Network context and selection in the evolution to enzyme specificity

Enzymes are thought to have evolved highly specific catalytic activities from promiscuous ancestral proteins. By analyzing a genome-scale model of Escherichia coli metabolism, we found that 37% of its enzymes act on a variety of substrates and catalyze 65% of the known metabolic reactions. However, it is not apparent why these generalist enzymes remain. Here, we show that there are marked differences between generalist enzymes and specialist enzymes, known to catalyze a single chemical reaction on one particular substrate in vivo. Specialist enzymes (i) are frequently essential, (ii) maintain higher metabolic flux, and (iii) require more regulation of enzyme activity to control metabolic flux in dynamic environments than do generalist enzymes. Furthermore, these properties are conserved in Archaea and Eukarya. Thus, the metabolic network context and environmental conditions influence enzyme evolution toward high specificity.     

Zur Verbreitung und Bedeutung von Pilzkrankheiten in K?rnerfuttererbsen (Pisum sativum L.) in Deutschland

Monitoring of the pathogen spectrum in grain peas (Pisum sativum L.) was conducted in Germany between 2005 and 2007. The outcome of this study implies that the infections of pathogens depend on the annual weather condition and the geographic area.Ascochyta pinodes, which infects aerial plant organs, was the pathogen found most frequently (on average 61, 8%). Especially in years with moist weather conditions a more severe spreading of the pathogen could be observed. Similarly, the occurrence ofBotrytis cinerea depends on the weather conditions. In 2007 were optimal conditions for infections and consequentlyB. cinerea was found with a high frequency of about 70%. Regarding diseases on root and stem base, this study clearly shows that infection of less prominent Fusarium species, such asF. redolens andF. avenaceum was significantly higher compared toF. oxysporum andF. solani.     

Sediment Properties for Assessing the Erosion Risk of Contaminated Riverine Sites. An approach to evaluate sediment properties and their covariance patterns over depth in relation to erosion resistance. First investigations in natural sediments (11 pp)

Background, Aim and Scope   Riverine sediments store large quantities of hazardous contaminants, remaining a 'legacy of the past' world-wide. Natural events such as floods may cause the resuspension of polluted sediments and accordingly, the former immobilized contaminants might become bioavailable and toxic again. Hence, a comprehensive erosion risk assessment of contaminated sites is of crucial importance. The present study aimed to implement 'master-variables' for a reliable, easy-to-manage and economically more viable determination of stability in cohesive sediments. Materials and Methods: A wide range of physico-chemical (bulk density, water content, particle size, mineral composition, cation exchange capacity / CEC, total organic matter / TOC, liquid and plastic limits of a soil) and biological (macrofauna abundances, microalgal biomass and species composition, bacterial cell numbers, EPS fractions such as carbohydrates and proteins) properties were determined simultaneously over depth spanning the zone between 0-35 cm. The data were related to sediment stability, determined as the 'critical shear stress for mass erosion' in the SETEG (Stroemungskanal zur Ermittlung der tiefenabhaengigen Erosionsstabilitaet von Gewaessersedimenten) - flume. The investigations were done on natural sediments, thereby covering vertical (over depth), spatial (different study sites) and temporal (different seasons) aspects to ensure the transferability of the data. Here, first data originating from three contaminated reservoirs in the lock-regulated River Neckar / Germany are presented. Results: Comparison of the rather low critical shear stress values (resisting force of sediment, determined in SETEG) with the possibly occurring natural bottom shear stresses (attacking force, calculated for different hydraulic scenarios) at the three reservoirs indicated a severe risk of sediment erosion even under moderate hydraulic conditions and was not restricted to the surface. Critical shear stress was characterised by the following sediment properties of depth, grain size, CEC (Cation Exchange Capacity) and concentrations of TOC (Total Organic Carbon), proteins as well as carbohydrates (water- and resin-extractable). Firstly, biological stabilisation by extracellular polymeric substances (EPS) could be shown for riverine sediments, even over depth. Secondly, erosion resistance was determined by the inter-particles forces, an interplay of the biologically produced compounds constituting active surfaces and the binding capacity as well as charge densities of the sediments. The combined influence of sedimentological and biological properties on sediment stability over depth was assessed by PCA (Principal Component Analysis). Discussion: Hence, a better correlation coefficient between sediment stability and the master variables could be achieved (Main component II: Polymeric substances, R = 0.7, Main component III: Grain size, TOC, CEC, R = 0.9) compared to single correlations. Conclusions: The present paper revealed the combined influence of physico-chemical and biological properties on sediment stability over depth by simultaneous investigation and statistical evaluation. It can be shown, that inter-particle forces, determined by particles size classes, CEC, TOC and polymeric substances such as proteins and carbohydrates, affected sediment stability most. Thereby, the impact of biogenic sediment mediation on riverine sediment stabilisation became evident, even over depth, where mostly sedimentological parameters were considered as important before. Recommendations and Perspectives: The importance of a comprehensive risk assessment of contaminated riverine sites was again highlighted in the present study by the comparison of natural occurring bottom shear stresses with the determined sediment erosion resistance. If a realistic risk assessment is to be derived, the stabilizing potential of micro-organisms needs to be taken into account and the covariance patterns of biological and physico-chemical sediment properties have to be addressed.     

Evaluation of thermally modified beech and spruce wood and their properties by FT-NIR spectroscopy

Quality assessment of thermally modified spruce (Picea abies (L.) Karst) and beech (Fagus sylvatica L.) wood and of the corresponding reference samples was carried out by means of non-destructive FT-NIR spectroscopic measurements and PLS regression. Oven-dry and basic density as well as MOE and MOR determined by 3-point bending tests were evaluated. The focus was put on specimens produced from material that had been thermally modified in an industrial scale kiln. Modelling results range from poor to very good. The results of the spectra taken from the spruce samples resulted in better prediction results than the spectra of the beech samples. This could be due to different proveniences or variation in the industrial modification process. The results indicate that FT-NIR surface measurements of sound thermally modified wood samples could be applied to evaluate several characteristics before and after the modification process. The method could be used for screening during pre-sorting of thermally modified wood.     

Effect of the estimation of forest management and decay of dead woody material on the reliability of carbon stock and carbon stock changes—A simulation study

The IPCC-GPG on Greenhouse Gas Monitoring offers countries several options for reporting. The current study selected management effects and decay of dead woody material to demonstrate the dependence of different approaches and assumptions for carbon stock and carbon stock change estimates. For a given set of inventory data the reported change of carbon stock varied between 3.1 tonnes C ha⁻¹ yr⁻¹and 34.4 tonnes C ha⁻¹ yr⁻¹ for a 10-year period.Based on the available data set from a test area in the federal state of Salzburg (Austria) the effect of different scenarios for harvesting operations and mortality on reported carbon release was studied. The scenarios covered timber utilization at different points in time and two mortality rates (constant and exponential). A proportion of harvesting was assumed to remain inside the forest as logging residues and entered together with mortality a decay process. Two different lifetimes for decay (10 and 50 years) and constant and negative exponential decay rates were simulated. Those decisions affect the amount of carbon released considerably. For a 10-year period between 5% and 80% of the carbon content of dead woody material that accumulated within the period is released to the atmosphere.     

Effects of temperature, wetness duration and leaf age on incubation and latent periods of black leaf mold (Pseudocercospora fuligena) on fresh market tomatoes

Black leaf mold (BLM), caused by Pseudocercospora fuligena is a serious threat to tomato production in the humid tropics. Accurate information about the incubation (IP) and latent period (LP) under various host susceptibility and weather favourability circumstances will help to formulate holistic approaches to manage this disease. In this study, effects of temperature, wetness duration, and leaf age on the monocyclic components (IP and LP) of BLM were studied from growth chamber (GC) and greenhouse (GH) experiments as well as detached leaf assays in growth cabins. Linear interpolation and inflection point (of logistic regression model) methods were used to determine IP and LP. These two methods were highly correlated in GC (r ²?=?0.89; P?<?0.0001) and GH experiments (r ²?=?0.90; P?<?0.0001) except when the epidemics were not asymptotic. Thus, IP and LP were estimated according to inflection point method. There was a delay of at least 5 days of IP and LP when plants were left in non-humid open environment than when exposed to wetness durations of 1, 2 or 3 days after inoculation. In general, IP and LP became shorter as the temperature increased from 20–24 and then to 28 °C. In growth chambers, there was more disease and consequently shorter IP and LP on young and unfolded tomato leaves that were 1-, 3-, or 5-week old at the time of inoculation than 7-week old leaves. In the greenhouse, there was about 50 % more disease incidence and sporulation on 1-week than 3-week old leaves. The shortest IP (8–11 days) and LP (12–13 days) were recorded from two out of three GH experiments on 1-week old leaves at an ambient mean temperature of 28.5 °C. This study implicated that fresh market tomatoes planted during warm temperatures in 50-mesh greenhouses and exposed to extended periods of wetness are highly prone to BLM infection at their young stages of growth.     

Complement C3 in Bernese Mountain dogs

Background: Previous research suggests that low serum concentrations of the third component of complement (C3) are associated with both the susceptibility to infectious agents such as Borrelia burgdorferi and the development of glomerular disease. We hypothesized that low levels of C3 are associated with the coincident occurrence of B. burgdorferi infection and glomerulonephritis in Bernese Mountain dogs. Objectives: The aims of this study were to evaluate the serum concentration of C3 in Bernese Mountain dogs with and without antibodies against B. burgdorferi and to compare this concentration with that of healthy control dogs. Methods: Eighty‐three clinically healthy Bernese Mountain dogs and 46 control dogs were included. Antibodies against B. burgdorferi were determined using an ELISA with a whole cell sonicate as antigen. Results were confirmed using Western blot. C3 was measured using a single radial immunodiffusion test. Results were reported as the percentage concentration of C3 compared with that in pooled preserved canine serum (100% C3 concentration). Results: Median C3 concentration was 128.5% in Bernese Mountain dogs with antibodies against B. burgdorferi, 133.5% in B. burgdorferi‐negative Bernese Mountain dogs, 87.8% in positive control dogs, and 102.2% in negative control dogs. Within Bernese Mountain and control groups, C3 was lower in dogs with antibodies against B. burgdorferi compared with those without. Percentage concentration of C3 was higher in healthy Bernese Mountain dogs compared with control dogs. Conclusion: Low C3 concentration is not an explanation for the high prevalence of B. burgdorferi infections and glomerular disease in Bernese Mountain dogs.