Radiation capture and conversion efficiencies of Miscanthus sacchariflorus,M. sinensis and their naturally occurring hybrid M. × giganteus

Miscanthus is a rhizomatous C4 grass of great interest as a biofuel crop because it has the potential to produce high yields over a wide geographical area with low agricultural inputs on marginal land less suitable for food production. At the moment, a clonal interspecific hybrid Miscanthus × giganteus is the most widely cultivated and studied in Europe and the United States, but breeding programmes are developing newer more productive varieties. Here, we quantified the physiological processes relating to whole season yield in a replicated plot trial in Wales, UK. Light capture and conversion efficiency were parameterized for four carefully selected genotypes (M. sinensis, M. sacchariflorus and Miscanthus × giganteus). Differences in the canopy architecture in mature stands as measured by the extinction coefficient (k) were small (0.55–0.65). Sensitivity analysis on a mathematical model of Miscanthus was performed to quantify the accumulative intercepted photosynthetically active radiation (iPAR) in the growing season using (i) k, (ii) variation in the thermal responses of leaf expansion rate, (iii) base temperature for degree days and (iv) date start of canopy expansion. A 10% increase in k or leaf area per degree day both had a minimal effect on iPAR (3%). Decreasing base temperature from 10 to 9 °C gave an 8% increase in iPAR. If the starting date for canopy expansion was the same as shoot emergence date, then the iPAR increases by 12.5%. In M. × giganteus, the whole season above ground and total (including below ground) radiation‐use efficiency (RUE) ranged from 45% to 37% higher than the noninterspecific hybrid genotypes. The greater yields in the interspecific hybrid M. × giganteus are explained by the higher RUE and not by differences in iPAR or partitioning effects. Studying the mechanisms underlying this complex trait could have wide benefits for both fuel and food production.     

Aggregation of amphipathic peptides at an aqueous–organic interface using coarse-grained simulations

The effect of an aqueous/organic interface on the folding and aggregation of amphipathic peptides is examined by applying discontinuous molecular dynamics (DMD) simulations combined with an intermediate resolution protein model, PRIME20, to a peptide/interface system. The systems contain 48 (KLLK)₄ peptides in random coil or α-helical conformations interacting with both strong and weak interfaces. In the absence of an interface, most of the oligomers form helical bundles, a small fraction of which convert to β-sheets when the temperature is above the folding transition. Adding a weak interface decreases oligomer formation above the folding temperature and increases it below. Little monolayer formation is observed at the weak interface; instead reversible adsorption increases the local peptide concentration near the interface, promoting helical bundle formation in the aqueous phase below the folding temperature and β-sheet formation above the folding temperature. Introducing a strong interface leads to irreversible adsorption, promoting formation of helical monolayers below the folding temperature and mixed β-sheet/amorphous monolayers above the folding temperature. The (KLLK)₄ peptide is more likely to adsorb to the interface when it is in an α-helical conformation, as opposed to a random coil, because of its larger hydrophobic moment.     

Bacterial production of free fatty acids from freshwater macroalgal cellulose

The predominant strategy for using algae to produce biofuels relies on the overproduction of lipids in microalgae with subsequent conversion to biodiesel (methyl-esters) or green diesel (alkanes). Conditions that both optimize algal growth and lipid accumulation rarely overlap, and differences in growth rates can lead to wild species outcompeting the desired lipid-rich strains. Here, we demonstrate an alternative strategy in which cellulose contained in the cell walls of multicellular algae is used as a feedstock for cultivating biofuel-producing microorganisms. Cellulose was extracted from an environmental sample of Cladophora glomerata-dominated periphyton that was collected from Lake Mendota, WI, USA. The resulting cellulose cake was hydrolyzed by commercial enzymes to release fermentable glucose. The hydrolysis mixture was used to formulate an undefined medium that was able to support the growth, without supplementation, of a free fatty acid (FFA)-overproducing strain of Escherichia coli (Lennen et. al 2010). To maximize free fatty acid production from glucose, an isopropyl β-D-1-thiogalactopyranoside (IPTG)-inducible vector was constructed to express the Umbellularia californica acyl-acyl carrier protein (ACP) thioesterase. Thioesterase expression was optimized by inducing cultures with 50 μM IPTG. Cell density and FFA titers from cultures grown on algae-based media reached 50% of those (～90 μg/mL FFA) cultures grown on rich Luria-Bertani broth supplemented with 0.2% glucose. In comparison, cultures grown in two media based on AFEX-pretreated corn stover generated tenfold less FFA than cultures grown in algae-based media. This study demonstrates that macroalgal cellulose is a potential carbon source for the production of biofuels or other microbially synthesized compounds.     

Drug induction and sex differences of renal glutathione S-transferases in the rat.

Treatment of male rats with 3,4-benzopyrene, 3-methylcholanthrene and phenobarbital resulted in the induction of glutathione S-aryl- and S-aralkyl-transferase activities in kidney cytosol. Benzopyrene produced 77 and 44% increases in aryl and aralkyl activities respectively. Methylcholanthrene caused 73 and 86% increases in the retrospective activities, whereas phenobarbital treatment increased only aralkyl activity (51%). There was no effect on epoxide or alkyl glutathione S-transferase activities with these treatments. Differences were found between the specific activities of the four glutathione S-transferases in females and males, with the following female/male ratios: aryl 0.74; aralkyl 2.37; epoxide 1.52; alkyl 1.33. No changes in Km values were observed relative to drug induction or sex differences. Comparisons are made between the findings of this report and corresponding experiements with liver.     

Comparison of Two Liquid Blood Culture Media Containing Sodium Polyanetholesulfonate: Tryptic Soy and Columbia

In a comparison of tryptic soy broth and Columbia broth, two blood culture media containing sodium polyanetholesulfonate, there were 589 positive cultures (excluding presumed contaminants). The two media were equivalent in performance except for lower detection rates for Staphylococcus aureus (P < 0.01) and Pseudomonas aeruginosa (P = 0.05) and a higher detection rate for Bacillus (P < 0.01) in Columbia broth. No significant differences were noted in time intervals to detection of positivity. Routine subcultures on the 1st and 5th days of incubation provided the initial detection of 18.1% of the positive cultures.     

Periplasmic Acid Stress Increases Cell Division Asymmetry (Polar Aging) of Escherichia coli

Under certain kinds of cytoplasmic stress, Escherichia coli selectively reproduce by distributing the newer cytoplasmic components to new-pole cells while sequestering older, damaged components in cells inheriting the old pole. This phenomenon is termed polar aging or cell division asymmetry. It is unknown whether cell division asymmetry can arise from a periplasmic stress, such as the stress of extracellular acid, which is mediated by the periplasm. We tested the effect of periplasmic acid stress on growth and division of adherent single cells. We tracked individual cell lineages over five or more generations, using fluorescence microscopy with ratiometric pHluorin to measure cytoplasmic pH. Adherent colonies were perfused continually with LBK medium buffered at pH 6.00 or at pH 7.50; the external pH determines periplasmic pH. In each experiment, cell lineages were mapped to correlate division time, pole age and cell generation number. In colonies perfused at pH 6.0, the cells inheriting the oldest pole divided significantly more slowly than the cells inheriting the newest pole. In colonies perfused at pH 7.50 (near or above cytoplasmic pH), no significant cell division asymmetry was observed. Under both conditions (periplasmic pH 6.0 or pH 7.5) the cells maintained cytoplasmic pH values at 7.2–7.3. No evidence of cytoplasmic protein aggregation was seen. Thus, periplasmic acid stress leads to cell division asymmetry with minimal cytoplasmic stress.     

Validity of Epidemiological Data in Risk Assessment Applications

Data from epidemiological studies might be seen as superior to data from animal bioassays for risk assessment purposes. Because humans are the population of interest, use of epidemiological data avoids interspecies extrapolation. However, one must not assume that an epidemiological study is necessarily valid at face value. We describe issues of validity that arise in the conduct and interpretation of epidemiological research and that affect the utility of epidemiological data in risk assessment. These issues include choice of study design, size and representativeness of the study sample, measurement of exposures and outcomes, control of confounding and specification of statistical model for analysis of data, all of which affect the accuracy and validity of study results.     

Predator driven changes in community structure

Summary The zooplankton community of a small pond changed markedly with temporal variation in predation pressure. Long term changes in zooplankton community structure occurred following the replacement of planktivorous fish by phantom midge (Chaoborus americanus) larvae as the predominant predator of zooplankton. The interannual changes following the establishment of Chaoborus included the apparent or near extinction, of species ill adapted to the new predation pressure and the successful colonization of well adapted species. Seasonal changes in the species composition and size distribution of the zooplankton community correlate with temporal variation in predation intensity associated with temperature-activity patterns of the predator or changes in the stage structure of the predator population.     

Selective Removal of Nitrogen from Quinoline and Petroleum by Pseudomonas ayucida IGTN9m

Enrichment culture experiments employing soil and water samples obtained from petroleum-contaminated environments succeeded in the isolation of a pure culture possessing the ability to utilize quinoline as a sole nitrogen source but did not utilize quinoline as a carbon source. This culture was identified as Pseudomonas ayucida based on a partial 16S rRNA gene sequence, and the strain was given the designation IGTN9m. Examination of metabolites using thin-layer chromatography and gas chromatography-mass spectrometry suggests that P. ayucida IGTN9m converts quinoline to 2-quinolinone and subsequently to 8-hydroxycoumarin. Resting cells of P. ayucida IGTN9m were shown to be capable of selectively removing about 68% of quinoline from shale oil in a 16-h treatment time. These results suggest that P. ayucida IGTN9m may be useful in petroleum biorefining for the selective removal of organically bound nitrogen from petroleum.     

The Erwin equation of biodiversity: From little steps to quantum leaps in the discovery of tropical insect diversity

Almost 40 years ago, Terry L. Erwin published a seemingly audacious proposition: There may be as many as 30 million species of insects in the world. Here, we translate Erwin's verbal argument into a diversity-ratio model—the Erwin Equation of Biodiversity—and discuss how it has inspired other biodiversity estimates. We categorize, describe the assumptions for, and summarize the most commonly used methods for calculating estimates of global biodiversity. Subsequent diversity-ratio extrapolations have incorporated parameters representing empirical insect specialization ratios, and how insect specialization changes at different spatial scales. Other approaches include macroecological diversity models and diversity curves. For many insect groups with poorly known taxonomies, diversity estimates are based on the opinions of taxonomic experts. We illustrate our current understanding of insect diversity by focusing on the six most speciose insect orders worldwide. For each order, we compiled estimates of the (a) maximum estimated number of species, (b) minimum estimated number of species, and (c) number of currently described species. By integrating these approaches and considering new information, we believe an estimate of 5.5 million species of insects in the world is much too low. New molecular methodologies (e.g., metabarcoding and NGS studies) are revealing daunting numbers of cryptic and previously undescribed species, at the same time increasing our precision but also uncertainty about present estimates. Not until technologies advance and sampling become more comprehensive, especially of tropical biotas, will we be able to make robust estimates of the total number of insect species on Earth.