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1.
Artigo em Inglês | MEDLINE | ID: mdl-31434344

RESUMO

Despite the adverse effects of emerging ZnO nanoparticles (nano-ZnO) on wastewater biological nitrogen removal (BNR) systems being widely documented, strategies for mitigating nanoparticle (NP) toxicity impacts on nitrogen removal have not been adequately addressed. Herein, N-acyl-homoserine lactone (AHL)-based quorum sensing (QS) was investigated for its effects against nano-ZnO toxicity to a model nitrifier, Nitrosomonas europaea. The results indicated that AHL-attenuated nano-ZnO toxicity, which was inversely correlated with the increasing dosage of AHL from 0.01 to 1 µM. At 0.01 µM, AHL notably enhanced the tolerance of N. europaea cells to nano-ZnO stress, and the inhibited cell proliferation, membrane integrity, ammonia oxidation rate, ammonia monooxygenase activity and amoA gene expression significantly increased by 18.2 ± 2.1, 2.4 ± 0.9, 58.7 ± 7.1, 32.3 ± 1.7, and 7.3 ± 5.9%, respectively, after 6 h of incubation. However, increasing the AHL dosage compromised the QS-mediated effects and even aggravated the NPs' toxicity effects. Moreover, AHLs, at all tested concentrations, significantly increased superoxide dismutase activity, indicating the potential of QS regulations to enhance cellular anti-oxidative stress capacities when facing NP invasion. These results provide novel insights into the development of QS regulation strategies to reduce the impact of nanotoxicity on BNR systems.


Assuntos
4-Butirolactona/análogos & derivados , Nanopartículas Metálicas/química , Nitrosomonas europaea/efeitos dos fármacos , Transdução de Sinais , Óxido de Zinco/química , 4-Butirolactona/farmacologia , Nitrosomonas europaea/metabolismo , Oxirredução , Percepção de Quorum
2.
Bull Environ Contam Toxicol ; 103(1): 181-186, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31049596

RESUMO

Silver nanoparticles (AgNPs) is widely used as an antibacterial agent, but the specific antibacterial mechanism is still conflicting. This study aimed to investigate the size dependent inhibition of AgNPs and the relationship between inhibition and reactive oxygen species (ROS). Azotobactervinelandii and Nitrosomonaseuropaea were exposed to AgNPs with different particles size (10 nm and 50 nm). The ROS production was measured and the results showed that the generation of ROS related to the particle size and concentrations of AgNPs. At 10 mg/L of 10 nm Ag particles, the apoptosis rate of A. vinelandii and N. europaea were 20.23% and 1.87% respectively. Additionally, the necrosis rate of A. vinelandii and N. europaea reached to 15.20% and 42.20% respectively. Furthermore, transmission electron microscopy images also indicated that AgNPs caused severely bacterial cell membrane damage. Together these data suggested that the toxicity of AgNPs depends on its particle size and overproduction of ROS.


Assuntos
Azotobacter vinelandii/efeitos dos fármacos , Nanopartículas Metálicas/toxicidade , Nitrosomonas europaea/efeitos dos fármacos , Prata/toxicidade , Apoptose/efeitos dos fármacos , Microscopia Eletrônica de Transmissão , Tamanho da Partícula , Espécies Reativas de Oxigênio/metabolismo
3.
Appl Microbiol Biotechnol ; 101(7): 2953-2965, 2017 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28074222

RESUMO

The ZnO nanoparticle (NP) effects on typical ammonia-oxidizing bacteria, Nitrosomonas europaea in a chemostat bioreactor, and the cells' toxicity adaptation and recovery potentials were explored. Hardly any inhibition was observed when the NP concentration was high up to 10 mg/L. The cells exposed to 50 mg/L ZnO NPs displayed time-dependent impairment and recovery potentials in terms of cell density, membrane integrity, nitrite production rate, and ammonia monooxygenase activity. The 6-h NP stress impaired cells were nearly completely restored during a 12-h recovery incubation, while the longer exposure time would cause irretrievable cell damage. Microarray analysis further indicated the transcriptional adaptation of N. europaea to NP stress. The regulations of genes encoding for membrane permeability or osmoprotectant, membrane integrity preservation, and inorganic ion transport during NP exposure and cell recovery revealed the importance of membrane fixation and the associated metabolisms for cells' self-protection and the following recovery from NP stress. The oxidative phosphorylation, carbon assimilation, and tricarboxylic acid (TCA) cycling pathways involved in the cells' antitoxicity activities and would promote the energy production/conversion efficiency for cell recovery. The heavy metal resistance, histidine metabolism, toxin-antitoxin defense, glycolysis, and sulfate reduction pathways were also suggested to participate in the cell detoxication and recovery processes. All these findings provided valuable insights into the mechanisms of cell-mediated ZnO NP cytotoxicity and their potential impacts on wastewater nitrogen removal system.


Assuntos
Adaptação Fisiológica , Metabolismo Energético , Regulação Bacteriana da Expressão Gênica , Nanopartículas , Nitrosomonas europaea/efeitos dos fármacos , Nitrosomonas europaea/metabolismo , Óxido de Zinco/farmacologia , Aclimatação , Adaptação Fisiológica/efeitos dos fármacos , Adaptação Fisiológica/genética , Amônia/metabolismo , Reatores Biológicos , Carbono/metabolismo , Glicólise , Redes e Vias Metabólicas/genética , Análise em Microsséries , Nitritos/metabolismo , Nitrogênio/metabolismo , Nitrosomonas europaea/genética , Nitrosomonas europaea/crescimento & desenvolvimento , Oxirredução , Oxirredutases/metabolismo , Oxigênio/metabolismo , Óxido de Zinco/metabolismo
4.
FEMS Microbiol Lett ; 363(7)2016 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-26946536

RESUMO

Differential inhibitors are important for measuring the relative contributions of microbial groups, such as ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA), to biogeochemical processes in environmental samples. In particular, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO) represents a nitric oxide scavenger used for the specific inhibition of AOA, implicating nitric oxide as an intermediate of thaumarchaeotal ammonia oxidation. This study investigated four alternative nitric oxide scavengers for their ability to differentially inhibit AOA and AOB in comparison to PTIO. Caffeic acid, curcumin, methylene blue hydrate and trolox were tested onNitrosopumilus maritimus, two unpublished AOA representatives (AOA-6f and AOA-G6) as well as the AOB representative Nitrosomonas europaea All four scavengers inhibited ammonia oxidation by AOA at lower concentrations than for AOB. In particular, differential inhibition of AOA and AOB by caffeic acid (100 µM) and methylene blue hydrate (3 µM) was comparable to carboxy-PTIO (100 µM) in pure and enrichment culture incubations. However, when added to aquarium sponge biofilm microcosms, both scavengers were unable to inhibit ammonia oxidation consistently, likely due to degradation of the inhibitors themselves. This study provides evidence that a variety of nitric oxide scavengers result in differential inhibition of ammonia oxidation in AOA and AOB, and provides support to the proposed role of nitric oxide as a key intermediate in the thaumarchaeotal ammonia oxidation pathway.


Assuntos
Amônia/metabolismo , Archaea/efeitos dos fármacos , Archaea/metabolismo , Bactérias/efeitos dos fármacos , Bactérias/metabolismo , Óxido Nítrico/metabolismo , Microbiologia do Solo , Amônia/antagonistas & inibidores , Benzenossulfonatos/farmacologia , Benzoatos/farmacologia , Betaproteobacteria/efeitos dos fármacos , Betaproteobacteria/metabolismo , Ácidos Cafeicos/farmacologia , Cromanos/farmacologia , Curcumina/farmacologia , Imidazóis/farmacologia , Nitrificação , Nitrosomonas europaea/efeitos dos fármacos , Nitrosomonas europaea/metabolismo , Oxirredução/efeitos dos fármacos , Filogenia
5.
Chemosphere ; 153: 187-97, 2016 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-27016814

RESUMO

Although the widely used metal oxide nanoparticles (NPs) titanium dioxide NPs (n-TiO2), cerium dioxide NPs (n-CeO2), and zinc oxide NPs (n-ZnO) have been well known for their potential cytotoxicities to environmental organisms, their combined effects have seldom been investigated. In this study, the short-term binary effect of n-CeO2 and n-TiO2 or n-ZnO on a model ammonia oxidizing bacterium, Nitrosomonas europaea were evaluated based on the examinations of cells' physiological, metabolic, and transcriptional responses. The addition of n-TiO2 mitigated the negative effect of more toxic n-CeO2 and the binary toxicity (antagonistic toxicity) of n-TiO2 and n-CeO2 was generally lower than the single NPs induced one. While the n-CeO2/n-ZnO mixture exerted higher cytotoxicity (synergistic cytotoxicity) than that from single NPs. The increased addition of the less toxic n-CeO2 exaggerated the binary toxicity of n-CeO2/n-ZnO mixture although the solubility of n-ZnO was not significantly affected, which excluded the contribution of the dissolved Zn ions to the enhancement of the combined cytotoxicity. The cell membrane disturbances and NP internalizations were detected for all the NP impacted cultures and the electrostatic interactions among the two distinct NPs and the cells were expected to play a key role in mediating their direct contacts and the eventual binary nanotoxicity to the cells.


Assuntos
Cério/toxicidade , Nanopartículas Metálicas/toxicidade , Nitrosomonas europaea/efeitos dos fármacos , Titânio/toxicidade , Óxido de Zinco/toxicidade , Membrana Celular/efeitos dos fármacos , Testes de Sensibilidade Microbiana , Nitrosomonas europaea/metabolismo , Oxirredução , Esgotos/microbiologia
6.
Environ Sci Pollut Res Int ; 23(13): 13023-34, 2016 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-26996914

RESUMO

The short-term combined effects of two most extensively used nanoparticles (NPs) TiO2 NPs (n-TiO2) and ZnO NPs (n-ZnO) versus their individual cytotoxicities on a model ammonia-oxidizing bacterium, Nitrosomonas europaea, were investigated at both physiological and transcriptional levels. n-ZnO exerted more serious impairment effects on cell morphology, cell density, membrane integrity, and ammonia monooxygenase activity than n-TiO2. However, the co-existing n-TiO2 displayed a dose-dependent mitigation effect on n-ZnO cytotoxicity. Consistently, the n-TiO2 and n-ZnO mixture-impacted global transcriptional expression profile, obtained with the whole-genome microarray technique, was more comparable to the n-TiO2-impacted one than that impacted by n-ZnO. The expressions of numerous genes associated with heavy metal scavenging, DNA repair, and oxidative stress response were less up-regulated under the binary impacts of NP mixture than n-ZnO. Moreover, only n-ZnO alone stimulated the up-regulations of heavy metal resistance genes, which further implied the capacity of co-existing n-TiO2 to alleviate n-ZnO cytotoxicity. In addition, the damage of cell membrane structures and the suppression of cell membrane biogenesis-related gene expressions under the influence of either individual NPs or their combinations strongly suggested that the interruption of cell membranes and the associated metabolic activities would probably be one of NPs' critical cytotoxicity mechanisms.


Assuntos
Nanopartículas Metálicas/administração & dosagem , Nitrosomonas europaea/efeitos dos fármacos , Titânio/farmacologia , Transcrição Genética/efeitos dos fármacos , Óxido de Zinco/farmacologia , Nitrosomonas europaea/genética , Oxirredução
7.
Environ Sci Technol ; 49(16): 9460-8, 2015 Aug 18.
Artigo em Inglês | MEDLINE | ID: mdl-26132866

RESUMO

Increasing rare earth element (REE) supplies by recycling and expanded ore processing will result in generation of new wastewaters. In some cases, disposal to a sewage treatment plant may be favored, but plant performance must be maintained. To assess the potential effects of such wastewaters on biological treatment, model nitrifying organisms Nitrosomonas europaea and Nitrobacter winogradskyi were exposed to simulated wastewaters containing varying levels of yttrium or europium (10, 50, and 100 ppm), and the extractant tributyl phosphate (TBP, at 0.1 g/L). Y and Eu additions at 50 and 100 ppm inhibited N. europaea, even when virtually all of the REE was insoluble. Provision of TBP with Eu increased N. europaea inhibition, although TBP alone did not substantially alter activity. For N. winogradskyi cultures, Eu or Y additions at all tested levels induced significant inhibition, and nitrification shut down completely with TBP addition. REE solubility was calculated using the previously developed MSE (Mixed-Solvent Electrolyte) thermodynamic model. The model calculations reveal a strong pH dependence of solubility, typically controlled by the precipitation of REE hydroxides but also likely affected by the formation of unknown phosphate phases, which determined aqueous concentrations experienced by the microorganisms.


Assuntos
Metais Terras Raras/química , Nitrificação , Reciclagem , Águas Residuárias/química , Amônia/química , Concentração de Íons de Hidrogênio , Nitrificação/efeitos dos fármacos , Nitritos/farmacologia , Nitrobacter/efeitos dos fármacos , Nitrosomonas europaea/efeitos dos fármacos , Organofosfatos/farmacologia , Oxirredução/efeitos dos fármacos , Solubilidade , Soluções , Termodinâmica
8.
Environ Toxicol Chem ; 34(10): 2231-5, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26010547

RESUMO

Nitrifying bacteria are highly susceptible to silver nanoparticles (AgNPs). However, the effect of sublethal exposure to AgNPs after their release of nitrogenous compounds of environmental concern (e.g., the greenhouse gas nitrous oxide [N2 O] and the common water pollutant nitrite [NO2 -]) has not been systematically investigated. The present study reports the effect of AgNPs (and potentially released silver ions [Ag(+) ]) on NO2 - and N2 O production by Nitrosomonas europaea, and on the transcription of the associated genes. The release of NO2 - was more negatively affected than the production of N2 O. For example, exposure to AgNPs at 0.075 mg/L temporarily enhanced N2 O production (by 12%) without affecting nitrite release, whereas higher AgNP concentrations (>0.25 mg/L) inhibited NO2 - release (by >12%) but not N2 O production. Transcriptomic analyses corroborated these trends; AgNPs at 0.075 mg/L increased the expression of the nitric oxide reductase gene (norQ) associated with N2 O production (by 5.3-fold to 12.8-fold), whereas both 0.075 mg/L of Ag(+) and 0.75 mg/L of AgNPs down-regulated the ammonia monooxygenase gene (amoA2; by 0.08-fold to 0.15-fold and 0.32-fold to 0.64-fold, respectively), the nitrite reductase gene (nirK; by 0.01-fold to 0.02-fold and 0.22-fold to 0.44-fold, respectively), and norQ (by 0.11-fold to 0.15-fold and 0.32-fold to 0.57-fold, respectively). These results suggest that AgNP release to sewage treatment plants and land application of AgNP-containing biosolids should be minimized because of their potential temporary stimulation of N2 O release and interference with nitrification. Environ Toxicol Chem 2015;34:2231-2235. © 2015 SETAC.


Assuntos
Nanopartículas Metálicas/química , Nitrosomonas europaea/metabolismo , Óxido Nitroso/metabolismo , Prata/química , Cromatografia Gasosa , Nanopartículas Metálicas/toxicidade , Nitrificação/efeitos dos fármacos , Nitritos/análise , Nitritos/metabolismo , Nitrosomonas europaea/efeitos dos fármacos , Nitrosomonas europaea/enzimologia , Óxido Nitroso/análise , Oxirredutases/genética , Oxirredutases/metabolismo , Transcrição Genética
9.
Chemosphere ; 128: 207-15, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25710320

RESUMO

Nanosized TiO2 (n-TiO2), CeO2 (n-CeO2), and ZnO (n-ZnO) and bulk ZnO were chosen for a 4-h exposure study on a model ammonia oxidizing bacterium, Nitrosomonas europaea. n-ZnO displayed the most serious cytotoxicity while n-TiO2 was the least toxic one. The change of cell morphologies, the retardance of specific oxygen uptake rates and ammonia oxidation rates, and the depression of amoA gene expressions under NP stresses were generally observed when the cell densities and membrane integrities were not significantly impaired yet. The TEM imaging and the synchrotron X-ray fluorescence microscopy of the NPs impacted cells revealed the increase of the corresponding intracellular Ti, Ce or Zn contents and suggested the intracellular NP accumulation. The elevation of intracellular S contents accompanied with higher K contents implied the possible activation of thiol-containing glutathione and thioredoxin production for NP stress alleviation. The NP cytotoxicity was not always a function of NP concentration. The 200 mg L(-1) n-TiO2 or n-CeO2 impacted cells displayed the similar ammonia oxidation activities but higher amoA gene expression levels than the 20 mg L(-1) NPs impacted ones. Such phenomenon further indicated the possible establishment of an anti-toxicity mechanism in N. europaea at the genetic level to redeem the weakened AMO activities along with the NP aggregation effects.


Assuntos
Cério/toxicidade , Regulação da Expressão Gênica/efeitos dos fármacos , Nanopartículas/toxicidade , Nitrosomonas europaea/efeitos dos fármacos , Titânio/toxicidade , Óxido de Zinco/toxicidade , Amônia/metabolismo , Glutationa/metabolismo , Microscopia Eletrônica de Transmissão , Microscopia de Fluorescência , Nanopartículas/ultraestrutura , Nitrosomonas europaea/metabolismo , Oxirredução/efeitos dos fármacos , Oxigênio/metabolismo , Síncrotrons , Tiorredoxinas/metabolismo
10.
Environ Toxicol Chem ; 34(4): 887-97, 2015 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-25556815

RESUMO

Proper characterization of nanoparticle (NP) interactions with environmentally relevant bacteria under representative conditions is necessary to enable their sustainable manufacture, use, and disposal. Previous nanotoxicology research based on planktonic growth has not adequately explored biofilms, which serve as the predominant mode of bacterial growth in natural and engineered environments. Copper nanoparticle (Cu-NP) impacts on biofilms were compared with respective planktonic cultures of the ammonium-oxidizing Nitrosomonas europaea, nitrogen-fixing Azotobacter vinelandii, and denitrifying Paracoccus denitrificans using a suite of independent toxicity diagnostics. Median inhibitory concentration (IC50) values derived from adenosine triphosphate (ATP) for Cu-NPs were lower in N. europaea biofilms (19.6 ± 15.3 mg/L) than in planktonic cells (49.0 ± 8.0 mg/L). However, in absorbance-based growth assays, compared with unexposed controls, N. europaea growth rates in biofilms were twice as resilient to inhibition than those in planktonic cultures. Similarly, relative to unexposed controls, growth rates and yields of P. denitrificans in biofilms exposed to Cu-NPs were 40-fold to 50-fold less inhibited than those in planktonic cells. Physiological evaluation of ammonium oxidation and nitrate reduction suggested that biofilms were also less inhibited by Cu-NPs than planktonic cells. Furthermore, functional gene expression for ammonium oxidation (amoA) and nitrite reduction (nirK) showed lower inhibition by NPs in biofilms relative to planktonic-grown cells. These results suggest that biofilms mitigate NP impacts, and that nitrogen-cycling bacteria in wastewater, wetlands, and soils might be more resilient to NPs than planktonic-based assessments suggest.


Assuntos
Bactérias/efeitos dos fármacos , Bactérias/crescimento & desenvolvimento , Biofilmes/crescimento & desenvolvimento , Cobre/toxicidade , Poluentes Ambientais/toxicidade , Nanopartículas Metálicas/toxicidade , Fixação de Nitrogênio , Plâncton/microbiologia , Compostos de Amônio/metabolismo , Azotobacter vinelandii/efeitos dos fármacos , Azotobacter vinelandii/crescimento & desenvolvimento , Regulação Bacteriana da Expressão Gênica/efeitos dos fármacos , Nitratos/metabolismo , Nitrosomonas europaea/efeitos dos fármacos , Nitrosomonas europaea/crescimento & desenvolvimento , Oxirredução , Paracoccus denitrificans/efeitos dos fármacos , Paracoccus denitrificans/crescimento & desenvolvimento
11.
Environ Sci Technol ; 47(24): 14403-10, 2013 Dec 17.
Artigo em Inglês | MEDLINE | ID: mdl-24219026

RESUMO

Bovine serum albumin (BSA), a model protein, reduced the toxicity of 20 nm citrate silver nanoparticles (AgNP) toward Nitrosomonas europaea, a model ammonia oxidizing bacteria, through a dual-mode protection mechanism. BSA reduced AgNP toxicity by chelating the silver ions (Ag(+)) released from the AgNPs. BSA further reduced AgNP toxicity by binding to the AgNP surface thus preventing NH3-dependent dissolution from occurring. Due to BSA's affinity toward Ag(+) chemisorbed on the AgNP surface, increased concentrations of BSA lead to increased AgNP dissolution rates. This, however, did not increase AgNP toxicity as the dissolved Ag(+) were adsorbed onto the BSA molecules. Alginate, a model extracellular polysaccharide (EPS), lacks strong Ag(+) ligands and was unable to protect N. europaea from Ag(+) toxicity. However, at high concentrations, alginate reduced AgNP toxicity by binding to the AgNP surface and reducing AgNP dissolution rates. Unlike BSA, alginate only weakly interacted with the AgNP surface and was unable to completely prevent NH3-dependent AgNP dissolution from occurring. Based on these results, AgNP toxicity in high protein environments (e.g., wastewater) is expected to be muted while the EPS layers of wastewater biofilms may provide additional protection from AgNPs, but not from Ag(+) that have already been released.


Assuntos
Alginatos/química , Nanopartículas Metálicas/toxicidade , Nitrosomonas europaea/efeitos dos fármacos , Soroalbumina Bovina/química , Prata/toxicidade , Testes de Toxicidade , Animais , Bovinos , Ácido Glucurônico/química , Ácidos Hexurônicos/química , Nanopartículas Metálicas/química , Nitrificação/efeitos dos fármacos , Prata/química , Solubilidade , Espectrofotometria Ultravioleta
12.
Chemosphere ; 93(10): 2493-8, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-24120011

RESUMO

Nitrosomonas europaea, a model ammonia oxidizing bacterium, was sensitive to both ionic silver (Ag(+)) and 20 nm citrate capped silver nanoparticles (AgNPs). AgNP toxicity has been previously shown to be primarily due to the dissolution of Ag(+). The rate of AgNP dissolution dramatically increased in test medium containing ammonium sulfate ((NH4)2SO4) and HEPES buffer compared to test medium containing either deionized water or HEPES buffer alone. The AgNP dissolution rates accelerated with increases in ammonia (NH3) concentrations either through increases in pH or through higher (NH4)2SO4 concentrations. Ammonia likely participated in the oxidation of the AgNP to form [Formula: see text] in solution leading to the observed increase in AgNP dissolution rates. AgNP toxicity was enhanced as NH3 concentrations increased. However, Ag(+) toxicity was constant at all NH3 concentrations tested. Therefore, it can be concluded that the increased AgNP toxicity was due to increased Ag(+) release and not due to a synergistic effect between NH3 and Ag(+). The results of this study may provide insights in the fate and toxicity of AgNPs in high NH3 environments including wastewater treatment plants, eutrophic waterways and alkaline environments.


Assuntos
Amônia/química , Nanopartículas Metálicas/toxicidade , Nitrosomonas europaea/efeitos dos fármacos , Prata/toxicidade , Poluentes Químicos da Água/toxicidade , Nanopartículas Metálicas/química , Nitrosomonas europaea/fisiologia , Prata/química , Poluentes Químicos da Água/química
13.
Water Res ; 47(13): 4692-700, 2013 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-23770483

RESUMO

Ammonia oxidation by Nitrosomonas europaea, an ammonia oxidizing bacterium prevalent in wastewater treatment, is inhibited in the presence of phenol, due to interaction of the phenol with the ammonia monooxygenase enzyme. Suspended cells of N. europaea were cultured in batch reactors and continuous flow reactors at dilution rates of 0.01-0.2 d(-1). The rate of ammonia oxidation in the continuous cultures correlated to the dilution rate in the reactor. The batch and continuous cultures were exposed to 20 µM phenol and ammonia oxidation activity was measured by specific oxygen uptake rates (SOURs). Inhibition of NH3 oxidation by 20 µM phenol ranged from a 77% reduction of SOUR observed with suspended cells harvested during exponential growth, to 26% in biofilms. The extent of inhibition was correlated with ammonia oxidation rates in both suspended and biofilm cells, with greater percent inhibition observed with higher initial rates of NH3 oxidation. In biofilm grown cells, an increase in activity and phenol inhibition were both observed upon dispersing the biofilm cells into fresh, liquid medium. Under higher oxygen tension, an increase in the NO2(-) production of the biofilms was observed and biofilms were more susceptible to phenol inhibition. Dissolved oxygen microsensor measurements showed oxygen limited conditions existed in the biofilms. The ammonia oxidation rate was much lower in biofilms, which were less inhibited during phenol exposure. The results clearly indicate in both suspended and attached cells of N. europaea that a higher extent of phenol inhibition is positively correlated with a higher rate of NH3 oxidation (enzyme turnover).


Assuntos
Amônia/metabolismo , Técnicas de Cultura Celular por Lotes/métodos , Biofilmes/crescimento & desenvolvimento , Nitrosomonas europaea/efeitos dos fármacos , Nitrosomonas europaea/metabolismo , Fenol/farmacologia , Biofilmes/efeitos dos fármacos , Reatores Biológicos/microbiologia , Nitritos/metabolismo , Nitrosomonas europaea/fisiologia , Oxirredução/efeitos dos fármacos , Oxigênio/metabolismo
14.
Water Res ; 47(13): 4701-9, 2013 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-23770484

RESUMO

Chloramine is widely used in United States drinking water systems as a secondary disinfectant, which may promote the growth of nitrifying bacteria because ammonia is present. At the onset of nitrification, both nitrifying bacteria and their products exert a monochloramine demand, decreasing the residual disinfectant concentration in water distribution systems. This work investigated another potentially significant mechanism for residual disinfectant loss: monochloramine cometabolism by ammonia-oxidizing bacteria (AOB). Monochloramine cometabolism was studied with the pure culture AOB Nitrosomonas europaea (ATCC 19718) in batch kinetic experiments under drinking water conditions. Three batch reactors were used in each experiment: a positive control to estimate the ammonia kinetic parameters, a negative control to account for abiotic reactions, and a cometabolism reactor to estimate the cometabolism kinetic constants. Kinetic parameters were estimated in AQUASIM with a simultaneous fit to all experimental data. The cometabolism reactors showed a more rapid monochloramine decay than in the negative controls, demonstrating that cometabolism occurs. Cometabolism kinetics were best described by a pseudo first order model with a reductant term to account for ammonia availability. Monochloramine cometabolism kinetics were similar to those of ammonia metabolism, and monochloramine cometabolism was a significant loss mechanism (30-60% of the observed monochloramine decay). These results suggest that monochloramine cometabolism should occur in practice and may be a significant contribution to monochloramine decay during nitrification episodes in drinking water distribution systems.


Assuntos
Cloraminas/metabolismo , Água Potável/microbiologia , Nitrosomonas europaea/metabolismo , Amônia/metabolismo , Cloreto de Amônio/farmacologia , Técnicas de Cultura Celular por Lotes , Biodegradação Ambiental/efeitos dos fármacos , Biomassa , Simulação por Computador , Cinética , Modelos Biológicos , Nitrosomonas europaea/efeitos dos fármacos
15.
Environ Toxicol Chem ; 32(7): 1488-94, 2013 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-23554086

RESUMO

The widespread use of silver nanoparticles (AgNPs) raises the potential for environmental releases that could impact microbial ecosystem services. In the present study, the authors address how the AgNPs and Ag(+) that they release may impact nitrogen-cycling bacteria. The authors studied the cellular and transcriptional response of the denitrifier Pseudomonas stutzeri, the nitrogen fixer Azotobacter vinelandii, and the nitrifier Nitrosomonas europaea exposed to 35 nm (carbon-coated) AgNPs or to Ag(+) (added as AgNO3 ). Based on minimum inhibitory concentrations (MICs), Ag(+) was 20 times to 48 times more toxic to the tested strains than AgNPs (including Ag(+) released during exposure). Exposure to sublethal concentrations of AgNPs or Ag(+) (representing 10% of the respective MIC for AgNO3 ) resulted in no significant effect on the expression of the denitrifying genes narG, napB, nirH, and norB in P. stutzeri or the nitrogen-fixing genes nifD, nifH, vnfD, and anfD in A. vinelandii, whereas nitrifying genes (amoA1 and amoC2) in N. europaea were upregulated (2.1- to 3.3-fold). This stimulatory effect disappeared at higher silver concentrations (60% of the Ag(+) MIC), and toxicity was exerted at concentrations higher than 60% of the Ag(+) MIC. The MIC for N. europaea was 8 times to 24 times lower than for the other strains, indicating higher susceptibility to AgNPs. This was corroborated by the lower half-lethal concentration for N. europaea (87 µg/L) compared with P. stutzeri (124 µg/L) and A. vinelandii (>250 µg/L) when cells were exposed with Ag(+) for 24 h in 1 mM bicarbonate buffer. This suggests that ammonia oxidation would be the most vulnerable nitrogen-cycling process in wastewater treatment plants receiving AgNPs and in agricultural soils amended with biosolids that concentrate them.


Assuntos
Nanopartículas Metálicas/toxicidade , Ciclo do Nitrogênio/efeitos dos fármacos , Pseudomonas stutzeri/efeitos dos fármacos , Prata/toxicidade , Transcrição Genética/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Desnitrificação , Genes Bacterianos , Nitrogênio/análise , Nitrogênio/metabolismo , Nitrosomonas europaea/efeitos dos fármacos , Pseudomonas stutzeri/genética , Pseudomonas stutzeri/metabolismo , Microbiologia da Água
16.
Mar Pollut Bull ; 68(1-2): 64-70, 2013 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-23385120

RESUMO

The toxicity of the water associated fraction (WAF) of Alaska North Slope Crude oil (ANSC), Corexit 9500A and the dispersant enhanced WAF (DEWAF) of ANSC:Corexit 9500A mixtures were examined on the model ammonia oxidizing bacterium, Nitrosomonas europaea. Corexit 9500A was not toxic at environmentally relevant concentrations. Corexit 9500A greatly increased the toxicity of ANSC by increasing the chemical oxygen demand (COD) of the DEWAF. However, a majority of the DEWAF compounds were not toxic to N. europaea. Weathered WAF and DEWAF were not toxic to N. europaea even though their COD did not change compared to non-weathered controls, suggesting that toxicity was due to a small volatile fraction of the ANSC. The over-expression of the NE1545 gene, a marker for aromatic hydrocarbon exposure, in N. europaea cells exposed to WAF and DEWAF suggests that aromatic hydrocarbons are bioavailable to the cells and may play a role in the observed toxicity.


Assuntos
Lipídeos/toxicidade , Nitrosomonas europaea/efeitos dos fármacos , Petróleo/toxicidade , Tensoativos/toxicidade , Poluentes Químicos da Água/toxicidade , Alaska , Amônia/análise , Amônia/metabolismo , Nitrosomonas europaea/fisiologia , Poluentes Químicos da Água/análise , Tempo (Meteorologia)
17.
Chemosphere ; 90(4): 1404-11, 2013 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-22985593

RESUMO

In this study, Nitrosomonas europaea ATCC 19718 was exposed to silver nanoparticles (AgNPs) of different particle size (7±3 and 40±14nm) and different coatings (polyvinyl alcohol and adenosine triphosphate disodium). For all different AgNPs used in the study, large aggregates were gradually formed after addition of AgNPs into the media containing N. europaea. The scanning electron microscopy and energy dispersive X-ray spectroscopy of the microstructures suggested that bacterial cells and electrolytes had significant effects on AgNP aggregation. Size- and coating-dependent inhibition of ammonia oxidation by AgNPs was observed, and our analysis suggested that the inhibition was not only due to the released dissolved silver, but also the dispersity of AgNPs in the culture media. Electron microscopy images showed AgNPs could cause the damage of cell wall of N. europaea and make the nucleoids disintegrated and condensed next to cell membrane. Surface-enhanced Raman scattering signals also implied the damage of cell membrane caused by AgNPs. Further protein expression analysis revealed that AgNPs would inhibit important protein functions, including biosynthesis, gene expression, energy production and nitrification to further cause toxicity to N. europaea. Our findings explain the susceptibility of N. europaea to inhibition by AgNPs and the possible interaction between each other. Future research is needed to characterize these effects in more complex cultures and media such as activated sludge and wastewater.


Assuntos
Substâncias Perigosas/toxicidade , Nanopartículas Metálicas/toxicidade , Nitrosomonas europaea/efeitos dos fármacos , Prata/toxicidade , Nanopartículas Metálicas/química , Nanopartículas Metálicas/ultraestrutura , Microscopia Eletrônica de Varredura , Nitrificação , Nitrosomonas europaea/fisiologia , Prata/química , Análise Espectral Raman
18.
Environ Sci Technol ; 46(10): 5387-95, 2012 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-22533675

RESUMO

Silver nanoparticles (AgNPs) are increasingly used as bacteriostatic agents to prevent microbial growth. AgNPs are manufactured with a variety of coatings, and their potential impacts on wastewater treatment in general are poorly understood. In the present study, Nitrosomonas europaea, a model ammonia oxidizing bacterium, was exposed to AgNPs with citrate, gum arabic (GA), and polyvinylpyrrolidone (PVP). GA and citrate AgNPs inhibited nitrification most strongly (67.9 ± 3.6% and 91.4 ± 0.2%, respectively at 2 ppm). Our data indicate that Ag(+) dissolution and colloid stability of AgNPs were the main factors in AgNP toxicity. In general, low amounts of dissolved Ag initially caused a post-transcriptional interruption of membrane-bound nitrifying enzyme function, reducing nitrification by 10% or more. A further increase in dissolved Ag resulted in heavy metal stress response (e.g., merA up-regulation) and ultimately led to membrane disruption. The highest effect on membrane disruption was observed for citrate AgNPs (64 ± 11% membranes compromised at 2 ppm), which had high colloidal stability. This study demonstrates that coating plays a very important role in determining Ag dissolution and ultimately toxicity to nitrifiers. More research is needed to characterize these parameters in complex growth media such as wastewater.


Assuntos
Ácido Cítrico/química , Goma Arábica/química , Nanopartículas Metálicas/química , Nitrificação/efeitos dos fármacos , Nitrosomonas europaea/efeitos dos fármacos , Povidona/química , Prata/farmacologia , Membrana Celular/efeitos dos fármacos , Membrana Celular/ultraestrutura , Cisteína/farmacologia , Regulação Bacteriana da Expressão Gênica/efeitos dos fármacos , Inativação Gênica/efeitos dos fármacos , Genes Bacterianos/genética , Nanopartículas Metálicas/ultraestrutura , Viabilidade Microbiana/efeitos dos fármacos , Nitritos/análise , Nitrosomonas europaea/citologia , Nitrosomonas europaea/genética , Nitrosomonas europaea/ultraestrutura , RNA Ribossômico 16S/genética , Solubilidade/efeitos dos fármacos
19.
Chemosphere ; 82(4): 565-72, 2011 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-20980043

RESUMO

Pharmaceutically active compounds (PhACs) are commonly found in wastewater influent. However, little research has focused on determining their impact on fundamental processes in wastewater treatment such as nitrogen removal. In this study, focus was placed on 4 commonly occurring PhACs (ketoprofen, naproxen, carbamazepine and gemfibrozil). Their effect was ascertained in the ammonia oxidizing bacterium (AOB), Nitrosomonas europaea in terms of membrane integrity and nitrite production. These PhACs were shown to inhibit nitrite production at concentrations of 1 and 10 µM while no effect was observed at 0.1 µM. The maximum observed nitrification inhibition was 25%, 29%, 22% and 26% for ketoprofen, naproxen, carbamazepine and gemfibrozil, respectively. A decrease in the live/dead ratio ranging from 10% to 16% suggests that these PhACs affect membrane integrity in N.europaea. The difference in nitrite production between PhACs treated cells and non PhAC treated controls was still significant following washing suggesting that inhibition is irreversible. Finally, nitrite production when adjusted to the live fraction of cells was also found to decrease suggesting that PhACs inhibited the activity of surviving cells. These results suggest that the presence of PhACs may affect AOB activity and may impact nitrogen removal, a key function in wastewater treatment. Follow up studies with additional AOB and in mixed culture are needed to further confirm these results.


Assuntos
Amônia/metabolismo , Nitrosomonas europaea/efeitos dos fármacos , Preparações Farmacêuticas , Poluentes Químicos da Água/toxicidade , Nitrificação , Nitrogênio/metabolismo , Nitrosomonas europaea/metabolismo , Eliminação de Resíduos Líquidos
20.
Chemosphere ; 82(4): 514-20, 2011 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-21106218

RESUMO

Nitrosomonas europaea, a model ammonia oxidizing bacterium, was exposed to a wide variety of aromatic hydrocarbons in 3 h batch assays. The expression of NE1545, a phenol sentinel gene involved in fatty acid metabolism, was monitored via quantitative real-time polymerase chain reaction (qRT-PCR) and a Coulter Counter technique was used to monitor changes in cell volume. Decreases in cell volume and NE1545 gene expression correlated strongly with exposure to aromatic hydrocarbons that possessed a single polar group substitution (e.g. phenol and aniline). Aromatic hydrocarbons that contain no polar group substitutions (e.g. toluene) or multiple polar group substitutions (e.g. p-hydroquinone) caused negligible changes in NE1545 expression and cell volume. The oxidation of aromatic hydrocarbons by N. europaea from configurations without a single polar group to one with two polar groups (e.g. p-cresol oxidized to 4-hydroxybenzyl alcohol) and from configurations with no polar groups to one with a single polar group (e.g. ethylbenzene oxidized to 4-ethylphenol) greatly influenced NE1545 gene expression and observed changes in cell volume. Nitrification inhibition in N. europaea by the aromatic hydrocarbons was found to be completely reversible; however, the decreases in cell volume were not reversible suggesting a physical change in cell membrane composition. Ammonia monooxygenase blocking studies showed that the chemical exposure that was responsible for the cell volume decrease and up-regulation in gene expression and not the observed inhibition. N. europaea is the first bacterium shown to experience significant changes in cell volume when exposed to µM concentrations of aromatic hydrocarbons, three orders of magnitude lower than previous studies with other bacteria.


Assuntos
Expressão Gênica/efeitos dos fármacos , Hidrocarbonetos Aromáticos/toxicidade , Nitrosomonas europaea/genética , Poluentes Químicos da Água/toxicidade , Genes Bacterianos , Hidrocarbonetos Aromáticos/metabolismo , Nitrosomonas europaea/efeitos dos fármacos , Nitrosomonas europaea/metabolismo , Oxirredução , Poluentes Químicos da Água/metabolismo
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