Knockout of the high-coupling cytochrome aa3 oxidase reduces TCA cycle fluxes in Bacillus subtilis

The metabolic impact of electron rerouting in the respiratory chain of Bacillus subtilis was quantitatively assessed during batch growth of quinol oxidase mutants by 13C-tracer experiments. While disruption of the low-coupling cytochrome bd oxidase was without any apparent phenotype, deletion of the high-coupling cytochrome aa3 oxidase caused a severe reduction of tricarboxylic acid cycle fluxes and increased overflow metabolism. Since the product-corrected biomass yields were identical in mutants and parent, the results show that efficient ATP generation is not overly important for exponential growth of B. subtilis in batch cultur

Functional expression of arginine kinase improves recovery from pH stress of Escherichia coli

Acid stress in Escherichia coli involves a complex resource- and energy-consuming response mechanism. By overexpression of arginine kinase from Limulus polyphemus in E.coli, we improved the recovery from a transient pH stress. While wild type E.coli resumed growth after a transient pH reduction to pH3 for 1h with a rate that was 25% lower than before the stress, the arginine kinase expressing strain continued to grow as rapidly as before. This effect is presumably caused by the physiological function of arginine kinase as a short term energy buffer in the form of phosphoarginine, but a pH-buffering effect cannot be exclude

Численное решение задачи о распространении загрязнения в водной среде

Реки являются основным источником водоснабжения. В настоящее время еще недостаточно эффективны способы очистки воды, особенно в случаях аварийных залповых выбросов различных веществ. Поэтому представляют интерес методы оценки состояния водной среды, с помощью которых осуществляется описание распространения загрязняющих примесей в водоемах. В данной работе представлена математическая модель процесса тепло- и массопереноса, расчета полей скорости, температуры и концентраций загрязняющих компонент в водоеме. Разработанные методы предсказания уровней распределения загрязняющих примесей, попадающих в водную среду, могут быть использованы для контроля качества речной воды, в том числе при условии аварийных выбросов различных веществ в водоем

The PEP—pyruvate—oxaloacetate node as the switch point for carbon flux distribution in bacteria: We dedicate this paper to Rudolf K. Thauer, Director of the Max-Planck-Institute for Terrestrial Microbiology in Marburg, Germany, on the occasion of his 65th birthday

In many organisms, metabolite interconversion at the phosphoenolpyruvate (PEP)-pyruvate-oxaloacetate node involves a structurally entangled set of reactions that interconnects the major pathways of carbon metabolism and thus, is responsible for the distribution of the carbon flux among catabolism, anabolism and energy supply of the cell. While sugar catabolism proceeds mainly via oxidative or non-oxidative decarboxylation of pyruvate to acetyl-CoA, anaplerosis and the initial steps of gluconeogenesis are accomplished by C3- (PEP- and/or pyruvate-) carboxylation and C4- (oxaloacetate- and/or malate-) decarboxylation, respectively. In contrast to the relatively uniform central metabolic pathways in bacteria, the set of enzymes at the PEP-pyruvate-oxaloacetate node represents a surprising diversity of reactions. Variable combinations are used in different bacteria and the question of the significance of all these reactions for growth and for biotechnological fermentation processes arises. This review summarizes what is known about the enzymes and the metabolic fluxes at the PEP-pyruvate-oxaloacetate node in bacteria, with a particular focus on the C3-carboxylation and C4-decarboxylation reactions in Escherichia coli, Bacillus subtilis and Corynebacterium glutamicum. We discuss the activities of the enzymes, their regulation and their specific contribution to growth under a given condition or to biotechnological metabolite production. The present knowledge unequivocally reveals the PEP-pyruvate-oxaloacetate nodes of bacteria to be a fascinating target of metabolic engineering in order to achieve optimized metabolite productio

Optimization of PV Battery Systems Using Genetic Algorithms

AbstractA modular simulation model of a PV battery system has been developed and integrated into a genetic algorithm framework in order to evaluate optimal sizing of such systems under various boundary conditions. The presented paper describes the simulation assumptions and presents optimization results for a PV battery system having a DC topology, comparing current economic scenarios with and without KfW funding. Sensitivity analyses provide information on critical boundaries to reach economic operation. The fitness of a system is evaluated based on the levelized cost of electricity (LCOE) defining the average cost – including all investment and operation cost over the system lifetime – per kWh supplied to the load