Effects of silver nanoparticle size, concentration and coating on soil quality as indicated by arylsulfatase and sulfite oxidase activities

Recently, the nanotechnology industry has seen a growing interest in integrating silver nanoparticles (AgNPs) into agricultural products, which increases soil exposure to these particles. This demands an investigation into the effect of AgNPs on soil health. Changes in soil enzyme activities upon exposure to AgNPs can serve as early indicators of any adverse effects that these particles may have on soil quality. This study aimed to determine the effects of AgNP size, concentration, coating, and exposure time on the activities of two sulfur cycle enzymes, arylsulfatase and sulfite oxidase. To investigate the sensitivity of soil enzyme activity to AgNP contamination, silt loam soil samples were treated with 30, 80, and 200 nm-sized AgNPs coated with citrate, lipoic acid, and polyvinylpyrrolidone at 1, 10, and 100 mg Ag kg^-1 soil, with the changes in enzyme activities monitored at 3 h, 3 d, and 30 d after treatment. For comparison, the effects of silver (Ag) ions on the enzyme activities were studied under similar treatment conditions. For most of the concentrations tested, the inhibitory effects of AgNPs on different enzymes differed, with a much stronger effect on sulfite oxidase activity than on arylsulfatase activity. The AgNP concentration and exposure time played much important roles than coating type and particle size in the effects of AgNPs on soil enzyme activities.     

Organoleptic research in the interests of Horticultural Plant Breeding

One of the many characters for which new breeding products are tested at the Institute of Horticultural Plant Breeding, Wageningen, is the consumption quality. This can only be properly done if suitable methods and experienced tasters are available.Some known organoleptic methods are described, together with their objectives. As the trials at the above Institute were mainly carried out to analyse the flavour of various selections or varieties of certain crops, the method of the analytical appraisal found the widest application. It is described in this paper.Members of staff were tested for tasting ability and selected with the aid of the four basic tastes (sweet, sour, salt, bitter) and aroma.The method of preparing and serving the samples, as well as some typical experiences gained with a number of crops are briefly summarized.     

The solidity of the cauliflower curd

Research has been carried out on the inheritance of the solidity of the cauliflower curd. Assuming that this character depends on a number of polygenic factors, the occurring segregations could be explained. Plants with the same solidity may be of a highly different genetic nature, and in propagation may segregate very differently.During selection proper attention should be paid to the solidity of the curds, the more so as loose plants propagate more rapidly.     

The long-term preservation of potato virus Y and watermelon mosaic virus in liquid nitrogen in comparison to other preservation methods

Samples of watermelon mosaic virus (WMMV), consisting of clarified sap of diseased squash plants, were found to be very infective after more than 4 years of storage if the samples had been deep frozen at –18°C, and to have lost most of their infectivity within 4 years of preservation by freeze drying and subsequent storage of the samples at 4°C.Potato virus Y (PVY) inocula, consisting of samples of clarified sap of diseased red peppers, lost their infectivity in less than 4 years if the samples had been deep frozen at –18°C but retained their infectivity for more than 4 years if the samples had been freeze dried and stored at 4°C.A decrease in infectivity of both viruses in the deep frozen at –18°C and freeze dried inocula could be observed even during the first months of storage. However, samples of clarified sap stored in or over liquid nitrogen maintained their activity for at least 22 months for WMMV and 32 months for PVY with no indication of a decrease in infectivity of the viruses. Storage in or over liquid nitrogen seems therefore a very promising long-term preservation method for plant viruses.Samenvatting Watermeloenmozaïekvirus inocula, bestaande uit helder gecentrifugeerd sap van zieke squashplanten, bleken hun infectievermogen zeer goed te hebben behouden na meer dan vier jaar bewaring bij –18°C, maar binnen vier jaar grotendeels te hebben verloren na droogvriezen en bewaren bij 4°C.Overeenkomstig bereide aardappelvirus Y inocula uit zieke paprikaplanten hadden hun infectievermogen binnen vier jaar verloren na bewaring bij –18°C, maar konden hun infectievermogen grotendeels behouden gedurende meer dan vier jaar na droogvriezen en bewaring bij 4°C.Binnen enkele maanden na het begin der bewaringsperiode kon al een afname van het infectievermogen van beide virussen in de diepgevroren (–18°C) en drooggevroren inocula worden gevonden. Helder gecentrifugeerde sapmonsters die in of boven vloeibare stikstof bewaard waren, hadden gedurende tenminste 22 maanden voor het watermeloenmozaïekvirus en 32 maanden voor het aardappelvirus Y hun volle infectievermogen behouden. Bewaring in of boven vloeibare stikstof is daarom de beste van de drie getoetste bewaarmethodes voor opslag op lange termijn van beide virussen. Deze methode lijkt ook veelbelovend voor een groot aantal andere virussen.     

A proposed method of polyacrylamide gel electrophoresis in acid environments applied to gliadins of wheat grains

Summary In this paper we describe the method of wheat gliadin electrophoresis in use at RIVRO, Wageningen. It differs from other techniques mainly by the application of an alternative buffer system, making it possible to polymerise the gels in a buffered alkaline environment and to perform the run at pH 3.1 without extensive buffer changing steps. Advantages are a greater gel reproducibility and the ease of gel handling. Furthermore, a rationalised protein extraction procedure, a cheap shaking system for staining baths and a better (slower moving) tracking dye are described.     

Internal tipburn in white cabbage II. The effect of some environmental factors

1. 1.
   Early planting, late harvesting and a heavy dressing of nitrogen favour the occurrence of tipburn in white cabbage.     

A stochastic single-molecule event triggers phenotype switching of a bacterial cell

By monitoring fluorescently labeled lactose permease with single-molecule sensitivity, we investigated the molecular mechanism of how an Escherichia coli cell with the lac operon switches from one phenotype to another. At intermediate inducer concentrations, a population of genetically identical cells exhibits two phenotypes: induced cells with highly fluorescent membranes and uninduced cells with a small number of membrane-bound permeases. We found that this basal-level expression results from partial dissociation of the tetrameric lactose repressor from one of its operators on looped DNA. In contrast, infrequent events of complete dissociation of the repressor from DNA result in large bursts of permease expression that trigger induction of the lac operon. Hence, a stochastic single-molecule event determines a cell's phenotype.     

Effects of Silver Nanoparticles on the Activities of Soil Enzymes Involved in Carbon and Nutrient Cycling

Soils are continuously exposed to large amounts of engineered nanoparticles, especially silver nanoparticles (AgNPs), which can affect the activity, stability, and specificity of microbial enzymes. Therefore, the measurement of specific enzyme activity can be used to identify major changes in soil environments. Accordingly, the aim of the present study was to investigate the effects of AgNPs on soil enzymes that play critical roles in mineralizing carbon and nutrients in soil. Soil samples (silt loam and sandy loam) were collected from the surface layer (0–15 cm) of a field at the George Washington Carver Farm, Lincoln University of Missouri, USA. The soils were then treated with AgNP solutions at 0, 1 600, or 3 200 μg Ag kg~(-1) dry soil, using either 10- or 50-nm AgNPs and a randomized complete block design, with three replicates per treatment. The AgNP-treated soil samples were homogenized and incubated for one month, and soil acid phosphatase, β-glucosaminidase, β-glucosidase, and arylsulfatase activities were measured after one hour, one week, and one month of incubation. The activities of all four enzymes were reduced by AgNP treatment after one hour and one week.However, AgNP size had no effect. After one month of incubation, the AgNP treatments had mixed effects, which suggests that soil enzymes are only affected on a short-term basis. Further studies are required to determine the mechanisms by which AgNPs reduce soil enzyme activity.     

A defined intestinal colonization microbiota for gnotobiotic pigs

Maximising the ability of piglets to survive exposure to pathogens is essential to reduce early piglet mortality, an important factor in efficient commercial pig production. Mortality rates can be influenced by many factors, including early colonization by microbial commensals. Here we describe the development of an intestinal microbiota, the Bristol microbiota, for use in gnotobiotic pigs and its influence on synthesis of systemic immunoglobulins. Such a microbiota will be of value in studies of the consequences of early microbial colonization on development of the intestinal immune system and subsequent susceptibility to disease. Gnotobiotic pig studies lack a well-established intestinal microbiota. The use of the Altered Schaedler Flora (ASF), a murine intestinal microbiota, to colonize the intestines of Caesarean-derived, gnotobiotic pigs prior to gut closure, resulted in unreliable colonization with most (but not all) strains of the ASF. Subsequently, a novel, simpler porcine microbiota was developed. The novel microbiota reliably colonized the length of the intestinal tract when administered to gnotobiotic piglets. No health problems were observed, and the novel microbiota induced a systemic increase in serum immunoglobulins, in particular IgA and IgM. The Bristol microbiota will be of value for highly controlled, reproducible experiments of the consequences of early microbial colonization on susceptibility to disease in neonatal piglets, and as a biomedical model for the impact of microbial colonization on development of the intestinal mucosa and immune system in neonates.