United States Department of Energy

About: United States Department of Energy is a government organization based out in Washington D.C., District of Columbia, United States. It is known for research contribution in the topics: Coal & Catalysis. The organization has 13656 authors who have published 14177 publications receiving 556962 citations. The organization is also known as: DOE & Department of Energy.

Comparative metagenomic and metatranscriptomic analysis of hindgut paunch microbiota in wood- and dung-feeding higher termites

Abstract: Termites effectively feed on many types of lignocellulose assisted by their gut microbial symbionts. To better understand the microbial decomposition of biomass with varied chemical profiles, it is important to determine whether termites harbor different microbial symbionts with specialized functionalities geared toward different feeding regimens. In this study, we compared the microbiota in the hindgut paunch of Amitermes wheeleri collected from cow dung and Nasutitermes corniger feeding on sound wood by 16S rRNA pyrotag, comparative metagenomic and metatranscriptomic analyses. We found that Firmicutes and Spirochaetes were the most abundant phyla in A. wheeleri, in contrast to N. corniger where Spirochaetes and Fibrobacteres dominated. Despite this community divergence, a convergence was observed for functions essential to termite biology including hydrolytic enzymes, homoacetogenesis and cell motility and chemotaxis. Overrepresented functions in A. wheeleri relative to N. corniger microbiota included hemicellulose breakdown and fixed-nitrogen utilization. By contrast, glycoside hydrolases attacking celluloses and nitrogen fixation genes were overrepresented in N. corniger microbiota. These observations are consistent with dietary differences in carbohydrate composition and nutrient contents, but may also reflect the phylogenetic difference between the hosts.

Mode of action of liver tumor induction by trichloroethylene and its metabolites, trichloroacetate and dichloroacetate.

Abstract: Trichloroethylene (TCE) induces liver cancer in mice but not in rats Three metabolites of TCE may contribute--chloral hydrate (CH), dichloroacetate (DCA), and trichloroacetate (TCA) CH and TCA appear capable of only inducing liver tumors in mice, but DCA is active in rats as well The concentrations of TCA in blood required to induce liver cancer approach the mM range Concentrations of DCA in blood associated with carcinogenesis are in the sub-microM range The carcinogenic activity of CH is largely dependent on its conversion to TCA and/or DCA TCA is a peroxisome proliferator in the same dose range that induces liver cancer Mice with targeted disruptions of the peroxisome proliferator-activated receptor alpha (PPAR-alpha) are insensitive to the liver cancer-inducing properties of other peroxisome proliferators Human cells do not display the responses associated with PPAR-alpha that are observed in rodents This may be attributed to lower levels of expressed PPAR-alpha in human liver DCA treatment produces liver tumors with a different phenotype than TCA Its tumorigenic effects are closely associated with differential effects on cell replication rates in tumors, normal hepatocytes, and suppression of apoptosis Growth of DCA-induced tumors has been shown to arrest after cessation of treatment The DCA and TCA adequately account for the hepatocarcinogenic responses to TCE Low-level exposure to TCE is not likely to induce liver cancer in humans Higher exposures to TCE could affect sensitive populations Sensitivity could be based on different metabolic capacities for TCE or its metabolites or result from certain chronic diseases that have a genetic basis

Vibrational frequencies and structural properties of transition metals via total-energy calculations

Abstract: The vibrational frequencies of selected normal modes can be obtained entirely from first principles with use of frozen phonon calculations which involve the precise evaluation of crystal total energy as a function of lattice displacement. The calculations allow a detailed analysis of the microscopic mechanisms causing phonon anomalies and soft-mode phase transitions. Successful calculations for Zr, Nb, and Mo have been made with use of both tight-binding and pseudopotential methods.

Envisioning the Bioconversion of Methane to Liquid Fuels

Abstract: Efforts to use natural gas in transportation, either directly or by conversion to a liquid fuel, have been spurred by recent increases in available supply and a growing price spread between natural gas and petroleum, especially in the United States ( 1 ). Conversion of natural gas-to-liquids (GTL) can take advantage of existing engine and delivery infrastructure, but GTL approaches operate on scales similar to that of petroleum refineries and suffer from low energy and carbon efficiencies, as well as high capital cost ( 2 ). Small-scale methane sources that are often flared or vented and that add greenhouse gas emissions also need an economical route for recovery. Biological methane conversion has the potential to directly activate methane at ambient temperatures and pressures on a scale similar to that of sugar fermentation ( 3 ) and could circumvent partial oxidation routes used industrially that dominate costs and reduce efficiency. Further process simplification is possible by one-step conversion, producing a single-molecule product and reducing the need for heat integration.