Biomedical subjects

W A Dick

Publications and source records attributed to W A Dick.

5 recordsLinked to original sources

PubMed2007

Influence of soil pH and application rate on the oxidation of calcium sulfite derived from flue gas desulfurization.

Calcium sulfite hemihydrate (CaSO(3).0.5H2O), a common byproduct of coal-fired utilities, is fairly insoluble and can decompose to release toxic SO2 under highly acidic soil conditions; however, it can also oxidize to form gypsum. The objective of this study was to examine the effects of application rate and soil pH on the oxidation of calcium sulfite under laboratory conditions. Oxidation rates measured by release of SO4-S to solution decreased with increasing application rate. Leachate SO4-S from soils amended with 1.0 to 3.0 g kg-1 CaSO3 increased over a 21 to 28 d period before reaching a plateau. At 4 g kg-1, maximum SO4-S release was delayed until Week 7. Oxidation and release of SO4-S from soil amended with 3.0 g kg-1 calcium sulfite increased markedly with decreasing soil pH. After only 3 d incubation, the concentrations of SO4-S in aqueous leachates were 77, 122, 170, 220, and 229 mg L-1 for initial soil pH values of 7.8, 6.5, 5.5, 5.1, and 4.0, respectively. At an initial soil pH value of 4.0, oxidation/dissolution did not increase much after 3 d. At higher pH values, oxidation was maximized after 21 d. These results suggest that autumn surface applications of calcium sulfite in no-till systems should permit ample time for oxidation/dissolution reactions to occur without introducing biocidal effects related to oxygen scavenging. Soil and annual crops can thus benefit from additions of soluble Ca and SO4 if calcium sulfite is applied in advance of spring planting.

Calcium↗

PubMed2001

Flue gas desulfurization by-products additions to acid soil: alfalfa productivity and environmental quality.

Flue gas desulfurization (FGD) by-products are created when coal is burned and SO2 is removed from the flue gases. These FGD by-products are often alkaline and contain many plant nutrients. Land application of FGD by-products is encouraged but little information is available related to plant responses and environmental impacts concerning such use. Agricultural lime (ag-lime) and several new types of FGD by-products which contain either vermiculite or perlite were applied at 0, 0.5, 1.0, and 2.0 times the soil's lime requirement (LR) rate to an acidic soil (Wooster silt loam). The highest FGD by-products application rate was equivalent to 75.2 Mg ha(-1). Growth of alfalfa (Medicago sativa L.) was significantly increased compared to the untreated control in the second year after treatment with yields for the 1 x LR rate of FGD approximately 7-8 times greater compared to the untreated control and 30% greater than for the commercial ag-lime. Concentrations of Mo in alfalfa were significantly increased by FGD by-products application, compared to the untreated control, while compared to the ag-lime treatment, concentrations of B increased and Ba decreased. No soil contamination problems were observed, even at the 2xLR rate, indicating these materials can be safely applied to agricultural soils.

Agriculture↗

PubMed1995

An improved Escherichia coli-Rhodococcus shuttle vector and plasmid transformation in Rhodococcus spp. using electroporation.

The genetic studies of metabolically diverse Rhodococcus spp. have been hampered by the lack of a system of introducing exogenous DNA. The authors improved an existing Escherichia coli-Rhodococcus shuttle vector (pMVS301) by removing much of the DNA not needed for replication and adding a multicloning site. This improved vector (pBS305) is 7.9 kb in length. Its ability to transform Rhodococcus was tested using electroporation parameters optimized for introduction of pMVS301 into Rhodococcus. Transformation efficiencies as high as 10(5) cfu micrograms-1 DNA were obtained although efficiencies varied depending on the Rhodococcus strain tested. The improved vector pBS305 offers great utility for genetic studies of Rhodococcus because its small size enables movement of large inserts of DNA into Rhodococcus, it has multicloning sites, contains a highly selective thiostrepton marker, and can be replicated in both E. coli and Rhodococcus.

DNA, Bacterial↗

PubMed1993

Spheroplast formation and plasmid isolation from Rhodococcus spp.

The genus Rhodococcus comprises aerobic gram-positive actinomycetes that show considerable morphological and metabolic diversity and are known to be involved in the development of plant diseases and degradation of environmental pollutants. We describe a method for cell lysis and large plasmid DNA isolation from Rhodococcus by creating lysozyme susceptible cells by predigestion with the enzyme mutanolysin. Mutanolysin action resulted in the liberation of reducing sugars and free amino acids from the peptidoglycan layers of the cell wall. A 1-h predigestion with mutanolysin followed by a 0.5-h incubation with lysozyme resulted in spheroplast formation. Complete lysis of cells and efficient isolation of intact large plasmid DNA (108 kb) from wild-type Rhodococcus strains was confirmed.

Chromatography, High Pressure Liquid↗

PubMed1991

Mechanisms of h(2)s production from cysteine and cystine by microorganisms isolated from soil by selective enrichment.

Hydrogen sulfide (H(2)S) is a major component of biogenic gaseous sulfur emissions from terrestrial environments. However, little is known concerning the pathways for H(2)S production from the likely substrates, cysteine and cystine. A mixed microbial culture obtained from cystine-enriched soils was used in assays (50 min, 37 degrees C) with 0.05 M Tris-HCl (pH 8.5), 25 mumol of l-cysteine, 25 mumol of l-cystine, and 0.04 mumol of pyridoxal 5'-phosphate. Sulfide was trapped in a center well containing zinc acetate, while pyruvate was measured by derivatization with 2,4-dinitrophenylhydrazine. Sulfide and total pyruvate production were 17.6 and 17.2 nmol mg of protein min, respectively. Dithiothreitol did not alter reaction stoichiometry or the amount of H(2)S and total pyruvate, whereas N-ethylmaleimide reduced both H(2)S and total pyruvate production equally. The amount of H(2)S produced was reduced by 96% when only l-cystine was included as the substrate in the assay and by 15% with the addition of propargylglycine, a specific suicide inhibitor of cystathionine gamma-lyase. These data indicate that the substrate for the reaction was cysteine and the enzyme responsible for H(2)S and pyruvate production was cysteine desulfhydrase (EC 4.4.1.1). The enzyme had a K(m) of 1.32 mM and was inactivated by temperatures greater than 60 degrees C. Because cysteine is present in soil and cysteine desulfhydrase is an inducible enzyme, the potential for H(2)S production by this mechanism exists in terrestrial environments. The relative importance of this mechanism compared with other processes involved in H(2)S production from soil is unknown.

Journal Article↗