Metagenomic and metatranscriptomic analysis reveals enrichment for xenobiotic-degrading bacterial specialists and xenobiotic-degrading genes in a Canadian Prairie two-cell biobed system.

Biobeds are agriculture-based bioremediation tools used to safely contain and microbially degrade on-farm pesticide waste and rinsate, thereby reducing the negative environmental impacts associated with pesticide use. While these engineered ecosystems demonstrate efficient pesticide removal, the microbiomes in these environments remain largely understudied both taxonomically and functionally. This study used metagenomic and metatranscriptomic techniques to characterize the microbial community in a two-cell Canadian biobed system before and after a field season of pesticide application. These culture-independent approaches identified an enrichment of xenobiotic-degrading bacteria, such as Afipia, Sphingopyxis and Pseudomonas, and enrichment and transcription of xenobiotic-degrading genes, such as peroxidases, oxygenases, and hydroxylases, among others; we were able to directly link the transcription of these genes to Pseudomonas, Oligotropha, Mesorhizobium, Rhodopseudomonas, and Stenotrophomonas taxa.

Evaluation of interactive effects of UV light and nano encapsulation on the toxicity of azoxystrobin on zebrafish.

The use of nanotechnology to enhance pesticide formulations holds the promise of reduced pesticide use, reduced mobility in soils, and overall improvements in agricultural practices while simultaneously maintaining yields. However, the toxicity of nano-enabled pesticides, including azoxystrobin (Az), has not been well studied compared with their conventional form. This study investigates both lethal and sub-lethal endpoints in zebrafish embryos up to 120 h post-fertilization (hpf) under either laboratory light or simulated UV light. The median lethal concentration (LC50) value of nano-enabled Az (nAz) was significantly lower than the conventional form (Az). Interestingly, artificial UV light significantly increased toxicity (decreased LC50) of both Az and nAz. Malformations were not observed but the remaining yolk sac volume was significantly increased in both types of Az at both light conditions. This decreased yolk consumption is in agreement with reduced oxygen consumption and heart rate. Catalase enzyme activity was only reduced to UV light while superoxide dismutase activity was significantly reduced by co-exposure of UV light, and either type of Az at a nominal concentration of 100 µg L-1. The co-exposure of Az at 100 µg L-1 and UV light significantly upregulated sod1, sod2, and gpx1b expression and both types of Az significantly reduced gpx1a expression. Lipid peroxidation was significantly increased in nAz and Az at 100 µg L-1 under laboratory light, while UV light induced even higher level of lipid peroxidation. The results will provide important information on the toxicity of nAz under ecologically realistic conditions.

Auxin Herbicides and Pesticide Mixtures in Groundwater of a Canadian Prairie Province.

Groundwater samples were collected from piezometers and water table wells in both dryland and irrigated agricultural regions of Alberta, Canada, to examine the occurrence of pesticide mixtures. Fourteen current-use pesticides and two historical compounds were detected over a 3-yr sampling period. Pesticide mixtures were detected in ∼3% of the groundwater samples, and the frequency of detection increased from spring (1.5%) to summer (3.8%) and fall (4.8%). Pesticide mixtures always consisted of at least one of two auxin herbicides: 2,4-dichlorophenoxyacetic acid (2,4-D) or 2-methyl-4-chlorophenoxyacetic acid (MCPA). 19% of all samples contained a single pesticide, with auxin herbicides 2,4-D (7.3%), MCPA (4.4%), and clopyralid (3.9%) being most prevalent. We detected 2,4-D predominantly in the fall (72% of 2,4-D detections) and less in spring and summer (28%). We detected MCPA mostly in summer (85% of MCPA detections) and less in spring and fall (15%). Clopyralid was more evenly detected across spring (30%), summer (25%), and fall (45%). Since the auxin herbicides above are typically applied in summer, results suggest that each herbicide may have different mobility and persistence characteristics in prairie soils. Guidelines for Canadian Drinking Water Quality have been set for a range of individual pesticides, but not for pesticide mixtures. If Canada is to establish such guidelines, this study demonstrates that auxin herbicides should be prioritized. In addition, only 7 of the 16 compounds detected in this study have established maximum acceptable concentrations (MACs), excluding clopyralid, which was detected in all three sampling years.

Development of a real-time immuno-PCR assay for the quantification of 17ß-estradiol in water.

A competitive real-time (RT) immuno-polymerase chain reaction (iPCR) (RT-iPCR) assay was developed for the sensitive quantification of 17ß-estradiol in water. Using a universal iPCR method and polyclonal antibodies, 17ß-estradiol was accurately quantified at concentrations ranging from 1 pg mL(-1) to 10 µg mL(-1). The RT-iPCR assay's limit of detection was 0.7 pg mL(-1). The RT-iPCR assay provided an 800-fold increase in sensitivity as well as an expanded working range compared with the corresponding enzyme-linked immunosorbent assay. Assay cross-reactivity to estrone and estriol, two structurally related estrogens, was below 8%. Water samples spiked with 17ß-estradiol were analyzed by RT-iPCR to determine the assay's potential as a rapid screen for the monitoring of manure-borne estrogens in the environment. The assay showed recoveries of 82, 102 and 103% for Milli-Q, tap, and irrigation water, respectively, without requiring sample extraction or concentration prior to analysis.