@article{VorburgerNedielkovBrosigetal.2016, author = {Vorburger, Thomas and Nedielkov, Ruslan and Brosig, Alexander and Bok, Eva and Schunke, Emina and Steffen, Wojtek and Mayer, Sonja and Goetz, Friedrich and M{\"o}ller, Heiko Michael and Steuber, Julia}, title = {Role of the Na+-translocating NADH:quinone oxidoreductase in voltage generation and Na+ extrusion in Vibrio cholerae}, series = {Biochimica et biophysica acta : Bioenergetics}, volume = {1857}, journal = {Biochimica et biophysica acta : Bioenergetics}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0005-2728}, doi = {10.1016/j.bbabio.2015.12.010}, pages = {473 -- 482}, year = {2016}, abstract = {For Vibrio cholerae, the coordinated import and export of Na+ is crucial for adaptation to habitats with different osmolarities. We investigated the Na+-extruding branch of the sodium cycle in this human pathogen by in vivo Na-23-NMR spectroscopy. The Na+ extrusion activity of cells was monitored after adding glucose which stimulated respiration via the Na+-translocating NADH:quinone oxidoreductase (Na+-NQR). In a V. cholerae deletion mutant devoid of the Na+-NQR encoding genes (nqrA-F), rates of respiratory Na+ extrusion were decreased by a factor of four, but the cytoplasmic Na+ concentration was essentially unchanged. Furthermore, the mutant was impaired in formation of transmembrane voltage (Delta psi, inside negative) and did not grow under hypoosmotic conditions at pH 8.2 or above. This growth defect could be complemented by transformation with the plasmid encoded nqr operon. In an alkaline environment, Na+/H+ antiporters acidify the cytoplasm at the expense of the transmembrane voltage. It is proposed that, at alkaline pH and limiting Na+ concentrations, the Na+-NQR is crucial for generation of a transmembrane voltage to drive the import of H+ by electrogenic Na+/H+ antiporters. Our study provides the basis to understand the role of the Na+-NQR in pathogenicity of V. cholerae and other pathogens relying on this primary Na+ pump for respiration. (C) 2015 Elsevier B.V. All rights reserved.}, language = {en} } @article{AttermeyerGrossartFluryetal.2017, author = {Attermeyer, Katrin and Grossart, Hans-Peter and Flury, Sabine and Premke, Katrin}, title = {Bacterial processes and biogeochemical changes in the water body of kettle holes - mainly driven by autochthonous organic matter?}, series = {Aquatic sciences : research across boundaries}, volume = {79}, journal = {Aquatic sciences : research across boundaries}, publisher = {Springer}, address = {Basel}, issn = {1015-1621}, doi = {10.1007/s00027-017-0528-1}, pages = {675 -- 687}, year = {2017}, abstract = {Kettle holes are small inland waters formed from glacially-created depressions often situated in agricultural landscapes. Due to their high perimeter-to-area ratio facilitating a high aquatic-terrestrial coupling, kettle holes can accumulate high concentrations of organic carbon and nutrients, fueling microbial activities and turnover rates. Thus, they represent hotspots of carbon turnover in the landscape, but their bacterial activities and controlling factors have not been well investigated. Therefore, we aimed to assess the relative importance of various environmental factors on bacterial and biogeochemical processes in the water column of kettle holes and to disentangle their variations. In the water body of ten kettle holes in north-eastern Germany, we measured several physico-chemical and biological parameters such as carbon quantity and quality, as well as bacterial protein production (BP) and community respiration (CR) in spring, early summer and autumn 2014. Particulate organic matter served as an indicator of autochthonous production and represented an important parameter to explain variations in BP and CR. This notion is supported by qualitative absorbance indices of dissolved molecules in water samples and C: N ratios of the sediments, which demonstrate high fractions of autochthonous organic matter (OM) in the studied kettle holes. In contrast, dissolved chemical parameters were less important for bacterial activities although they revealed strong differences throughout the growing season. Pelagic bacterial activities and dynamics might thus be regulated by autochthonous OM in kettle holes implying a control of important biogeochemical processes by internal primary production rather than facilitated exchange with the terrestrial surrounding due to a high perimeter-to-area ratio.}, language = {en} } @article{EinumFossenParryetal.2019, author = {Einum, Sigurd and Fossen, Erlend I. F. and Parry, Victor and Pelabon, Christophe}, title = {Genetic variation in metabolic rate and correlations with other energy budget components and life history in Daphnia magna}, series = {Evolutionary Biology}, volume = {46}, journal = {Evolutionary Biology}, number = {2}, publisher = {Springer}, address = {New York}, issn = {0071-3260}, doi = {10.1007/s11692-019-09473-x}, pages = {170 -- 178}, year = {2019}, abstract = {Much is known about the genetic variance in certain components of metabolism, most notably resting and maximum metabolic rate. This is in stark contrast to the lack of information on genetic variance in the metabolic rate of individuals that feed and express routine activity, and how this rate correlates with other components of the energy budget or life history traits. Here we quantify genetic variance in metabolic rate (MR) under such conditions, as well as food consumption, juvenile somatic growth rate and age at maturation under ad lib food availability in a set of 10 clones of Daphnia magna from a natural population. Broad sense evolvabilities (0.16 0.56\%) were on the same order of magnitude as those typically observed for physiological and life history traits, and suggest that all these traits have the potential to evolve within this population. We did not find support for the previously hypothesized positive genetic correlation between metabolic rate and growth rate. Rather, the patterns of genetic correlations suggest that genetic variance in food consumption is the single most influential trait shaping somatic growth rate, but that additional variance in growth can be explained by considering the joint effect of consumption and MR. The genetic variance in consumption and MR also translated into genetic variance in age at maturation, creating a direct link between these energy budget components and a life history trait with strong fitness effects. Moreover, a weak positive correlation between MR and food consumption suggests the presence of substantial amounts of independent genetic control of these traits, consistent with results obtained using genomic approaches.}, language = {en} }