Carbon and sulfur cycling by microbial communities in a gypsum-treated oil sands tailings pond

Oil sands tailings ponds receive and store the solid and liquid waste from bitumen extraction and are managed to promote solids densification and water recycling. The ponds are highly stratified due to increasing solids content as a function of depth but can be impacted by tailings addition and removal and by convection due to microbial gas production. We characterized the microbial communities in relation to microbial activities as a function of depth in an active tailings pond routinely treated with gypsum (CaSO(4)·2H(2)O) to accelerate densification. Pyrosequencing of 16S rDNA gene sequences indicated that the aerobic surface layer, where the highest level of sulfate (6 mM) but no sulfide was detected, had a very different community profile than the rest of the pond. Deeper anaerobic layers were dominated by syntrophs (Pelotomaculum, Syntrophus, and Smithella spp.), sulfate- and sulfur-reducing bacteria (SRB, Desulfocapsa and Desulfurivibrio spp.), acetate- and H(2)-using methanogens, and a variety of other anaerobes that have been implicated in hydrocarbon utilization or iron and sulfur cycling. The SRB were most abundant from 10 to 14 mbs, bracketing the zone where the sulfate reduction rate was highest. Similarly, the most abundant methanogens and syntrophs identified as a function of depth closely mirrored the fluctuating methanogenesis rates. Methanogenesis was inhibited in laboratory incubations by nearly 50% when sulfate was supplied at pond-level concentrations suggesting that in situ sulfate reduction can substantially minimize methane emissions. Based on our data, we hypothesize that the emission of sulfide due to SRB activity in the gypsum treated pond is also limited due to its high solubility and oxidation in surface waters.     

Isolation and characterization of a Δ-9 fatty acid desaturase gene from the oleaginous yeast Cryptococcus curvatus CBS 570

The oleaginous yeast Cryptococcus curvatus is of industrial interest because it can accumulate triacylglycerols up to 60% of the cell dry weight. We are aiming at genetic modification of fatty acid biosynthesis for the production of tailor-made triacylglycerols in C. curvatus. As a first step in the development of a transformation and expression system a gene encoding the Δ-9 fatty acid desaturase of C. curvatus (CBS 570) was cloned. The 1470 bp gene encodes a protein of 493 amino acids with a calculated molecular mass of 55 kDa. The gene shows strong similarity to previous cloned Δ-9 desaturase genes from rat and Saccharomyces cerevisiae, 62 and 72%, respectively. Expression of the Δ-9 desaturase gene was studied. Supplementation of the growth medium with oleic acid (C18:1(c9)) showed a strong repression (90%) on the mRNA level, while supplementation with petroselinic acid (C18:1(c6)) had no effect on the amount of mRNA.     

On the Origin of a Low Angle Spacing in Starch

The structure of starch granules from different botanical sources was studied by transmission electron microscopy and small-angle X-ray diffraction. Electron micrographs of negatively stained starch granule fragments show a rippled fibrous structure. The ripples are interpreted as being stacks of thin crystalline lamellae comprising the linear α-(1→4) chains of the amylopectin. Optical diffraction analysis of the electron micrographs showed that the spacing of the ripples varies from 9.2 nm in potato starch to 10.4 nm in barley starch. This correlates well with the position of a Bragg peak at appr. 10 nm measured by small-angle X-ray diffraction. These observations indicate that the Bragg peak arises from the alternating amorphous and crystalline regions seen as ripples in the electron micrographs.     

Inverse wave field extrapolation: a different NDI approach to imaging defects

Nondestructive inspection (NDI) based on ultrasound is widely used. A relatively recent development for industrial applications is the use of ultrasonic array technology. Here, ultrasonic beams generated by array transducers are controlled by a computer. This makes the use of arrays more flexible than conventional single-element transducers. However, the inspection techniques have principally remained unchanged. As a consequence, the properties of these techniques, as far as characterization and sizing are concerned, have not improved. For further improvement, in this paper we apply imaging theory developed for seismic exploration of oil and gas fields on the NDI application. Synthetic data obtained from finite difference simulations is used to illustrate the principle of imaging. Measured data is obtained with a 64-element linear array (4 MHz) on a 20-mm thick steel block with a bore hole to illustrate the imaging approach. Furthermore, three examples of real data are presented, representing a lack of fusion defect, a surface breaking crack, and porosity.     

Einfluss von verarbeitungsbedingungen und additiven auf die abbaureaktionen von SIS-blockcopolymeren

SIS block copolymers are used particularly as polymer component in hot melt adhesives. During compounding at temperatures of 170–180°C undesired viscosity decrease occurs occasionally. For that reason the influence of additives and the role of compounding conditions, particularly the oxygen concentration, on the degradation of SIS has been investigated. It was found that primary antioxidants are unable to reduce the degradation of SIS under anaerobic or oxygen deficient conditions, but they are very effective when excess of oxygen is present in the system (e.g. an open mixer or mill). C-radical scavengers reduce the chain scission reaction at high oxygen concentrations, too, but accelerate the decrease of the molecular weight under inert gas atmosphere.     

Feeding stimulatory and inhibitory chemicals from an acceptable nonhost plant forManduca sexta: Improved detection by larvae deprived of selected chemosensory organs

The chemical basis of feeding responses to the acceptable nonhost plantVigna sinensis (cowpea) by larvae ofManduca sexta was investigated using chemical isolation techniques directed by a novel chemosensory-based bioassay. The presence of feeding stimulatory and inhibitory compounds in leaves or leaf extracts was determined in a two-choice preference test using leaf disks or glass fiber filter paper disks laced with leaf extract as test substrate and filter paper disks laced with water as control. Larvae strongly prefer the control disks over leaf disks, indicating the presence of feeding inhibitory compounds in the leaf. An ethanol extract of both fresh and dried leaves neither stimulated nor inhibited feeding. The cause of this inactivity was examined by using larvae that respond strongly to either feeding stimulatory or inhibitory compounds due to selective chemosensory deprivation. Larvae having chemosensory organs remaining only on the maxillary palps are stimulated to feed by whole leaf disks and by the ethanol extracts. In contrast, larvae having only the medial and lateral maxillary sensilla styloconica and the epipharyngeal sensilla remaining are strongly inhibited by whole leaf disks and the ethanol extract of fresh leaves. Thus, the ethanol extract contains both feeding stimulatory and inhibitory compounds, which elicit opposite behavioral effects in unoperated larvae, therefore nullifying any stimulatory and inhibitory activity. These compounds can only be demonstrated by using discrimination-enhanced larvae in the choice tests. Further isolation of the feeding stimulatory principle inV. sinensis yielded two separate fractions of neutral compounds, suggesting at least two different chemicals belonging to two different classes: nonpolar and polar lipids. Feeding inhibitory chemicals have apparently polar properties because strong activity was found in the ethyl acetate and methanol extracts of dried leaves. The role of feeding stimulatory and inhibitory compounds in food selection ofM. sexta larvae is discussed.     

Introduction of a stabilizing 10 residue {beta}-hairpin in Bacillus subtilis neutral protease

A 10 residue ß-hairpin, which is characteristic ofthermostable Bacillus neutral proteases, was engineered intothe thermolabile neutral protease of Bacillus subtilis. Therecipient enzyme remained fully active after introduction ofthe loop. However, the mutant protein exhibited autocatalyticnicking and a 0.4°C decrease in thermostability. Two additionalpoint mutations designed to improve the interactions betweenthe enzyme surface and the introduced ß-hairpin resultedin reduced nicking and increased thermostability. After theintroduction of both additional mutations in the loopcontainingmutant, nicking was largely prevented and an increase in thermostabilityof 1.1°C was achieved.     

The effect of cavity-filling mutations on the thermostability of Bacillus stearothermophilus neutral protease

Cavities in the hydrophobic core of the neutral protease ofBacillus stearothermophilus were analyzed using a threedimensionalmodel that was inferred from the crystal structure of thermolysin,the highly homologous neutral protease of B.thermoproteolyticus(85% sequence identity). Site–directed mutagenesis wasused to fill some of these cavities, thereby improving hydrophobicpacking in the protein interior. The mutations had small effectson the thermostability, even after drastic changes, such asLeu284Trp and Met168Trp. The effects on T50, the temperatureat which 50% of the enzyme is irreversibly inactivated in 30min, ranged from 0.0 to +0.4°C. These results can be explainedby assuming that the mutations have positive and negative structuraleffects of approximately the same magnitude. Alternatively,it could be envisaged that the local unfolding steps, whichrender the enzyme susceptible towards autolysis and which arerate limiting in the process of thermal inactivation, are onlyslightly affected by alterations in the hydrophobic core.