A high soil potential net nitrification was observed at 4 m depth: What are the driving factors?

Studies about nitrogen (N) mineralization and nitrification in deep soil layers are rare because N processes are considered to occur mainly in topsoil that hosts active and diverse microbial communities. This study aimed to measure the soil potential net N mineralization (PNM) and nitrification (PNN) down to 4 m depth and to discuss factors controlling their variability. Twenty-one soil cores were collected at the Restinclières agroforestry experimental site, where 14-year-old hybrid walnut trees were intercropped with durum wheat. Soil cores were incubated in the dark in the laboratory at both 6 and 25°C. The soil was a deep calcic fluvisol with a fluctuating water table. It featured a black layer that was very rich in organic matter and permanently water saturated at depths between 3.0 and 4.0 m. The mean soil mineral N content was 3 mg N kg⁻¹ soil in the upper 0.0–0.2 m layer, decreasing until a depth of 2 m and increasing to the maximum value of 25.8 mg N kg⁻¹ soil in the black layer. While nitrate (NO₃⁻) was the dominant form of mineral N (89%) in the upper 0.0–0.2 m layer, its proportion progressively decreased with depth until ammonium (NH₄⁺) became almost the only form of mineral N (97%) in the saturated black layer. Laboratory soil incubation revealed that PNM and PNN occurred at all depths, although the latter remained low at 6°C. The soil nitrate content in the black layer was multiplied by 48 times after 51 days of incubation at 25°C, whereas it was almost inexistent at the sampling date. While the soil total N, the pH and the incubation temperature explained 84% of the variation in PNM, only 29% of the percent nitrification variance was explained by the incubation temperature (T_inc) and the soil C-to-N ratio. These results point out the necessity to consider soil potential net N mineralization and nitrification of deep soil layers to improve model predictions.     

Simultaneous zoonotic transmission of Chlamydophila psittaci genotypes D, F and E/B to a veterinary scientist

Two groups of five 1-day-old conventional turkeys were housed in negative pressure stables to become experimentally infected with Avian Metapneumovirus (aMPV) and Ornithobacterium rhinotracheale (ORT) at the age of 3 weeks. However, during the first 2 weeks, turkeys started to show respiratory disease characterized by rhinitis and dyspnoea. Routine bacterial and viral diagnoses remained negative. Therefore, pharyngeal swabs from the turkeys and from the veterinary scientist handling the animals were examined for the presence of Chlamydophila (C.) psittaci by using a combination of cell culture, nested PCR and ompA genotype-specific quantitative real-time PCR, as well as by serology. Results revealed simultaneous transmission of C. psittaci outer membrane protein A (ompA) genotypes D, F and E/B from infected turkeys to the veterinary scientist.     

The Marek��s disease virus (MDV) protein encoded by the UL17 ortholog is essential for virus growth

Marek’s disease virus type 1 (MDV-1) shows a strict dependency on the direct cell-to-cell spread for its propagation in cell culture. As MDV-1 shows an impaired nuclear egress in cell culture, we wished to address the characterization of capsid/tegument genes which may intervene in the maturation of intranuclear capsids. Orthologs of UL17 are present in all herpesviruses and, in all reported case, were shown to be essential for viral growth, playing a role in capsid maturation and DNA packaging. As only HSV-1 and PrV UL17 proteins have been characterized so far, we wished to examine the role of MDV-1 pUL17 in virus replication. To analyze MDV-1 UL17 gene function, we created deletion mutants or point mutated the open reading frame (ORF) to interrupt its coding phase. We established that a functional ORF UL17 is indispensable for MDV-1 growth. We chose to characterize the virally encoded protein by tagging the 729 amino-acid long protein with a repeat of the HA peptide that was fused to its C-terminus. Protein pUL17 was identified in infected cell extracts as an 82 kDa protein which localized to the nucleus, colocalizing with VP5, the major capsid protein, and VP13/14, a major tegument protein. By using green fluorescent protein fusion and HA tagged proteins expressed under the cytomegalovirus IE gene enhancer/promoter (P_{CMV IE}), we showed that MDV-1 pUL17 nuclear distribution in infected cells is not an intrinsic property. Although our results strongly suggest that another viral protein retains (or relocate) pUL17 to the nucleus, we report that none of the tegument protein tested so far were able to mediate pUL17 relocation to the nucleus.     

Altered pesticide use on transgenic crops and the associated general impact from an environmental perspective

The large-scale commercial cultivation of transgenic crops has undergone a steady increase since their introduction 10 years ago. Most of these crops bear introduced traits that are of agronomic importance, such as herbicide or insect resistance. These traits are likely to impact upon the use of pesticides on these crops, as well as the pesticide market as a whole. Organizations like USDA-ERS and NCFAP monitor the changes in crop pest management associated with the adoption of transgenic crops. As part of an IUPAC project on this topic, recent data are reviewed regarding the alterations in pesticide use that have been observed in practice. Most results indicate a decrease in the amounts of active ingredients applied to transgenic crops compared with conventional crops. In addition, a generic environmental indicator -- the environmental impact quotient (EIQ) -- has been applied by these authors and others to estimate the environmental consequences of the altered pesticide use on transgenic crops. The results show that the predicted environmental impact decreases in transgenic crops. With the advent of new types of agronomic trait and crops that have been genetically modified, it is useful to take also their potential environmental impacts into account.     

Does oxidation affect the water functionality of myofibrillar proteins?

Water-binding properties of myofibrils extracted from porcine muscle, and added hemoglobin with and without exposure to H2O2, were characterized using low-field proton NMR T2 relaxometry. The effects of pH and ionic strength in the samples were investigated as pH was adjusted to 5.4, 6.2, and 7.0 and ionic strength was adjusted to 0.29, 0.46, and 0.71 M, respectively. The formation of dityrosine as a measure of oxidative protein cross-linking revealed a significant increase in dityrosine concentrations upon H2O2 activation. The formation of dityrosine was strongly pH-dependent and increased with decreasing pH. In addition, increased levels of thiobarbituric acid reactive substances were observed upon addition of H2O2, implying that lipid oxidation was enhanced, however, with a different oxidation pattern as compared to the myofibrillar proteins. Low-field NMR relaxation measurements revealed reduced T2 relaxation times upon H2O2 activation, which corresponds to reduced water-holding capacity upon oxidation. However, a direct relationship between degree of oxidation and T2 relaxation time was not observed with various pH values and ionic strengths, and further studies are needed for a complete understanding of the effect of oxidation on myofibrillar functionality.     

Screening of quinalphos,trifluralin and dichlorvos residues in fresh water of aquaculture systems in Mekong Delta,Vietnam

To develop an easy and reliable method for detecting pesticides and their residues in the Mekong Delta, a GC‐MS analytical method was developed and validated according to European guidelines (SANTE/11945/2015) for the determination of residues of three pesticides (quinalphos, trifluralin and dichlorvos) in water. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.002 and 0.007 μg/L, respectively, for quinalphos and trifluralin, and 0.016 and 0.053 μg/L, respectively, for dichlorvos and quinalphos. The repeatability, the within‐laboratory reproducibility as well as the trueness met the European criteria. The recovery rate ranged between 72% (for dichlorvos and quinalphos) and 82% (for trifluralin). The developed method was then applied for the analysis of 33 water samples, collected in April 2013, at the beginning of the rainy season in the Mekong Delta in Vietnam. Thirteen samples were from rice field, 10 were collected from cat fish ponds and from red tilapia cages. Results showed that only 9% of total water samples analysed contained residues of pesticides, but only in water from rice fish systems. From the 13 samples taken in these systems, quinalphos was detected in three samples. The other two pesticides were not detected. A comparison between analytical results obtained from GC‐MS and an alternative method, that is GC‐ECD indicated that GC‐ECD is less sensitive than GC‐MS, with LOQ ranging from 0.37 to 1.18 (depending on the pesticide). However, for samples with concentrations above these LOQ, no significant difference was observed between the results obtained from the two analytical methodologies.     

Environmental variability controls recruitment but with different drivers among spawning components in Gulf of St. Lawrence herring stocks

The factors affecting herring recruitment are still poorly understood, complicating the prediction of stock dynamics and the choice of operational management strategies. We investigated effects of intrinsic (SSB) and extrinsic factors (physical and biological environments, including competition and predation) on recruitment of the spring and fall spawning components of each of the two herring stocks occurring in the Gulf of the St. Lawrence between 1971 and 2014. Effects of potential explanatory factors on recruit (age 2) abundance were tested using Generalized Additive Models. Model fit was significantly improved by incorporating both physical and biological environmental variability, but effects of herring SSB and predation were not significant. Indices of zooplankton abundance and phenology explained more variance in recruitment than physical indices. Our results emphasize the dominance of bottom‐up processes over SSB in the regulation of herring recruitment. Environmental variability did not seem to act uniformly on the recruitment of either stock or their respective spawning components. A long‐term trend of decreasing recruitment in spring spawners was associated with a long‐term decline in abundance of cold water copepods. In fall spawners, optimal recruitment was dependent on warmer environmental conditions combined with an adequate supply (species composition and phenology) of zooplankton. These results provide the first empirical evidence that spring and fall spawning herring are adapted to contrasting environmental conditions and shed light on the potential mechanisms linking herring recruitment to key zooplankton community characteristics and phenology. Management strategies can be improved by incorporating this new knowledge on environmental drivers of herring recruitment.     

Exudative epidermitis and porcine circovirus-2 infection in a Swedish SPF-herd

An outbreak of exudative epidermitis (EE) among piglets in a Swedish SPF-herd initiated a survey for indications as to the cause of disease.The herd was established by caesarean section and has been closed to all new animal material, with the exception of semen for artificial insemination (AI). The study comprised serum samples from the SPF-herd over a 10-year period (n=109) and a close monitoring of animals in the herd during the period after the EE outbreak. Serum samples from conventional boars at the AI-station servicing the herd were also included (n=9). All serum samples were tested for antibodies to porcine circovirus-2 (PCV-2). In addition, 3-week-old piglets from three litters (n=24) farrowed close after the initial EE outbreak were closely monitored for clinical signs of skin disease, sampled for Staphylococcus hyicus, tested for antibodies to porcine parvovirus and in sequentially collected serum samples tested for interferon-alpha (IFN-alpha) and interleukin-6.The PVC-2 serology showed that animals in the herd were sero-negative at least until 2 months prior to the EE outbreak. During the period close after the EE outbreak the animals showed varying levels of antibodies to PCV-2 but all the tested animals had sero-converted 4 months later. The AI boars were also sero-positive to PCV-2 at the time of the EE outbreak. Animals in the SPF-herd remained sero-positive to PCV-2 during the following 7 years. In the monitored litters, one piglet had clinical EE and 15 piglets displayed defined erythemas on the abdomen. Fourteen of the piglets also had IFN-alpha in serum on one or more occasions during the study, indicating viral activity among the animals. S. hyicus was isolated from all of the piglets from the earliest sampling point (3 days of age) and onwards, irrespective of clinical signs. PCV-2 was isolated from lymph node tissue collected from one of the EE affected pigs.Further, increases in the number of stillborn piglets, small litters (<6 piglets) and repeat breeders could be correlated to the time of PCV-2 sero-conversion. Coincidence of active viral infection and sero-conversion to PCV-2 points to the virus as the cause of the EE outbreak and reproductive disturbances.     

Homology modelling of Drosophila cytochrome P450 enzymes associated with insecticide resistance

BACKGROUND: Overexpression of the cytochrome P450 gene Cyp6g1 confers resistance against DDT and a broad range of other insecticides in Drosophila melanogaster Meig. In the absence of crystal structures of CYP6G1 or complexes with its substrates, structural studies rely on homology modelling and ligand docking to understand P450–substrate interactions. RESULTS: Homology models are presented for CYP6G1, a P450 associated with resistance to DDT and neonicotinoids, and two other enzymes associated with insecticide resistance in D. melanogaster, CYP12D1 and CYP6A2. The models are based on a template of the X‐ray structure of the phylogenetically related human CYP3A4, which is known for its broad substrate specificity. The model of CYP6G1 has a much smaller active site cavity than the template. The cavity is also ‘V’‐shaped and is lined with hydrophobic residues, showing high shape and chemical complementarity with the molecular characteristics of DDT. Comparison of the DDT–CYP6G1 complex and a non‐resistant CYP6A2 homology model implies that tight‐fit recognition of this insecticide is important in CYP6G1. The active site can accommodate differently shaped substrates ranging from imidacloprid to malathion but not the pyrethroids permethrin and cyfluthrin. CONCLUSION: The CYP6G1, CYP12D1 and CYP6A2 homology models can provide a structural insight into insecticide resistance in flies overexpressing P450 enzymes with broad substrate specificities. Copyright © 2010 Society of Chemical Industry