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Ronholm J.,Microbiology Research Division | Petronella N.,Bureau of Food Surveillance and Science Integration | Chew Leung C.,Microbiology Research Division | Chew Leung C.,Pest Management Regulatory Agency | And 2 more authors.
Applied and Environmental Microbiology | Year: 2016

Vibrio parahaemolyticus is a bacterial pathogen that can cause illness after the consumption or handling of contaminated seafood. The primary virulence factors associated with V. parahaemolyticus illness are thermostable direct hemolysin (TDH) and Tdh-related hemolysin (TRH). However, clinical strains lacking tdh and trh have recently been isolated, and these clinical isolates are poorly understood. To help understand the emergence of clinical tdh- and trh-negative isolates, a genomic approach was used to comprehensively compare 4 clinical tdh- and trh-negative isolates with 16 environmental tdh- and trh-negative isolates and 34 clinical isolates positive for tdh or trh, or both, with the objective of identifying genomic features that are unique to clinical tdh- and trh-negative isolates. The prevalence of pathogenicity islands (PAIs) common to clinical isolates was thoroughly examined in each of the clinical tdh- and trh-negative isolates. The tdh PAI was not present in any clinical or environmental tdhand trh-negative isolates. The trh PAI was not present in any environmental isolates; however, in clinical tdh- and trh-negative isolate 10-4238, the majority of the trh PAI including a partial trh1 gene was present, which resulted in reclassification of this isolate as a tdh-negative and trh-positive isolate. In the other clinical tdh- and trh-negative isolates, neither the trh gene nor the trh PAI was present. We identified 862 genes in clinical tdh- and trh-negative isolates but not in environmental tdh- and trh-negative isolates. Many of these genes are highly homologous to genes found in common enteric bacteria and included genes encoding a number of chemotaxis proteins and a novel putative type VI secretion system (T6SS) effector and immunity protein (T6SS1). The availability of genome sequences from clinical V. parahaemolyticus tdh- and trh-negative isolates and the comparative analysis may help provide an understanding of how this pathotype is able to survive in vivo during clinical illness. © 2016, American Society for Microbiology. Source


Thomas A.G.,Agriculture and Agri Food Canada | Legere A.,Agriculture and Agri Food Canada | Leeson J.Y.,Agriculture and Agri Food Canada | Stevenson F.C.,142 Rogers Road | And 2 more authors.
Weed Research | Year: 2011

Contrasting approaches to integrated weed management (IWM) for prairie cropping systems were evaluated by measuring weed response to six IWM systems in a wheat-oilseed rape-barley-pea rotation at Saskatoon and Watrous, Saskatchewan, Canada. The six IWM systems (high herbicide/zero tillage; medium herbicide/zero tillage; low herbicide/zero tillage; low herbicide/low tillage; medium herbicide/medium tillage; no herbicide/high tillage) included various combinations of seeding rate and date, herbicide timing and rate, and tillage operations, in order to achieve similar weed management levels. Changes in weed communities were assessed over 4 years by monitoring species composition and abundance at various times during the growth season. Principal response curves indicated a gradual increase in Thlaspi arvense, Chenopodium album, Amaranthus retroflexus and Fallopia convolvulus in the no herbicide/high tillage system. Winter and early spring annuals and perennials increased in most systems, but particularly in the low herbicide/zero tillage and medium herbicide/zero tillage systems. Although five of the six IWM systems provided similar results, changes in weed communities would suggest that operations could be revised to improve the overall management of certain weed species and reduce seed return in the no herbicide/high tillage system and in systems with low herbicide inputs and zero tillage. This study confirms the potential of contrasting IWM systems under the challenging environmental conditions of the Canadian Prairies. © 2010 Agriculture and Agri-Food Canada. Weed Research © 2010 European Weed Research Society. Source


Jeen S.-W.,University of Waterloo | Yang Y.,University of Waterloo | Gui L.,University of Waterloo | Gui L.,Pest Management Regulatory Agency | Gillham R.W.,University of Waterloo
Journal of Contaminant Hydrology | Year: 2013

Column experiments and numerical simulations were conducted to evaluate the effects of Cr(VI) and dissolved CaCO3 on the iron reactivity towards trichloroethene (TCE) and Cr(VI) reduction. Column experiments included measurements of iron corrosion potential and characterization of surface film composition using Raman spectroscopy. Three columns received different combinations of TCE (5 mg L- 1), Cr(VI) (10 mg L- 1) and dissolved CaCO3 (300 mg L- 1), after short periods of conditioning with Millipore water followed by 10 mg L- 1 TCE in Millipore water, for a total of 8 months. The results showed that co-existence with TCE did not affect Cr(VI) reduction kinetics, however, the presence of Cr(VI) reduced TCE degradation rates significantly. The formation of Fe(III)/Cr(III) products caused progressive passivation of the iron and was consistent with the increase in corrosion potential. The presence of dissolved CaCO3 resulted in a stable corrosion potential and faster degradation rates of TCE and Cr(VI). Over time, however, the accumulation of secondary carbonate minerals on the iron surface decreased the iron reactivity. Numerical simulation using a reactive transport model reproduced the observations from the column experiments reasonably well. The simulation can be valuable in the design of PRBs or in the development of effective maintenance procedures for PRBs treating groundwater co-contaminated with Cr(VI) and TCE in the presence of dissolved CaCO3. © 2012 Elsevier B.V. Source


Jeen S.-W.,Chonbuk National University | Lazar S.,Consulting Inc. | Gui L.,Pest Management Regulatory Agency | Gillham R.W.,University of Waterloo
Journal of Contaminant Hydrology | Year: 2014

Degradation of trichlorofluoromethane (CFC11) and 1,1,2-trichloro-1,2,2- trifluoroethane (CFC113) by granular iron and bimetallic (nickel- or palladium-enhanced) irons was studied in flow-through column tests. Both compounds were rapidly degraded, following pseudo-first-order kinetics with respect to the parent compounds. The average pseudo-first-order rate constants for CFC11 were similar among different materials, except for palladium-enhanced iron (PdFe), in which the rate of degradation was about two times faster than for the other materials. In the case of CFC113, the rate constants for bimetallic irons were about two to three times greater than for the regular iron material. The smaller than expected differences in degradation rate constants of chlorofluorocarbons (CFCs) between regular iron and bimetallic irons suggested little, if any, catalytic effect of the bimetallic materials in the initial degradation step. Subsequent degradation steps involved catalytic hydrogenation, however, playing a significant role in further degradation of reaction intermediates. The degradation intermediates and final products of CFC11 and CFC113 suggested that degradation proceeded through hydrogenolysis and α/β-elimination in the presence of regular iron (Fe) and nickel-enhanced iron (NiFe). Even though there is only minor benefit in the use of bimetallic iron in terms of degradation kinetics of the parent CFCs, enhanced degradation rates of intermediates such as chlorotriflouroethene (CTFE) in subsequent reaction steps could be beneficial. © 2014 Elsevier B.V. Source


Mineau P.,Carleton University | Whiteside M.,Carleton University | Whiteside M.,Pest Management Regulatory Agency
PLoS ONE | Year: 2013

Common agricultural birds are in decline, both in Europe and in North America. Evidence from Europe suggests that agricultural intensification and, for some species, the indirect effects of pesticides mediated through a loss of insect food resource is in part responsible. On a state-by-state basis for the conterminous Unites States (U.S.), we looked at several agronomic variables to predict the number of grassland species increasing or declining according to breeding bird surveys conducted between 1980 and 2003. Best predictors of species declines were the lethal risk from insecticide use modeled from pesticide impact studies, followed by the loss of cropped pasture. Loss of permanent pasture or simple measures of agricultural intensification such as the proportion of land under crop or the proportion of farmland treated with herbicides did not explain bird declines as well. Because the proportion of farmland treated with insecticides, and more particularly the lethal risk to birds from the use of current insecticides feature so prominently in the best models, this suggests that, in the U.S. at least, pesticide toxicity to birds should be considered as an important factor in grassland bird declines. © 2013 Mineau, Whiteside. Source

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