Alexander J. B. Zehnder

Bio: Alexander J. B. Zehnder is an academic researcher from Swiss Federal Institute of Aquatic Science and Technology. The author has contributed to research in topics: Polyphosphate & Phosphate. The author has an hindex of 78, co-authored 188 publications receiving 23933 citations. Previous affiliations of Alexander J. B. Zehnder include École Polytechnique Fédérale de Lausanne & ETH Zurich.

Biology of anaerobic microorganisms

Abstract: Geochemistry and Biogeochemistry of Anaerobic Habitats (A. Zehnder & W. Stumm). Microbiology, Physiology, and Ecology of Phototrophic Bacteria (M. Madigan). Molecular Mechanisms of Bacterial Photosynthesis (J. Amesz & D. Knaff). Ecology of Denitrification and Dissimilatory Nitrate Reduction to Ammonium (J. Tiedje). Dissimilatory Reduction of Oxidized Nitrogen Compounds (A. Stouthamer). Microbial Reduction of Manganese and Iron (W. Ghiorse). Anaerobic Microbial Degradation of Cellulose, Lignin, Oligolignols, and Monoaromatic Lignin Derivatives (P. Colberg). Anaerobic Hydrolosis and Fermentation of Fats and Proteins (M. McInerney). Acetogenesis (J. Dolfing). Microbiology and Ecology of Sulfate- and Sulfur-Reducing Bacteria (F. Widdel). Dissimilatory Reduction of Sulfur Compounds (J. LeGall & G. Fauque). Biogeochemistry of Methanogenic Bacteria (R. Oremland). Biochemistry of Methane Production (G. Vogels, et al.). Principles and Limits of Anaerobic Degradation: Environmental and Technological Aspects (B. Schink). Index.

The role of bacterial cell wall hydrophobicity in adhesion.

Abstract: In this study, the adhesion of bacteria differing in surface hydrophobicity was investigated. Cell wall hydrophobicity was measured as the contact angle of water on a bacterial layer collected on a microfilter. The contact angles ranged from 15 to 70 degrees. This method was compared with procedures based upon adhesion to hexadecane and with the partition of cells in a polyethylene glycol-dextran two-phase system. The results obtained with these three methods agreed reasonably well. The adhesion of 16 bacterial strains was measured on sulfated polystyrene as the solid phase. These experiments showed that hydrophobic cells adhered to a greater extent than hydrophilic cells. The extent of adhesion correlated well with the measured contact angles (linear regression coefficient, 0.8).

Electrophoretic mobility and hydrophobicity as a measured to predict the initial steps of bacterial adhesion.

Abstract: The relationship between physiochemical surface parameters and adhesion of bacterial cells to negatively charged polystyrene was studied. Cell surface hydrophobicity and electrokinetic potential were determined by contact angle measurement and electrophoresis, respectively. Both parameters influence cell adhesion. The effect of the electrokinetic potential increases with decreasing hydrophobicity. Cell surface characteristics determining adhesion are influenced by growth conditions. At high growth rates, bacterial cells tend to become more hydrophobic. This fact can be of ecological significance for controlling the spread of bacteria throughout the environment.

REACTIVE OXYGEN SPECIES: Metabolism, Oxidative Stress, and Signal Transduction

Abstract: Several reactive oxygen species (ROS) are continuously produced in plants as byproducts of aerobic metabolism. Depending on the nature of the ROS species, some are highly toxic and rapidly detoxified by various cellular enzymatic and nonenzymatic mechanisms. Whereas plants are surfeited with mechanisms to combat increased ROS levels during abiotic stress conditions, in other circumstances plants appear to purposefully generate ROS as signaling molecules to control various processes including pathogen defense, programmed cell death, and stomatal behavior. This review describes the mechanisms of ROS generation and removal in plants during development and under biotic and abiotic stress conditions. New insights into the complexity and roles that ROS play in plants have come from genetic analyses of ROS detoxifying and signaling mutants. Considering recent ROS-induced genome-wide expression analyses, the possible functions and mechanisms for ROS sensing and signaling in plants are compared with those in animals and yeast.

Solutions for a cultivated planet

Abstract: Increasing population and consumption are placing unprecedented demands on agriculture and natural resources. Today, approximately a billion people are chronically malnourished while our agricultural systems are concurrently degrading land, water, biodiversity and climate on a global scale. To meet the world's future food security and sustainability needs, food production must grow substantially while, at the same time, agriculture's environmental footprint must shrink dramatically. Here we analyse solutions to this dilemma, showing that tremendous progress could be made by halting agricultural expansion, closing 'yield gaps' on underperforming lands, increasing cropping efficiency, shifting diets and reducing waste. Together, these strategies could double food production while greatly reducing the environmental impacts of agriculture.