Comprehensive Metabolomic,Lipidomic and Microscopic Profiling of Yarrowia lipolytica during Lipid Accumulation Identifies Targets for Increased Lipogenesis

Yarrowia lipolytica is an oleaginous ascomycete yeast that accumulates large amounts of lipids and has potential as a biofuel producing organism. Despite a growing scientific literature focused on lipid production by Y. lipolytica, there remain significant knowledge gaps regarding the key biological processes involved. We applied a combination of metabolomic and lipidomic profiling approaches as well as microscopic techniques to identify and characterize the key pathways involved in de novo lipid accumulation from glucose in batch cultured, wild-type Y. lipolytica. We found that lipids accumulated rapidly and peaked at 48 hours during the five day experiment, concurrent with a shift in amino acid metabolism. We also report that exhaustion of extracellular sugars coincided with thickening of the cell wall, suggesting that genes involved in cell wall biogenesis may be a useful target for improving the efficiency of lipid producing yeast strains.     

Construction Matters: Comparing Environmental Impacts of Building Modular and Conventional Homes in the United States

Modular construction practices are used in many countries as an alternative to conventional on‐site construction for residential homes. While modular home construction has certain advantages in terms of material and time efficiency, it requires a different infrastructure than conventional home construction, and the overall environmental trade‐offs between the two methods have been unclear. This study uses life cycle assessment to quantify the environmental impacts of constructing a typical residential home using the two methods, based on data from several modular construction companies and conventional homebuilders. The study includes impacts from material production and transport, off‐site and on‐site energy use, worker transport, and waste management. For all categories considered, the average impacts of building the home are less for modular construction than for conventional construction, although these averages obscure significant variation among the individual projects and companies.     

The biogeography of marine plankton traits

Changes in marine plankton communities driven by environmental variability impact the marine food web and global biogeochemical cycles of carbon and other elements. To predict and assess these community shifts and their consequences, ecologists are increasingly investigating how the functional traits of plankton determine their relative fitness along environmental and biological gradients. Laboratory, field and modelling studies are adopting this trait‐based approach to map the biogeography of plankton traits that underlies variations in plankton communities. Here, we review progress towards understanding the regulatory roles of several key plankton functional traits, including cell size, N₂‐fixation and mixotrophy among phytoplankton, and body size, ontogeny and feeding behaviour for zooplankton. The trait biogeographical approach sheds light on what structures plankton communities in the current ocean, as well as under climate change scenarios, and also allows for finer resolution of community function because community trait composition determines the rates of significant processes, including carbon export. Although understanding of trait biogeography is growing, uncertainties remain that stem, in part, from the paucity of observations describing plankton functional traits. Thus, in addition to recommending widespread adoption of the trait‐based approach, we advocate for enhanced collection, standardisation and dissemination of plankton functional trait data.     

Endocytosis of superoxide dismutase is required in order for the enzyme to protect hepatocytes from the cytotoxicity of hydrogen peroxide

Inhibitors of endocytosis have been used to show that internalization of superoxide dismutase is required for the enzyme to protect hepatocytes from the cytotoxicity of hydrogen peroxide. As shown previously (Starke, P. E., and Farber, J. L. (1985) J. Biol. Chem. 260, 10099-10104), superoxide dismutase prevented the killing of cultured hepatocytes by H2O2 generated in the medium by glucose oxidase. Five inhibitors of endocytosis, methylamine, monensin, benzyl alcohol, cytochalasin B, and oligomycin, each abolished the protective effect of superoxide dismutase. Cell-associated superoxide dismutase activity was increased 4-fold in hepatocytes after exposure to superoxide dismutase for 1 h. Each of the inhibitors abolished this increase in the cell-associated superoxide dismutase activity. The uptake of horseradish peroxidase, a measure of fluid phase endocytosis, differed from that of superoxide dismutase in its lower rate, reduced sensitivity to methylamine, and its insensitivity to cytochalasin B. The results of the present study demonstrate that endocytosis of superoxide dismutase is required to protect hepatocytes from the cytotoxicity of hydrogen peroxide. This conclusion may account for some of the conflicting results in the literature with respect to the protective action of superoxide dismutase.     

Ethanol-induced changes in methionine metabolism in rat liver

The administration of alcohol to rats fed a protein-restricted diet results in significant changes in the hepatic content of four enzymes of methionine metabolism. The levels of s-adenosylmethionine synthetase, cystathionine synthase, and betaine-homocysteine methyltransferase increase while the level of methyltetrahydrofolate-homocysteine methyltransferase decreases. These changes represent a reversal of the normal adaptive response to protein-restriction. The resultant impairment in methionine conservation could explain the alcohol-induced increase in the dietary lipotrope requirement.