The Experts below are selected from a list of 28269 Experts worldwide ranked by ideXlab platform
David W Graham - One of the best experts on this subject based on the ideXlab platform.
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abundance of six tetracycline resistance genes in wastewater Lagoons at cattle feedlots with different antibiotic use strategies
2007Co-Authors: Nicholas Peak, Charles W Knapp, Richard K Yang, Margery M Hanfelt, Marilyn S Smith, David W GrahamAbstract:The abundance of six tetracycline resistance genes tet(O), tet(Q), tet(W), tet(M), tet(B) and tet(L), were quantified over time in wastewater Lagoons at concentrated animal feeding operations (CAFO) to assess how feedlot operation affects resistance genes in downstream surface waters. Eight Lagoons at five cattle feedlots in the Midwestern United States were monitored for 6 months. Resistance and 16S-rRNA gene abundances were quantified using real-time PCR, and physicochemical lagoon conditions, tetracycline levels, and other factors (e.g. feedlot size and weather conditions) were monitored over time. Lagoons were sorted according to antibiotic use practice at each site, and designated as 'no-use', 'mixed-use' or 'high-use' for comparison. High-use Lagoons had significantly higher detected resistance gene levels (tet(R); 2.8 x 10(6) copies ml(-1)) relative to no-use Lagoons (5.1 x 10(3) copies ml(-1); P < 0.01) and mixed-use Lagoons (7.3 x 10(5) copies ml(-1); P = 0.076). Bivariate correlation analysis on pooled data (n = 54) confirmed that tet(R) level strongly correlated with feedlot area (r = 0.67, P < 0.01) and 'total' bacterial 16S-rRNA gene level in each lagoon (r = 0.51, P < 0.01), which are both characteristic of large CAFOs. tet(M) was the most commonly detected gene, both in absolute number and normalized to 16S-rRNA gene level, although tet(O), tet(Q) and tet(W) levels were also high in the mixed and high-use Lagoons. Finally, resistance gene levels were highly seasonal with abundances being 10-100 times greater in the autumn versus the summer. Results show that antibiotic use strategy strongly affects both the abundance and seasonal distribution of resistance genes in associated Lagoons, which has implications on water quality and feedlot management practices.
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quantification of tetracycline resistance genes in feedlot Lagoons by real time pcr
2004Co-Authors: Marilyn S Smith, Nicholas Peak, Charles W Knapp, Richard K Yang, Margery M Hanfelt, John C Galland, David W GrahamAbstract:A new real-time PCR method is presented that detects and quantifies three tetracycline resistance (Tcr) genes [tet(O), tet(W), and tet(Q)] in mixed microbial communities resident in feedlot lagoon wastewater. Tcr gene real-time TaqMan primer-probe sets were developed and optimized to quantify the Tcr genes present in seven different cattle feedlot Lagoons, to validate the method, and to assess whether resistance gene concentrations correlate with free-tetracycline levels in lagoon waters. The method proved to be sensitive across a wide range of gene concentrations and provided consistent and reproducible results from complex lagoon water samples. The log10 of the sum of the three resistance gene concentrations was correlated with free-tetracycline levels (r2 = 0.50, P 1.95 μg/liter by enzyme-linked immunosorbent assay techniques) than in below-median lagoon samples. Of the three Tcr genes tested, tet(W) and tet(Q) were more commonly found in lagoon water samples. Successful development of this real-time PCR assay will permit other studies quantifying Tcr gene numbers in environmental and other samples.
Nicholas Peak - One of the best experts on this subject based on the ideXlab platform.
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abundance of six tetracycline resistance genes in wastewater Lagoons at cattle feedlots with different antibiotic use strategies
2007Co-Authors: Nicholas Peak, Charles W Knapp, Richard K Yang, Margery M Hanfelt, Marilyn S Smith, David W GrahamAbstract:The abundance of six tetracycline resistance genes tet(O), tet(Q), tet(W), tet(M), tet(B) and tet(L), were quantified over time in wastewater Lagoons at concentrated animal feeding operations (CAFO) to assess how feedlot operation affects resistance genes in downstream surface waters. Eight Lagoons at five cattle feedlots in the Midwestern United States were monitored for 6 months. Resistance and 16S-rRNA gene abundances were quantified using real-time PCR, and physicochemical lagoon conditions, tetracycline levels, and other factors (e.g. feedlot size and weather conditions) were monitored over time. Lagoons were sorted according to antibiotic use practice at each site, and designated as 'no-use', 'mixed-use' or 'high-use' for comparison. High-use Lagoons had significantly higher detected resistance gene levels (tet(R); 2.8 x 10(6) copies ml(-1)) relative to no-use Lagoons (5.1 x 10(3) copies ml(-1); P < 0.01) and mixed-use Lagoons (7.3 x 10(5) copies ml(-1); P = 0.076). Bivariate correlation analysis on pooled data (n = 54) confirmed that tet(R) level strongly correlated with feedlot area (r = 0.67, P < 0.01) and 'total' bacterial 16S-rRNA gene level in each lagoon (r = 0.51, P < 0.01), which are both characteristic of large CAFOs. tet(M) was the most commonly detected gene, both in absolute number and normalized to 16S-rRNA gene level, although tet(O), tet(Q) and tet(W) levels were also high in the mixed and high-use Lagoons. Finally, resistance gene levels were highly seasonal with abundances being 10-100 times greater in the autumn versus the summer. Results show that antibiotic use strategy strongly affects both the abundance and seasonal distribution of resistance genes in associated Lagoons, which has implications on water quality and feedlot management practices.
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quantification of tetracycline resistance genes in feedlot Lagoons by real time pcr
2004Co-Authors: Marilyn S Smith, Nicholas Peak, Charles W Knapp, Richard K Yang, Margery M Hanfelt, John C Galland, David W GrahamAbstract:A new real-time PCR method is presented that detects and quantifies three tetracycline resistance (Tcr) genes [tet(O), tet(W), and tet(Q)] in mixed microbial communities resident in feedlot lagoon wastewater. Tcr gene real-time TaqMan primer-probe sets were developed and optimized to quantify the Tcr genes present in seven different cattle feedlot Lagoons, to validate the method, and to assess whether resistance gene concentrations correlate with free-tetracycline levels in lagoon waters. The method proved to be sensitive across a wide range of gene concentrations and provided consistent and reproducible results from complex lagoon water samples. The log10 of the sum of the three resistance gene concentrations was correlated with free-tetracycline levels (r2 = 0.50, P 1.95 μg/liter by enzyme-linked immunosorbent assay techniques) than in below-median lagoon samples. Of the three Tcr genes tested, tet(W) and tet(Q) were more commonly found in lagoon water samples. Successful development of this real-time PCR assay will permit other studies quantifying Tcr gene numbers in environmental and other samples.
Marilyn S Smith - One of the best experts on this subject based on the ideXlab platform.
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abundance of six tetracycline resistance genes in wastewater Lagoons at cattle feedlots with different antibiotic use strategies
2007Co-Authors: Nicholas Peak, Charles W Knapp, Richard K Yang, Margery M Hanfelt, Marilyn S Smith, David W GrahamAbstract:The abundance of six tetracycline resistance genes tet(O), tet(Q), tet(W), tet(M), tet(B) and tet(L), were quantified over time in wastewater Lagoons at concentrated animal feeding operations (CAFO) to assess how feedlot operation affects resistance genes in downstream surface waters. Eight Lagoons at five cattle feedlots in the Midwestern United States were monitored for 6 months. Resistance and 16S-rRNA gene abundances were quantified using real-time PCR, and physicochemical lagoon conditions, tetracycline levels, and other factors (e.g. feedlot size and weather conditions) were monitored over time. Lagoons were sorted according to antibiotic use practice at each site, and designated as 'no-use', 'mixed-use' or 'high-use' for comparison. High-use Lagoons had significantly higher detected resistance gene levels (tet(R); 2.8 x 10(6) copies ml(-1)) relative to no-use Lagoons (5.1 x 10(3) copies ml(-1); P < 0.01) and mixed-use Lagoons (7.3 x 10(5) copies ml(-1); P = 0.076). Bivariate correlation analysis on pooled data (n = 54) confirmed that tet(R) level strongly correlated with feedlot area (r = 0.67, P < 0.01) and 'total' bacterial 16S-rRNA gene level in each lagoon (r = 0.51, P < 0.01), which are both characteristic of large CAFOs. tet(M) was the most commonly detected gene, both in absolute number and normalized to 16S-rRNA gene level, although tet(O), tet(Q) and tet(W) levels were also high in the mixed and high-use Lagoons. Finally, resistance gene levels were highly seasonal with abundances being 10-100 times greater in the autumn versus the summer. Results show that antibiotic use strategy strongly affects both the abundance and seasonal distribution of resistance genes in associated Lagoons, which has implications on water quality and feedlot management practices.
-
quantification of tetracycline resistance genes in feedlot Lagoons by real time pcr
2004Co-Authors: Marilyn S Smith, Nicholas Peak, Charles W Knapp, Richard K Yang, Margery M Hanfelt, John C Galland, David W GrahamAbstract:A new real-time PCR method is presented that detects and quantifies three tetracycline resistance (Tcr) genes [tet(O), tet(W), and tet(Q)] in mixed microbial communities resident in feedlot lagoon wastewater. Tcr gene real-time TaqMan primer-probe sets were developed and optimized to quantify the Tcr genes present in seven different cattle feedlot Lagoons, to validate the method, and to assess whether resistance gene concentrations correlate with free-tetracycline levels in lagoon waters. The method proved to be sensitive across a wide range of gene concentrations and provided consistent and reproducible results from complex lagoon water samples. The log10 of the sum of the three resistance gene concentrations was correlated with free-tetracycline levels (r2 = 0.50, P 1.95 μg/liter by enzyme-linked immunosorbent assay techniques) than in below-median lagoon samples. Of the three Tcr genes tested, tet(W) and tet(Q) were more commonly found in lagoon water samples. Successful development of this real-time PCR assay will permit other studies quantifying Tcr gene numbers in environmental and other samples.
Carles Ibanez - One of the best experts on this subject based on the ideXlab platform.
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influence of salinity regime on the food web structure and feeding ecology of fish species from mediterranean coastal Lagoons
2014Co-Authors: Patricia Prado, Carolina Vergara, Nuno Caiola, Carles IbanezAbstract:Abstract Dual δ 15 N and δ 13 C analyses and estimates of biomass were used to characterize the food webs of valuable fish species in three coastal Lagoons of the Ebro Delta subjected to contrasting salinity regimes (polyhaline in the Tancada lagoon, mesohaline in the Encanyissada and oligohaline in the Clot lagoon). The δ 13 C signatures of the entire food-web including primary producers, sediment organic matter and consumers showed the most enriched values in the Tancada lagoon (from approx. −4.8‰ in sediments to −19.7‰ in fish) and the most depleted ones in the Clot lagoon (from approx. −11.4‰ in sediments to −25.4‰ in fish), consistent with dominant contributions from marine and continental sources, respectively. For δ 15 N, particularly high values were detected in the submersed vegetation (11.3 ± 0.3‰) together with more enriched sediment values at lower salinities (by approx. 2.5‰), suggesting that historical loadings of agricultural fertilizers are still retained by the systems and transmitted across trophic levels. Negative relationships between δ 15 N and salinity were also observed for the amphipod Gammarus aequicauda and the isopod Sphaeroma hookeri , suggesting some consumption of accumulated and resuspended detrital material. In contrast, δ 15 N signatures of fish showed lower values and inconsistent patterns, possibly because most species have a seasonal use of the Lagoons. The biomass of fish species did not show a clear effect of the salinity regime (except for the mosquitofish Gambusia holbrookii ), but results for mixing models suggest a diet shift from higher contribution of zooplankton size fractions in the Encanyissada (from 57 to 73%) to macrofauna at the other Lagoons (from 40 to 67%). We suggest that alterations in salinity might modify the trophic dynamics of the systems from benthic to planktonic pathways, without large-scale differences in δ 15 N of fish suggestive of similar trophic levels.
Alice Newton - One of the best experts on this subject based on the ideXlab platform.
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do physiography and hydrology determine the physico chemical properties and trophic status of coastal Lagoons a comparative approach
2013Co-Authors: Leonilde Roselli, Miguel Canedoarguelles, Costa P Goela, Sonia Cristina, Maria Rieradevall, Raffaele Dadamo, Alice NewtonAbstract:Coastal Lagoons are very heterogeneous systems covering a wide range of physiographical and hydrological characteristics. The hypothesis of the present investigation was that physiographical and hydrological characteristics of coastal Lagoons affect their physico-chemical properties and their buffering capacity against nutrient enrichment. We compared data collected during a complete annual cycle in six coastal Lagoons which were representative of the different lagoon types proposed by Kjerfve (1986) and were subjected to different anthropogenic pressures. The greater exchange of water with the sea in the leaky lagoon of Ria Formosa (type 3) reduced the seasonal differences in the physico-chemical variables and increased the buffer capacity against nutrient enrichment when compared to the restricted (type 2) and chocked (type 1) lagoon types. The lagoon types also showed important differences regarding nutrient limitation, with types 1 and 2 being P-limited and type 3 being N-limited. Our approach can be applied to other coastal Lagoons representative of transitional water types in order to provide a general framework for the rational management and policy strategies of coastal Lagoons.
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does microphytobenthos resuspension influence phytoplankton in shallow systems a comparison through a fourier series analysis
2012Co-Authors: Ana C Brito, Alice Newton, Teresa F Fernandes, Chiara Facca, Paul TettAbstract:Abstract Shallow coastal Lagoons, especially the ones with clear waters and lighted substrata, are likely to have large microphytobenthos (MPB) communities. MPB is an important component of these systems, representing up to 99% of the chlorophyll concentration when compared to phytoplankton. It is therefore expected that MPB resuspension play a key role in the dynamics of phytoplankton due to the tide and wind action. Water samples were collected twice per month inside and outside Ria Formosa lagoon (Portugal), for nutrients and chlorophyll a (chl a). Sediment samples were also collected for MPB chl a . Chl a was also analysed in water and sediment samples from Venice lagoon (Italy), at least once per month. A truncated Fourier series was fitted to the data to investigate the seasonal and high-frequency components of the time-series. In the Ria Formosa, the best significant fit for MPB was obtained considering the sum of 26 wave-pairs (sin and cosine), which explained 31% of the variability. The seasonal cycle (1–3 waves) explained approximately 5% of the total variability. Within-day variability which includes spatial heterogeneity explained 61% of the variability. The best fit for phytoplankton inside Ria Formosa was obtained considering the sum of 23 wave-pairs. Outside the lagoon the best fit was obtained using only the sum of 16 wave-pairs. For both cases, the sum of waves explained more than 64% of the variability and the seasonal cycle explained more than 31% of the variability. It is expected that primary producers in the water column have a strong seasonal factor due to the direct effect of the solar cycle, which is the case of other clear waters. In the Venice lagoon, which is microtidal, the best fit for MPB was obtained using 10 wave-pairs. However, the best fit for phytoplankton was obtained with only 3 wave-pairs, indicating the importance of the seasonal cycle. Significant relationships were found between phytoplankton inside and outside the Ria Formosa, as well as between microphytobenthos and phytoplankton in the Lagoons of Venice and Ria Formosa. These results suggest the influence of MPB resuspension in the phytoplankton community of shallow coastal Lagoons and the importance of phytoplankton exportation to the coastal zone.
