Degradation of 1,3-dichloropropene by Pseudomonas cichorii 170

The gram-negative bacterium Pseudomonas cichorii 170, isolated from soil that was repeatedly treated with the nematocide 1,3-dichloropropene, could utilize low concentrations of 1,3-dichloropropene as a sole carbon and energy source, Strain 170 was also able to grow on 3-chloroallyl alcohol, 3-chloroacrylic acid, and several 1-halo-n-alkanes. This organism produced at least three different dehalogenases: a hydrolytic haloalkane dehalogenase specific for haloalkanes and two 3-chloroacrylic acid dehalogenases, one specific for cis-3-chloroacrylic acid and the other specific for trans-3-chloroacrylic acid. The haloalkane dehalogenase and the trans-3-chloroacrylic acid dehalogenase were expressed constitutively, whereas the cis-3-chloroacrylic acid dehalogenase was inducible, The presence of these enzymes indicates that 1,3-dichloropropene is hydrolyzed to 3-chloroallyl alcohol, which is oxidized in two steps to 3-chloroacrylic acid. The latter compound is then dehalogenated, probably forming malonic acid semialdehyde. The haloalkane dehalogenase gene, which is involved in the conversion of 1,3-dichloropropene to 3-chloroallyl alcohol, was cloned and sequenced, and this gene turned out to be identical to the previously studied dhaA gene of the gram-positive bacterium Rhodococcus rhodochrous NCIMB13063, Mutants resistant to the suicide substrate 1,2-dibromoethane lacked haloalkane dehalogenase activity and therefore could not utilize haloalkanes for growth. PCR analysis showed that these mutants had lost at least part of the dhaA gene.

Degradation of carbon disulphide (CS2) in soils and groundwater from a CS2 -contaminated site

This study is the first investigation of biodegradation of carbon disulphide (CS₂) in soil that provides estimates of degradation rates and identifies intermediate degradation products and carbon isotope signatures of degradation. Microcosm studies were undertaken under anaerobic conditions using soil and groundwater recovered from CS₂-contaminated sites. Proposed degradation mechanisms were validated using equilibrium speciation modelling of concentrations and carbon isotope ratios. A first-order degradation rate constant of 1.25 × 10-2 h-1 was obtained for biological degradation with soil. Carbonyl sulphide (COS) and hydrogen sulphide (H₂S) were found to be intermediates of degradation, but did not accumulate in vials. A 13C/12C enrichment factor of -7.5 ± 0.8 ‰ was obtained for degradation within microcosms with both soil and groundwater whereas a 13C/12C enrichment factor of -23.0 ± 2.1 ‰ was obtained for degradation with site groundwater alone. It can be concluded that biological degradation of both CS2-contaminated soil and groundwater is likely to occur in the field suggesting that natural attenuation may be an appropriate remedial tool at some sites. The presence of biodegradation by-products including COS and H₂S indicates that biodegradation of CS₂ is occurring and stable carbon isotopes are a promising tool to quantify CS₂ degradation.

Degradation of 4-fluorobiphenyl by mycorrhizal fungi as determined by (19)F nuclear magnetic resonance spectroscopy and (14)C radiolabelling analysis

The pathways of biotransformation of 4-fluorobiphenyl (4FBP) by the ectomycorrhizal fungus Tylospora fibrilosa and several other mycorrhizal fungi were investigated by using (19)F nuclear magnetic resonance (NMR) spectroscopy in combination with (14)C radioisotope-detected high-performance liquid chromatography ((14)C-HPLC). Under the conditions used in this study T. fibrillosa and some other species degraded 4FBP. (14)C-HPLC profiles indicated that there were four major biotransformation products, whereas (19)F NMR showed that there were six major fluorine-containing products. We confirmed that 4-fluorobiphen-4'-ol and 4-fluorobiphen-3'-ol were two of the major products formed, but no other products were conclusively identified. There was no evidence for the expected biotransformation pathway (namely, meta cleavage of the less halogenated ring), as none of the expected products of this route were found. To the best of our knowledge, this is the first report describing intermediates formed during mycorrhizal degradation of halogenated biphenyls.

Degradation of 4-fluorobiphenyl in soil investigated by 19F NMR spectroscopy and 14C radiolabelling analysis

The incubation of the model pollutant [U-14C]'-4-fluorobiphenyl (4FBP) in soil, in the presence and absence of biphenyl (a co-substrate), was carried out in order to study the qualitative disposition and fate of the compound using 14C-HPLC and 19F NMR spectroscopy. Components accounted for using the radiolabel were volatilization, CO2 evolution, organic solvent extractable and bound residue. Quantitative analysis of these data gave a complete mass balance. After sample preparation. 14C-HPLC was used to establish the number of 4FBP related components present in the organic solvent extract. 19F NMR was also used to quantify the organic extracts and to identify the components of the extract. Both approaches showed that the composition of the solvent extractable fractions comprised only parent compound with no metabolites present. As the 14C radiolabel was found to be incorporated into the soil organic matter this indicates that metabolites were being generated, but were highly transitory as incorporation into the SOM was rapid. The inclusion of the co-substrate biphenyl was to increase the overall rate of degradation of 4FBP in soil. The kinetics of disappearance of parent from the soil using the data obtained were investigated from both techniques. This is the first report describing the degradation of a fluorinated biphenyl in soil.

Growth, dye degradation and ligninolytic activity studies on Zimbabwean white rot fungi

White rot fungi were collected from Chirinda and Chimanimani hardwood forests in Zimbabwe and studied with respect to growth temperature optima and dye decolorization. Temperature optima were found to vary (between 25-37 degreesC) amongst the isolates. The isolates were screened for their ability to degrade the polymeric dyes; blue dextran and Poly R478 and the triphenylmethane dyes; cresol red, crystal violet and bromophenol blue. Semi-quantitative determination of the hydrolytic enzyme activities possessed by the white rot fungi was determined using the API ZYM system. Lignin peroxidase (LiP), manganese peroxidase (MnP) and laccase activities in the fungi were also determined. No LiP was detected in any of the isolates but all isolates showed manganese peroxidase and laccase activities. Time related decolorization studies and optimum pH determinations for Poly R478 degradation by the isolates were carried out in liquid cultures. The most significant rates of Poly R478 decolorization in liquid cultures were found with the following isolates: Trametes cingulata, Trametes versicolor, Trametes pocas, DSPM95 (a species to be identified), Datronia concentrica and Pyenoporus sanguineus. (C) 2001 Elsevier Science Inc. All rights reserved.

Protected area networks and savannah bird biodiversity in the face of climate change and land degradation

The extent to which climate change might diminish the efficacy of protected areas is one of the most pressing conservation questions. Many projections suggest that climate-driven species distribution shifts will leave protected areas impoverished and species inadequately protected while other evidence suggests that intact ecosystems within protected areas will be resilient to change. Here, we tackle this problem empirically. We show how recent changes in distribution of 139 Tanzanian savannah bird species are linked to climate change, protected area status and land degradation. We provide the first evidence of climate-driven range shifts for an African bird community. Our results suggest that the continued maintenance of existing protected areas is an appropriate conservation response to the challenge of climate and environmental change.

CP retrodirective antenna array performance degradation at large elevation angles

At large elevation angles away from boresight the performance of planar phased antenna arrays for circularly polarized, CP, signals suffers from significant gain reduction, worsening of the circular polarization purity, increased pointing error and unwanted dominantly specular lobe radiation. The mechanisms governing this performance deterioration and suggestions for possible rectification are for the first time elaborated in this paper. The points raised in this paper are important when CP retrodirective arrays are to be deployed in self-tracking satellite and terrestrial communication systems mounted on mobile platforms.

Activation of protease calpain by oxidized and glycated LDL increases the degradation of endothelial nitric oxide synthase

Oxidation and glycation of low-density lipoprotein (LDL) promote vascular injury in diabetes; however, the mechanisms underlying this effect remain poorly defined. The present study was conducted to determine the effects of 'heavily oxidized' glycated LDL (HOG-LDL) on endothelial nitric oxide synthase (eNOS) function. Exposure of bovine aortic endothelial cells with HOG-LDL reduced eNOS protein levels in a concentration- and time-dependent manner, without altering eNOS mRNA levels. Reduced eNOS protein levels were accompanied by an increase in intracellular Ca(2+), augmented production of reactive oxygen species (ROS) and induction of Ca(2+)-dependent calpain activity. Neither eNOS reduction nor any of these other effects were observed in cells exposed to native LDL. Reduction of intracellular Ca(2+) levels abolished eNOS reduction by HOG-LDL, as did pharmacological or genetic through calcium channel blockers or calcium chelator BAPTA or inhibition of NAD(P)H oxidase (with apocynin) or inhibition of calpain (calpain 1-specific siRNA). Consistent with these results, HOG-LDL impaired acetylcholine-induced endothelium-dependent vasorelaxation of isolated mouse aortas, and pharmacological inhibition of calpain prevented this effect. HOG-LDL may impair endothelial function by inducing calpain-mediated eNOS degradation in a ROS- and Ca(2+)-dependent manner.

Degradable Polymer Networks and Star Polymers Based on Mixtures of Two Cleavable Dimethacrylate Crosslinkers: Synthesis, Characterization, and Degradation

Mixtures of two cleavable dimethacrylate crosslinkers, the hydrolyzable di(methacryloyloxy-1-ethoxy)methane (DMOEM) and the thermolyzable 1,1-ethylene-diol dimethacrylate (EDDMA), were used for the preparation of neat crosslinker polymer networks, randomly crosslinked polymer networks of methyl methacrylate (MMA), and star polymers of MMA, using group transfer polymerization in tetrahydrofuran (THF). All star polymers and randomly crosslinked polymer networks containing mixtures of the hydrolyzable DMOEM and the thermolyzable EDDMA crosslinkers gave THF-soluble final products when subjected to sequential thermolysis and hydrolysis, in this order. When applying sequential hydrolysis and thermolysis, only the star polymers with an EDDMA crosslinker content equal to or higher than 50% gave THF-soluble final products.

Squirrelpox Virus: Assessing Prevalence, Transmission and Environmental Degradation

Red squirrels (Sciurus vulgaris) declined in Great Britain and Ireland during the last century, due to habitat loss and the introduction of grey squirrels (Sciurus carolinensis), which competitively exclude the red squirrel and act as a reservoir for squirrelpox virus (SQPV). The disease is generally fatal to red squirrels and their ecological replacement by grey squirrels is up to 25 times faster where the virus is present. We aimed to determine: (1) the seropositivity and prevalence of SQPV DNA in the invasive and native species at a regional scale; (2) possible SQPV transmission routes; and, (3) virus degradation rates under differing environmental conditions. Grey (n = 208) and red (n = 40) squirrel blood and tissues were sampled. Enzyme-linked immunosorbent assay (ELISA) and quantitative real-time polymerase chain reaction (qPCR) techniques established seropositivity and viral DNA presence, respectively. Overall 8% of squirrels sampled (both species combined) had evidence of SQPV DNA in their tissues and 22% were in possession of antibodies. SQPV prevalence in sampled red squirrels was 2.5%. Viral loads were typically low in grey squirrels by comparison to red squirrels. There was a trend for a greater number of positive samples in spring and summer than in winter. Possible transmission routes were identified through the presence of viral DNA in faeces (red squirrels only), urine and ectoparasites (both species). Virus degradation analyses suggested that, after 30 days of exposure to six combinations of environments, there were more intact virus particles in scabs kept in warm (25°C) and dry conditions than in cooler (5 and 15°C) or wet conditions. We conclude that SQPV is present at low prevalence in invasive grey squirrel populations with a lower prevalence in native red squirrels. Virus transmission could occur through urine especially during warm dry summer conditions but, more notably, via ectoparasites, which are shared by both species.