plasmid revealed that it is identical to a cadCA operon found in MRSA strains. Compared to plasmid-cured and cadC-mutant strains, cadC-positive ATCC12600 cells had increased resistance to cadmium (1 mg ml(-1) cadmium sulfate) and zinc (4 mg ml(-1) zinc sulfate), but not to other metal ions. After growth in media containing 20 µg ml(-1) cadmium sulfate, cadC-mutant cells contained more intracellular cadmium than cadC-positive ATCC12600 cells, suggesting that cadC absence results in impaired cadmium efflux. Electrophoretic mobility shift assays were performed with CadC proteins encoded by the S. aureus ATCC12600 plasmid and by the cadC gene of pI258, which is known to act as a transcriptional repressor and shares only 47% protein sequence identity with ATCC12600 CadC. Mobility shifts occurred when pI258 CadC protein was incubated with the promoter DNA-regions from the pI258 and S. aureus ATCC12600 cadCA operons, but did not occur with S. aureus ATCC12600 CadC protein, indicating that the ATCC12600 CadC protein does not interact with promoter region DNA. This cadCA operon, found in MRSA strains and previously functionally uncharacterized, increases resistance to cadmium and zinc by an efflux mechanism, and CadC does not function as a transcriptional repressor.
The FOF1 ATP synthase uses a unique rotational mechanism to couple energy from the translocation ... more The FOF1 ATP synthase uses a unique rotational mechanism to couple energy from the translocation of protons across the membrane to the synthesis of ATP from ADP and Pi. The movement of the rotor complex is integral to both catalysis and transport, and both mechanisms are ...
Molecular tools for Gram-positive bacteria such as Mycobacterium are less well-developed than tho... more Molecular tools for Gram-positive bacteria such as Mycobacterium are less well-developed than those for Gram-negatives such as Escherichiacoli. This has slowed the molecular-genetic characterisation of Mycobacterium spp, which is unfortunate, since this genus has high medical, environmental and industrial significance. Here, we developed a new Mycobacterium shuttle vector (pMycoFos, 12.5kb, KmR) which combines desirable features of several previous vectors (controllable
Polyelectrolytes are used in drinking water treatment and potentially remain as contaminants in t... more Polyelectrolytes are used in drinking water treatment and potentially remain as contaminants in the treated water. A method capable of quantifying these polymers at concentrations well below 1 mg/L is needed. Copolymerization of acrylamide or DADMAC with small amounts of an amine-functional monomer yields a flocculant that can be tagged with a reactive fluorophore before or after use and detected
Journal of the American Chemical Society, Jan 28, 2009
The reduction of a redox-active ligand is shown to drive reversible switching of a Cu(I) [2]pseud... more The reduction of a redox-active ligand is shown to drive reversible switching of a Cu(I) [2]pseudorotaxane ([2]PR(+)) into the reduced [3]pseudorotaxane ([3]PR(+)) by a bimolecular mechanism. The unreduced pseudorotaxanes [2]PR(+) and [3]PR(2+) are initially self-assembled from the binucleating ligand, 3,6-bis(5-methyl-2-pyridine)-1,2,4,5-tetrazine (Me(2)BPTZ), and a preformed copper-macrocycle moiety (Cu-M(+)) based on 1,10-phenanthroline. X-ray crystallography revealed a syn geometry of the [3]PR(2+). The UV-vis-NIR spectra show low-energy metal-to-ligand charge-transfer transitions that red shift from 808 nm for [2]PR(+) to 1088 nm for [3]PR(2+). Quantitative analysis of the UV-vis-NIR titration shows the stepwise formation constants to be K(1) = 8.9 x 10(8) M(-1) and K(2) = 3.1 x 10(6) M(-1), indicative of negative cooperativity. The cyclic voltammetry (CV) and coulometry of Me(2)BPTZ, [2]PR(+), and [3]PR(2+) shows the one-electron reductions at E(1/2) = -0.96, -0.65, and -0.285...
Mycobacterium chubuense strain NBB4 can grow on both alkanes and alkenes as carbon sources, and w... more Mycobacterium chubuense strain NBB4 can grow on both alkanes and alkenes as carbon sources, and was hypothesised to be an effective bioremediation agent for chlorinated aliphatic pollutants. In this study, the ability of NBB4 to biodegrade vinyl chloride (VC), cis-dichloroethene (cDCE) and 1,2-dichloroethane (DCA) was investigated under pure-culture conditions and in microcosms. Ethenegrown NBB4 cells were capable of biodegrading VC and cDCE, while ethane-grown cells could biodegrade cDCE and DCA. The stoichiometry of inorganic chloride release (1 mol/mol in each case) indicated that VC was completely dechlorinated, while cDCE and DCA were only partially dechlorinated, yielding chloroacetate in the case of DCA, and unknown metabolites in the case of cDCE. The apparent maximum specific activities (k) of whole cells against ethene, cDCE, ethane and DCA were 93 ± 4.6, 89 ± 18, 39 ± 5.5, and 4.8 ± 0.9 nmol/ min/mg protein, respectively, while the substrate affinities (K S ) of whole cells with the same substrates were 2.0 ± 0.15, 46 ± 11, 11 ± 0.33 and 4.0 ± 3.2 lM, respectively. In microcosms containing contaminated aquifer sediments and groundwater, NBB4 cells removed 85-95% of the pollutants (cDCE or DCA at 2 mM) within 24 h, and the cells remained viable for [1 month. Due to its favourable kinetic parameters, and robust survival and biodegradation activities, strain NBB4 is a promising candidate for bioremediation of chlorinated aliphatic pollutants.
Steady-state ATP hydrolysis in the F1-ATPase of the F(O)F1 ATP synthase complex involves rotation... more Steady-state ATP hydrolysis in the F1-ATPase of the F(O)F1 ATP synthase complex involves rotation of the central gamma subunit relative to the catalytic sites in the alpha3beta3 pseudo-hexamer. To understand the relationship between the catalytic mechanism and gamma subunit rotation, the pre-steady-state kinetics of Mg x ATP hydrolysis in the soluble F1-ATPase upon rapid filling of all three catalytic sites was determined. The experimentally accessible partial reactions leading up to the rate-limiting step and continuing through to the steady-state mode were obtained for the first time. The burst kinetics and steady-state hydrolysis for a range of Mg x ATP concentrations provide adequate constraints for a unique minimal kinetic model that can fit all the data and satisfy extensive sensitivity tests. Significantly, the fits show that the ratio of the rates of ATP hydrolysis and synthesis is close to unity even in the steady-state mode of hydrolysis. Furthermore, the rate of Pi binding in the absence of the membranous F(O) sector is insignificant; thus, productive Pi binding does not occur without the influence of a proton motive force. In addition to the minimal steps of ATP binding, reversible ATP hydrolysis/synthesis, and the release of product Pi and ADP, one additional rate-limiting step is required to fit the burst kinetics. On the basis of the testing of all possible minimal kinetic models, this step must follow hydrolysis and precede Pi release in order to explain burst kinetics. Consistent with the single molecule analysis of Yasuda et al. (Yasuda, R., Noji, H., Yoshida, M., Kinosita, K., and Itoh, H. (2001) Nature 410, 898-904), we propose that the rate-limiting step involves a partial rotation of the gamma subunit; hence, we name this step k(gamma). Moreover, the only model that is consistent with our data and many other observations in the literature suggests that reversible hydrolysis/synthesis can only occur in the active site of the beta(TP) conformer (Abrahams, J. P., Leslie, A. G. W., Lutter, R., and Walker, J. E. (1994) Nature 370, 621-628).
The copper membrane monooxygenases (CuMMOs) are an important group of enzymes in environmental sc... more The copper membrane monooxygenases (CuMMOs) are an important group of enzymes in environmental science and biotechnology. Areas of relevance include the development of green chemistry for sustainable exploitation of methane (CH4) reserves, remediation of chlorinated hydrocarbon contamination and monitoring human impact in the biogeochemical cycles of CH4 and nitrogen. Challenges for all these applications are that many aspects of the
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