Energy source

About: Energy source is a research topic. Over the lifetime, 88845 publications have been published within this topic receiving 1953134 citations. The topic is also known as: energy resource & source of energy.

Effect of Global Regulators RpoS and Cyclic-AMP/CRP on the Catabolome and Transcriptome of Escherichia coli K12 during Carbon- and Energy-Limited Growth.

Abstract: For heterotrophic microbes, limited availability of carbon and energy sources is one of the major nutritional factors restricting the rate of growth in most ecosystems. Physiological adaptation to this hunger state requires metabolic versatility which usually involves expression of a wide range of different catabolic pathways and of high-affinity carbon transporters; together, this allows for simultaneous utilization of mixtures of carbonaceous compounds at low concentrations. In Escherichia coli the stationary phase sigma factor RpoS and the signal molecule cAMP are the major players in the regulation of transcription under such conditions; however, their interaction is still not fully understood. Therefore, during growth of E. coli in carbon-limited chemostat culture at different dilution rates, the transcriptomes, expression of periplasmic proteins and catabolomes of strains lacking one of these global regulators, either rpoS or adenylate cyclase (cya), were compared to those of the wild-type strain. The inability to synthesize cAMP exerted a strong negative influence on the expression of alternative carbon source uptake and degradation systems. In contrast, absence of RpoS increased the transcription of genes belonging to high-affinity uptake systems and central metabolism, presumably due to reduced competition of σD with σS. Phenotypical analysis confirmed this observation: The ability to respire alternative carbon substrates and to express periplasmic high-affinity binding proteins was eliminated in cya and crp mutants, while these properties were not affected in the rpoS mutant. As expected, transcription of numerous stress defence genes was negatively affected by the rpoS knock-out mutation. Interestingly, several genes of the RpoS stress response regulon were also down-regulated in the cAMP-negative strain indicating a coordinated global regulation. The results demonstrate that cAMP is crucial for catabolic flexibility during slow, carbon-limited growth, whereas RpoS is primarily involved in the regulation of stress response systems necessary for the survival of this bacterium under hunger conditions.

Uptake of 4-Toluene Sulfonate by Comamonas testosteroni T-2

Abstract: The mechanism of transport of the xenobiotic 4-toluene sulfonate (TS) in Comamonas testosteroni T-2 was investigated. Rapid uptake of TS was observed only in cells grown with TS or 4-methylbenzoate as a carbon and energy source. Initial uptake rates under aerobic conditions showed substrate saturation kinetics, with an apparent affinity constant (Kt) of 88 microM and a maximal velocity (Vmax) of 26.5 nmol/min/mg of protein. Uptake of TS was inhibited completely by uncouplers and only marginally by ATPase inhibitors and the phosphate analogs arsenate and vanadate. TS uptake was also studied under anaerobic conditions, which prevented intracellular TS metabolism. TS was accumulated under anaerobic conditions in TS-grown cells upon imposition of an artificial transmembrane pH gradient (delta pH, inside alkaline). Uptake of TS was inhibited by structurally related methylated and chlorinated benzenesulfonates and benzoates. The results provide evidence that the first step in the degradation of TS by C. testosteroni T-2 is uptake by an inducible secondary proton symport system.

Doppler tomography of the Little Homunculus: high‐resolution spectra of [Fe II]λ16 435 around Eta Carinae★

Abstract: High-resolution spectra of [Fe II ] λ16435 around η Carinae provide powerful diagnostics of the geometry and kinematics of the 'Little Homunculus' (LH) growing inside the larger Homunculus nebula. The LH expansion is not perfectly homologous: while low latitudes are consistent with linear expansion since 1910, the polar caps imply ejection dates around 1920-1930. However, the expansion speed of the LH is much slower than the post-eruption wind, so the star's powerful wind may accelerate the LH. With an initial ejection speed of 200 km s -1 in 1890, the LH would have been accelerated to its present speed if the mass is roughly 0.1 M ○. . This agrees with an independent estimate of the LH mass based on its density and volume. In any case, an ejection after 1930 is ruled out. Using the LH as a probe of the 1890 event then, it is evident that its most basic physical parameters (total mass and kinetic energy, which are 0.1 M ○. and 10 46.9 erg, respectively) are orders of magnitude less than during the giant eruption in the 1840s. Thus, the ultimate energy sources were different for these two events - yet their ejecta have the same bipolar geometry. This clue may point toward a collimation mechanism separate from the underlying causes of the outbursts.

Use of cyanocobalamin to enhance anaerobic biodegradation of chloroform.

Abstract: Biodegradation of chloroform (CF) was examined in a methanogenic enrichment culture grown on dichloromethane (DCM) as the sole organic carbon and energy source, with and without the addition of supplemental cyanocobalamin In the absence of cyanocobalamin, the principal products of P4C1 CF biodegradation were 14C02 and V4C1DCM The extent of CF reduction to DCM increased significantly when CF was biodegraded in the presence of a large amount of DCM The addition of cyanocobalamin enhanced CF biodegradation in two ways First, the rate of CF biodegradation increased approximately 10-fold Second, the metallocofactor increased the extent of CF oxidation to C02 and virtually eliminated the accumulation of DCM These effects were not observed in autoclaved cultures supplemented with cyanocobalamin When cyanocobalamin was added to viable cultures, as much as 10 % of the [l4C1CF transformed accumulated as 14C-labeled carbon monoxide This suggested that the oxidation of CF to C02 proceeds via net hydrolysis to CO CF levels as high as 22 mM were readily transformed, without accumulation of DCM, at cyanocobalamin to CF molar ratios of 3-596 Although the organism or consortium responsible for CF biodegradation was not identified, prior work with DCM suggests that acetogenic bacteria are involved