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Groenhagen U.,TU Braunschweig | Baumgartner R.,University of Zurich | Bailly A.,University of Zurich | Gardiner A.,University of Zurich | And 4 more authors.
Journal of Chemical Ecology | Year: 2013

Increasing evidence indicates that volatile compounds emitted by bacteria can influence the growth of other organisms. In this study, the volatiles produced by three different strains of Burkholderia ambifaria were analysed and their effects on the growth of plants and fungi, as well as on the antibiotic resistance of target bacteria, were assessed. Burkholderia ambifaria emitted highly bioactive volatiles independently of the strain origin (clinical environment, rhizosphere of pea, roots of maize). These volatile blends induced significant biomass increase in the model plant Arabidopsis thaliana as well as growth inhibition of two phytopathogenic fungi (Rhizoctonia solani and Alternaria alternata). In Escherichia coli exposed to the volatiles of B. ambifaria, resistance to the aminoglycoside antibiotics gentamicin and kanamycin was found to be increased. The volatile blends of the three strains were similar, and dimethyl disulfide was the most abundant compound. Sulfur compounds, ketones, and aromatic compounds were major groups in all three volatile profiles. When applied as pure substance, dimethyl disulfide led to increased plant biomass, as did acetophenone and 3-hexanone. Significant fungal growth reduction was observed with high concentrations of dimethyl di- and trisulfide, 4-octanone, S-methyl methanethiosulphonate, 1-phenylpropan-1-one, and 2-undecanone, while dimethyl trisulfide, 1-methylthio-3-pentanone, and o-aminoacetophenone increased resistance of E. coli to aminoglycosides. Comparison of the volatile profile produced by an engineered mutant impaired in quorum-sensing (QS) signalling with the corresponding wild-type led to the conclusion that QS is not involved in the regulation of volatile production in B. ambifaria LMG strain 19182. © 2013 Springer Science+Business Media New York. Source

Niu S.,University of Oklahoma | Luo Y.,University of Oklahoma | Luo Y.,Fudan University | Fei S.,University of Oklahoma | And 67 more authors.
New Phytologist | Year: 2012

It is well established that individual organisms can acclimate and adapt to temperature to optimize their functioning. However, thermal optimization of ecosystems, as an assemblage of organisms, has not been examined at broad spatial and temporal scales. Here, we compiled data from 169 globally distributed sites of eddy covariance and quantified the temperature response functions of net ecosystem exchange (NEE), an ecosystem-level property, to determine whether NEE shows thermal optimality and to explore the underlying mechanisms. We found that the temperature response of NEE followed a peak curve, with the optimum temperature (corresponding to the maximum magnitude of NEE) being positively correlated with annual mean temperature over years and across sites. Shifts of the optimum temperature of NEE were mostly a result of temperature acclimation of gross primary productivity (upward shift of optimum temperature) rather than changes in the temperature sensitivity of ecosystem respiration. Ecosystem-level thermal optimality is a newly revealed ecosystem property, presumably reflecting associated evolutionary adaptation of organisms within ecosystems, and has the potential to significantly regulate ecosystem-climate change feedbacks. The thermal optimality of NEE has implications for understanding fundamental properties of ecosystems in changing environments and benchmarking global models. © 2012 The Authors. New Phytologist © 2012 New Phytologist Trust. Source

Mann S.,Federal Research Station Agroscope Reckenholz Tanikon | Gennaio M.-P.,Federal Research Station Agroscope Reckenholz Tanikon
Journal of Environmental Planning and Management | Year: 2010

While economic research on environmental policy is mainly concerned with instruments, political science concentrates on actors. The issue of centralization needs to be analysed using a multidisciplinary approach because it is connected with both actors and instruments. Linking the Advocacy Coalition Framework with an economic approach, the paper first develops an innovative model in order to understand the mechanisms of centralisation and decentralisation in the different phases of policy processes. Focusing on environmental policy, the idea is developed that environmental policy needs the push of centralisation in order to institutionalise the prevailing social norm, but then should be organized decentrally to account for regional differences. The examples of air pollution, climate change and urban sprawl are used to test the explanatory power of the theoretical approach. © 2010 University of Newcastle upon Tyne. Source

Yi C.,Queens College, City University of New York | Li R.,Oak Ridge National Laboratory | Wolbeck J.,Pennsylvania State University | Xu X.,Queens College, City University of New York | And 146 more authors.
Environmental Research Letters | Year: 2010

Understanding the relationships between climate and carbon exchange by terrestrial ecosystems is critical to predict future levels of atmospheric carbon dioxide because of the potential accelerating effects of positive climate-carbon cycle feedbacks. However, directly observed relationships between climate and terrestrial CO2exchange with the atmosphere across biomes and continents are lacking. Here we present data describing the relationships between net ecosystem exchange of carbon (NEE) and climate factors as measured using the eddy covariance method at 125 unique sites in various ecosystems over six continents with a total of 559 site-years. We find that NEE observed at eddy covariance sites is (1) a strong function of mean annual temperature at mid- and high-latitudes, (2) a strong function of dryness at mid- and low-latitudes, and (3) a function of both temperature and dryness around the mid-latitudinal belt (45°N). The sensitivity of NEE to mean annual temperature breaks down at ∼16 ®C (a threshold value of mean annual temperature), above which no further increase of CO,.2uptake with temperature was observed and dryness influence overrules temperature influence. © 2010 lOP Publishing Ltd. Source

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