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Ahmed Abdel-Megeed Mourad A. M. Aboul-Soud Rudolf Mueller Fredua Agyeman Rudolf Salem S. Al-Deyab 《Journal of Polymers and the Environment》2010,18(4):617-625
A gram-negative psychrophilic bacterium, with potential for biodegradation of long-chain n-alkanes was isolated from ice samples collected in Spitzbergen, Denmark. On the basis of results of biochemical and morphological
tests and sequence analysis of 16S rRNA, the strain was identified as Pseudomonas
frederiksbergensis. In this work, a short-chain NAD+-dependent alcohol dehydrogenase (alcDH) (Accession number: AAR13804) from the P.
frederiksbergensis was cloned and transformed in E. coli BL21 (3DE) competent cells. The alcDH activity was highest in the crude extract of cells induced with 1.0 mM IPTG. The recombinant
alcDH enzyme was purified to 93.4% homogeneity using three consecutive purification steps including ammonium sulphate, Q-Sepharose
Fast Flow column and gel filtration chromatography employing Superdex 200 10/30 HR column. Enzyme enrichment and yield levels
of 31.4 folds and 25.5%, respectively, were achieved. While the subunit molecular mass of the enzyme was determined on SDS-PAGE
to be ~38 kDa, the aggregated native form of the enzyme had a molecular mass of ~238 kDa by gel filtration analysis. Reaction
conditions optima for the recombinant alcDH were determined with propan-1-ol as the substrate. While the optimum pH was 9,
the optimum temperature was 35 °C. The alcDH enzyme exhibited moderate thermal stability with half-lives of 150 min at 55 °C,
27 min at 65 °C and 8 min at 75 °C. Results for kinetic parameters indicated that the apparent K
m value for alcDH with propan-1-ol as the substrate was found to be 1.42 mM and the V
max value was 0.63 mmol mg−1 min−1. Experimental evidence revealed that the recombinant alcDH exhibited a wide range of substrate specificity, with higher levels
of specific activity for aliphatic alcohols as compared to secondary alcohols. Taken together, the present study highlights
the potential of alcDH as a member of cold-adapted enzymes in several key biotechnological applications including environmental
bioremediation and biotransformations. It is envisaged that, with the ongoing screening of microorganisms and metagenomes,
directed evolution approaches and the subsequent overexpression of recombinant proteins, more enzymes will be found that are
suitable for bioremediation purposes. 相似文献
318.
Aishwarya Arjunan Holly Bellerose Raul Torres Rotem Ben-Shachar Jodi D. Hoffman Brad Angle Robert Nathan Slotnick Brittany N. Simpson Andrea M. Lewis Pilar L. Magoulas Kelly Bontempo Jeanine Schulze Jennifer Tarpinian Jessica A. Bucher Richard Dineen Allison Goetsch Gabriel A. Lazarin Katherine Johansen Taber 《黑龙江环境通报》2020,40(10):1246-1257
Background
Disease severity is important when considering genes for inclusion on reproductive expanded carrier screening (ECS) panels. We applied a validated and previously published algorithm that classifies diseases into four severity categories (mild, moderate, severe, and profound) to 176 genes screened by ECS. Disease traits defining severity categories in the algorithm were then mapped to four severity-related ECS panel design criteria cited by the American College of Obstetricians and Gynecologists (ACOG).Methods
Eight genetic counselors (GCs) and four medical geneticists (MDs) applied the severity algorithm to subsets of 176 genes. MDs and GCs then determined by group consensus how each of these disease traits mapped to ACOG severity criteria, enabling determination of the number of ACOG severity criteria met by each gene.Results
Upon consensus GC and MD application of the severity algorithm, 68 (39%) genes were classified as profound, 71 (40%) as severe, 36 (20%) as moderate, and one (1%) as mild. After mapping of disease traits to ACOG severity criteria, 170 out of 176 genes (96.6%) were found to meet at least one of the four criteria, 129 genes (73.3%) met at least two, 73 genes (41.5%) met at least three, and 17 genes (9.7%) met all four.Conclusion
This study classified the severity of a large set of Mendelian genes by collaborative clinical expert application of a trait-based algorithm. Further, it operationalized difficult to interpret ACOG severity criteria via mapping of disease traits, thereby promoting consistency of ACOG criteria interpretation.319.
Ronald G Cummings William D Schulze Arthur F Mehr 《Journal of Environmental Economics and Management》1978,5(3):252-267
The primary concern of this paper is the use of wage-infrastructure trade-offs as a measure for the social benefits of municipal infrastructure in boomtowns. A regression based on pooled cross sectional and time series data for 26 towns in the Rocky Moutain region suggests that individuals will “trade off” a 1% increase in per capita stocks of municipal infrastructure for a 0.035% decline in wages. These results are then used to calculate “optimal” levels of infrastructure investment for an example boomtown. 相似文献
320.
Impact of cannibalism on predator-prey dynamics: size-structured interactions and apparent mutualism
Direct and indirect interactions between two prey species can strongly alter the dynamics of predator-prey systems. Most predators are cannibalistic, and as a consequence, even systems with only one predator and one prey include two prey types: conspecifics and heterospecifics. The effects of the complex direct and indirect interactions that emerge in such cannibalistic systems are still poorly understood. This study examined how the indirect interaction between conspecific and heterospecific prey affects cannibalism and predation rates and how the direct interactions between both species indirectly alter the effect of the cannibalistic predator. I tested for these effects using larvae of the stream salamanders Eurycea cirrigera (prey) and Pseudotriton ruber (cannibalistic predator) by manipulating the relative densities of the conspecific and heterospecific prey in the presence and absence of the predator in experimental streams. The rates of cannibalism and heterospecific predation were proportional to the respective densities and negatively correlated, indicating a positive indirect interaction between conspecific and heterospecific prey, similar to "apparent mutualism." Direct interactions between prey species did not alter the effect of the predator. Although both types of prey showed a similar 30% reduction in night activity and switch in microhabitat use in response to the presence of the predator, cannibalism rates were three times higher than heterospecific predation rates irrespective of the relative densities of the two types of prey. Cumulative predation risks differed even more due to the 48% lower growth rate of conspecific prey. Detailed laboratory experiments suggest that the 3:1 difference in cannibalism and predation rate was due to the higher efficiency of heterospecific prey in escaping immediate attacks. However, no difference was observed when the predator was a closely related salamander species, Gyrinophilus porphyriticus, indicating that this difference is species specific. This demonstrates that cannibalism can result in the coupling of predator and prey mortality rates that strongly determines the dynamics of predator-prey systems. 相似文献