Selection and identification of bacterial strains with methyl-tert-butyl ether, ethyl-tert-butyl ether, and tert-amyl methyl ether degrading capacities

Nine bacterial strains isolated from two hydrocarbon-contaminated soils were selected because of their capacity for growth in culture media amended with 200 mg/L of one of the following gasoline oxygenates: Methyl-tert-butyl ether (MTBE), ethyl-tert-butyl ether (ETBE), and tert-amyl methyl ether (TAME). These strains were identified by amplification of their 16S rRNA gene, using fDl and rD1 primers, and were tested for their capacity to grow and biotransform these oxygenates in both mineral and cometabolic media. The isolates were classified as Bacillus simplex, Bacillus drentensis, Arthrobacter sp., Acinetobacter calcoaceticus, Acinetobacter sp., Gordonia amicalis (two strains), Nocardioides sp., and Rhodococcus ruber. Arthrobacter sp. (strain MG) and A. calcoaceticus (strain M10) consumed 100 (cometabolic medium) and 82 mg/L (mineral medium) of oxygenate TAME in 21 d, respectively, under aerobic conditions. Rhodococcus ruber (strain E10) was observed to use MTBE and ETBE as the sole carbon and energy source, whereas G. amicalis (strain T3) used TAME as the sole carbon and energy source for growth. All the bacterial strains transformed oxygenates better in the presence of an alternative carbon source (ethanol) with the exception of A. calcoaceticus (strain M10). The capacity of the selected strains to remove MTBE, ETBE, and TAME looks promising for application in bioremediation technologies.     

Ecofriendly degradation, decolorization and detoxification of textile effluent by a developed bacterial consortium

Present study illustrates the effectual decolorization and degradation of the textile effluent using a developed bacterial consortium SDS, consisted of bacterial species Providencia sp. SDS and Pseudomonas aeuroginosa strain BCH, originally isolated from dye contaminated soil. The intensive metabolic activity of the consortium SDS led to complete decolorization of textile effluent within 20 h at pH 7 and temperature 30 °C. Significant induction in the activities of veratryl alcohol oxidase, laccase, azoreductase and DCIP reductase were observed during decolorization, which indicates their involvement in decolorization and degradation process. The decolorization and biodegradation was monitored using UV-vis spectroscopy, IR spectroscopy, HPLC and HPTLC analysis. Toxicological analysis of effluent before and after treatment was performed using classical Allium cepa test. Investigations of various toxicological parameters viz, oxidative stress response, cytotoxicity, genotoxicity and phytotoxicity, collectively concludes that, the toxicity of effluent reduces significantly after treatment with consortium SDS.     

Aerobic and anaerobic biodegradation of nitrilotriacetate in subsurface soils

Studies were conducted to characterize mineralization of nitrilotriacetate (NTA) in subsurface soils under aerobic and anaerobic conditions. Chemical (redox indicator, resazurin) and biological (dentrification) markers were used as indicators of anaerobic conditions in the test system. The indigenous microflora in subsurface soils previously exposed to septage containing NTA were able to rapidly mineralize NTA under aerobic and anaerobic conditions. The half-lives (t1/2) of mineralization for NTA in aerobic soils ranged from 87 to 160 hr. Biodegradation of NTA under anaerobic conditions where NO3- indicates that a mechanism exists for the anaerobic biodegradation of this substrate. NTA biodegradation can occur readily in the absence of molecular oxygen and the NTA-monooxygenase which are required for the aerobic mineralization of this substrate. These results provide the first evidence that the indigenous microflora in subsurface soils of septic tank tile fields can rapidly degrade NTA under anaerobic conditions.     

Aerobic fitness and the physiological stress response: a critical evaluation

Aerobically fit persons need less sympathetic activation to perform the same absolute workload than less fit persons. This led to the idea that aerobic fitness might reduce the physiological activation during psychological stress as well. Several experiments showed inconsistent results with regard to this supposed effect of fitness. The comparability of the results is hampered by the differences in operationalization of aerobic fitness and by the confusion of the terms aerobic fitness, training and habitual physical exercise. The expectancy of an effect of fitness on the physiological stress response is based on the assumption that this response resembles the response to exercise. The tenability of this assumption was examined for cardiac, vascular and hormonal responses respectively. It was concluded that the two types of responses only superficially have similarity. So a simple analogy between the stress and the exercise response does not allow a reliable prediction concerning the effect of fitness on the stress response. There are however other reasons to expect an effect. Especially the effect of fitness on adrenoceptor sensitivity suggests that the most important effect of fitness might be found in the vascular part of the stress response. It is argued that the measurement of complete response patterns, instead of isolated parameters, is a prerequisite for progress in this field. Future studies should address the question what the relative contribution of psychological and physiological factors is to the effect of fitness on the physiological stress response.     

Aerobic biodegradation of aliphatic polyethoxylates: an 1H-nuclear magnetic resonance spectroscopy investigation

Aerobic biodegradation tests of three blends representative of the most commonly marketed aliphatic alcohol polyethoxylates (AE) and a commercial polyethylene glycols (PEG) mixture were run under standard test conditions (Organization for Economic Cooperation and Development, Paris, France [OECD] 301 E protocol). The test liquors were investigated using a 400-MHz proton-nuclear magnetic resonance (1H-NMR) spectrometer in order to elucidate the biodegradation mechanism. Diagnostic signals for both linear and branched AE homologs were identified by bidimensional homocorrelated spectroscopy (COSY) and by double quantum filter correlated spectroscopy (DQFCOSY). The 1H-NMR allowed individually monitoring the fate of the alkyl and polyethoxyl fragments of the parent compounds and distinguishing between oxidative and nonoxidative polyethoxyl depolymerization, which could not be performed by other reported techniques such as high-peformance liquid chromatography (HPLC) or mass spectrometry (MS) or FAB spectroscopy. The AE biodegradation time profiles showed that under the test conditions, both alkyl and polyethoxyl chains of the linear and oxo-AE were biodegraded quite readily. The removal of the multibranched AE was slower when compared to that of linear and oxo-AE, while PEG exhibited a time profile characterized by a biodegradation rate significantly slower than that of PEG released by the microbial attack of linear and oxo-AE. In the case of linear AE, the alkyl chain was biodegraded much faster than the polyethoxyl chain, while in the case of oxo- and multibranched AE, both the alkyl and the polyethoxyl chains were biodegraded at similar rates.     

Aerobic degradation and photolysis of tylosin in water and soil

Veterinary antibiotics enter the environment through the application of organic fertilizers to cropland. In this study, the aerobic degradation of tylosin, a widely used antibiotic in the production of livestock and poultry, was conducted in water and in soil in an effort to further investigate its environmental fate. Tylosin is a macrolide antibiotic, which consists of four factors (A, B, C, D). Water and soil were sampled at selected times and analyzed for tylosin and its degradation products by high-performance liquid chromatography (HPLC), with product identification confirmed by HPLC-mass spectrometry. Tylosin A is degraded with a half-life of 200 d in the light in water, and the total loss of tylosin A in the dark is 6% of the initial spiked amount during the experimental period. Tylosin C and D are relatively stable except in ultrapure water in the light. Slight increases of tylosin B after two months and formation of two photoreaction isomers of tylosin A were observed under exposure to light. However, tylosin probably would degrade faster if the experimental containers did not prevent ultraviolet transmission. In soil, tylosin A has a dissipation half-life of 7 d, and tylosin D is slightly more stable, with a dissipation half-life of 8 d in unsterilized and sterilized soil. Sorption and abiotic degradation are the major factors influencing the loss of tylosin in the environment, and no biotic degradation was observed at the test concentration either in pond water or in an agronomic soil, as determined by comparing dissipation profiles in sterilized and unsterilized conditions.     

AGRICOH: a consortium of agricultural cohorts

AGRICOH is a recently formed consortium of agricultural cohort studies involving 22 cohorts from nine countries in five continents: South Africa (1), Canada (3), Costa Rica (2), USA (6), Republic of Korea (1), New Zealand (2), Denmark (1), France (3) and Norway (3). The aim of AGRICOH, initiated by the US National Cancer Institute (NCI) and coordinated by the International Agency for Research on Cancer (IARC), is to promote and sustain collaboration and pooling of data to investigate the association between a wide range of agricultural exposures and a wide range of health outcomes, with a particular focus on associations that cannot easily be addressed in individual studies because of rare exposures (e.g., use of infrequently applied chemicals) or relatively rare outcomes (e.g., certain types of cancer, neurologic and auto-immune diseases). To facilitate future projects the need for data harmonization of selected variables is required and is underway. Altogether, AGRICOH provides excellent opportunities for studying cancer, respiratory, neurologic, and auto-immune diseases as well as reproductive and allergic disorders, injuries and overall mortality in association with a wide array of exposures, prominent among these the application of pesticides.     

Legionnaires' disease: evaluation of a quantitative microbial risk assessment model

Background: The quantities of Legionella vary considerably from natural waters to water in contaminated domestic hot water supplies, whirlpool spas and cooling towers, with the risk for LD rising as the Legionella counts grow. We currently report the results from our Quantitative Microbial Risk Assessment (QMRA) model evaluation. We developed the LD QMRA model to better understand Legionella exposure risks.     

Aerobic residential onsite sewage systems: an evaluation of treated-effluent quality

This retrospective cohort study used existing data to evaluate the quality of effluent from three of the most common types of onsite residential aerobic treatment sewage systems (Multi-Flo, Norweco, and Whitewater) installed in Kitsap County, Washington. Five-day biochemical oxygen demand (BOD5), total suspended solids (TSS), and fecal-coliform-bacteria parameters were used to determine performance. Although most (77 percent) of the systems were less than one year old at the time of sampling, over a third failed to meet NSF certification standards for BOD5 and TSS in effluent (< 30 milligrams per liter [mg/L]). Over two-thirds of systems failed to meet Washington State Board of Health Treatment Standard 2 criteria for BOD5 and TSS (< 10 mg/L). Furthermore, an average of 59 percent of the systems failed to meet state standards for fecal coliform (< 800 fecal coliform bacteria per 100 milliliters).     

Aerobic degradation of tylosin in cattle,chicken, and swine excreta

Tylosin, a fermentation-derived macrolide antibiotic, was tested to determine its aerobic degradation rate in cattle, chicken, and swine excreta. For chicken, excreta from a hen administered 14C-tylosin as part of a metabolism study were used. For cattle and swine, 14C-tylosin was added to control excreta. The formation of 14C volatile breakdown products and 14CO2 was not observed throughout the study. Material balance for the carbon-14 label ranged between 94% and 104%. Initial, day-0, concentrations of tylosin-A averaged 119.52+/-4.39, 35.01+/-1.34, and 62.82+/-2.11 microg/g (dry weight basis) for cattle, chicken, and swine excreta samples, respectively. After 30 days, samples averaged 4.16+/-0.69 and 4.11+/-0.69 microg/g tylosin-A in cattle and swine excreta, respectively. No residues of tylosin-A or its factors were apparent in the chicken excreta samples after 30 days of incubation. In each case, tylosin declined to less than 6.5% of the initial level after 30 days. Calculated first-order half-lives under the test conditions were 6.2 days, <7.6 days, and 7.6 days for cattle, chicken, and swine excreta, respectively. The results indicate that tylosin residues degrade rapidly in animal excreta. Therefore, tylosin residues should not persist in the environment.     

Wavelet-based compression of medical images: filter-bank selection and evaluation

Wavelet-based image coding algorithms (lossy and lossless) use a fixed perfect reconstruction filter-bank built into the algorithm for coding and decoding of images. However, no systematic study has been performed to evaluate the coding performance of wavelet filters on medical images. We evaluated the best types of filters suitable for medical images in providing low bit rate and low computational complexity. In this study a variety of wavelet filters are used to compress and decompress computed tomography (CT) brain and abdomen images. We applied two-dimensional wavelet decomposition, quantization and reconstruction using several families of filter banks to a set of CT images. Discreet Wavelet Transform (DWT), which provides efficient framework of multi-resolution frequency was used. Compression was accomplished by applying threshold values to the wavelet coefficients. The statistical indices such as mean square error (MSE), maximum absolute error (MAE) and peak signal-to-noise ratio (PSNR) were used to quantify the effect of wavelet compression of selected images. The code was written using the wavelet and image processing toolbox of the MATLAB (version 6.1). This results show that no specific wavelet filter performs uniformly better than others except for the case of Daubechies and bi-orthogonal filters which are the best among all. MAE values achieved by these filters were 5 x 10(-14) to 12 x 10(-14) for both CT brain and abdomen images at different decomposition levels. This indicated that using these filters a very small error (approximately 7 x 10(-14)) can be achieved between original and the filtered image. The PSNR values obtained were higher for the brain than the abdomen images. For both the lossy and lossless compression, the 'most appropriate' wavelet filter should be chosen adaptively depending on the statistical properties of the image being coded to achieve higher compression ratio.     

Effect of ethanol and methyl-tert-butyl ether on monoaromatic hydrocarbon biodegradation: response variability for different aquifer materials under various electron-accepting conditions

Aquifer microcosms were used to determine how ethanol and methyl-tert-butyl ether (MtBE) affect monoaromatic hydrocarbon degradation under different electron-accepting conditions commonly found in contaminated sites experiencing natural attenuation. Response variability was investigated by using aquifer material from four sites with different exposure history. The lag phase prior to benzene, toluene, ethylbenzene, and xylenes (BTEX) and ethanol degradation was typically shorter in microcosms with previously contaminated aquifer material, although previous exposure did not always result in high degradation activity. Toluene was degraded in all aquifer materials and generally under a broader range of electron-accepting conditions compared to benzene, which was degraded only under aerobic conditions. The MtBE was not degraded within 100 d under any condition, and it did not affect BTEX or ethanol degradation patterns. Ethanol was often degraded before BTEX compounds and had a variable effect on BTEX degradation as a function of electron-accepting conditions and aquifer material source. An occasional enhancement of toluene degradation by ethanol occurred in denitrifying microcosms with unlimited nitrate; this may be attributable to the fortuitous growth of toluene-degrading bacteria during ethanol degradation. Nevertheless, experiments with flow-through aquifer columns showed that this beneficial effect could be eclipsed by an ethanol-driven depletion of electron acceptors, which significantly inhibited BTEX degradation and is probably the most important mechanism by which ethanol could hinder BTEX natural attenuation. A decrease in natural attenuation could increase the likelihood that BTEX compounds reach a receptor as well as the potential duration of exposure.     

Rheumatology trials: selection of adequate response variables and their evaluation

Response variables in rheumatology trials should describe not only the disease manifestations, but should also measure the changes of impairment, disability and handicap. One should use the following criteria, at least: analogue pain scale, score of patient's overall well-being, functional score (A.R.A., Ritchie or Keitel) and Arthritis Impact Measurement Scale (A.I.M.S.). The statistical evaluation of these time-dependent measurements should be done with nonparametric methods using all information over time.     

Kinetics of benzene biodegradation by Pseudomonas aeruginosa: parameter estimation

This study determined the model parameters describing biodegradation of benzene by conducting kinetic microcosm batch tests in both pure solution and saturated aquifer material conditions for various initial benzene (100-700 mg/L) and microbial concentrations (10(7)-10(9) colony-forming units [CFU]/ml) using Pseudomonas aeruginosa as benzene-degrading bacteria. In both tests, benzene and microbial concentrations were monitored over time in order to investigate which of two Monod kinetic equations, the Monod-with-growth or the Monod-no-growth model, was more suitable for describing benzene biodegradation and to estimate the associated model parameters. Parameter estimation was performed by fitting the numerical solution of each model obtained by the fourth-order Runge-Kutta integration to the measured data of benzene and/or microbial concentrations. For the Monod-with-growth model, the best fit of the numerical solution was significantly different than the measured benzene concentrations, especially at early times, because of the gradual increase of microbial population in the growth curve. In contrast, the solution based on the Monod-no-growth model produced reasonable agreement with the measured benzene data. The estimated parameters of maximum substrate utilization rate (kmax) and half-saturation constant (Kc) were in the range of 61 to 105 mg/L/d and about 270 mg/L, respectively, which differ significantly from values previously reported in the literature. We attribute the differences observed in our study to our experimental conditions of initial substrate and bacterial concentrations and oxygen and nutrient supply. Our results imply that an appropriate model type and reasonable values of kinetic parameters should be chosen to model the biodegradation of hydrocarbons in the subsurface environment.