Autotrophic Growth of Thiobacillus acidophilus in the Presence of a Surface-Active Agent, Tween 80

Cellular protein, pH, dissolved oxygen concentration, and static surface tension were measured during growth of Thiobacillus acidophilus on elemental sulfur in the absence and presence of up to 5,000 mg of Tween 80 per liter. The decrease in pH and the increase in sulfate production were observed to be less accurate measurements of growth when compared with the increase in cellular protein. The doubling time of the bacterium decreased approximately 50% with the addition of 500 mg of Tween 80 per liter. The bacteria did not appear to synthesize any wetting agents as demonstrated by the constant surface tension of the medium during growth. Morphological alterations in the presence of Tween 80 were also observed.     

Growth of Iron-Oxidizing Thiobacilli in the Presence of Chalcopyrite and Galena

Iron-oxidizing thiobacilli were adapted to grow on a chalcopyrite and a galena ore concentrate. When grown on the chalcopyrite concentrate, the bacteria exhibited a doubling time of 38.4 ± 2.9 h, with a final cellular protein concentration of 185 μg/ml and solubilization of 10.3 g of copper per liter. When grown on the galena ore concentrate, the generation time was 39.6 ± 2.7 h, with a final cellular protein concentration of 120 μg/ml. Galena was converted to lead salts soluble in 1 M ammonium acetate to a concentration of 20.2 g of lead per liter. X-ray diffraction and refractive-image analysis indicated that the smaller-sized particles were favored in this process. Galena was converted to anglesite, and soluble copper was liberated from chalcopyrite with the concurrent formation of jarosite.     

Pseudomonas oleovorans as a tool in bioconversions of hydrocarbons: growth,morphology and conversion characteristics in different two-phase systems

The bioconversion of hydrocarbons by Pseudomonas oleovorans has been studied in two-phase systems. In these systems, the hydrocarbon substrate is present in sufficient amounts to form the bulk apolar phase. High cell densities (up to 20 mg dry mass per ml water phase) are reached when the apolar phase consists of n-octane, 1-octene or 1-decene. There is considerable cell damage after incubation for 50–70 h. Loss of cell viability and membrane damage as observed by freeze-fracture electron microscopy correlate with a loss of hydrocarbon oxidation, measured as the conversion of 1-octene to 1,2-epoxyoctane. The final yield of oxidized hydrocarbon in the apolar substrate phase can be increased substantially by replacing the damaged cells with freshly grown cells. Yields up to 150 mg 1,2-epoxyoctane per ml 1-octene and up to 20–25 mg 1,2-epoxyoctane per ml culture were obtained with four cycles of the cell renewal procedure. Several other substrates in addition to octene were tested in the optimized two-phase system. Of these, 1-decene was converted into (R)-1,2-epoxydecane with an optical purity of 60%, while allylbenzene was converted into chiral 1,2-epoxy-3-phenylpropane. Some of the future applications of the conversion products are discussed.     

Reperfusion-induced arrhythmias are not prevented by uric acid in the isolated rat heart

Oxygen-derived free radicals have been implicated in ventricular arrhythmogenesis during coronary reperfusion following an acute ischemic event. We have investigated the possibility that uric acid, a potentially important physiological antioxidant (inhibits lipid peroxidation and scavenges various radical species during oxidation to allantoin), or oxonic acid (inhibitor of uricase enzyme), are able to prevent reperfusion-induced ventricular dysrhythmias in isolated buffer-perfused rat hearts. Rat hearts (n = 12/group) underwent 15 minutes occlusion; arrhythmias were monitored during ischemia and for 10 minutes of reperfusion. There was no difference in the incidence of ventricular fibrillation or ventricular tachycardia in either uric acid or oxonic acid treated hearts compared to untreated controls. Mean duration of ventricular fibrillation appeared to be reduced in hearts treated with 10(-3) and 10(-4) M oxonic acid compared to controls but these data did not achieve a level of statistical significance. These results demonstrate that uric acid and oxonic acid failed to prevent reperfusion-mediated ventricular dysrhythmias in this experimental preparation. Although oxygen-derived free radicals may contribute to the initiation of either ischemia- or reperfusion-induced arrhythmogenesis, our findings provide little support for this hypothesis.     

Improved enantioselective conversion of styrene epoxides and meso-epoxides through epoxide hydrolases with a mutated nucleophile-flanking residue

In epoxide hydrolase from Agrobacterium radiobacter (EchA), phenylalanine 108 flanks the nucleophilic aspartate and forms part of the substrate-binding pocket. The influence of mutations at this position on the activity and enantioselectivity of the enzyme was investigated. Screening for improved enantioselectivity towards para-nitrophenyl glycidyl ether (pNPGE) using spectrophotometric progress curve analysis yielded five different mutants with 3- to 7-fold improved enantioselectivity. The increase in enantioselectivity was in most cases the result of an enhanced catalytic efficiency toward the preferred enantiomer. Several mutations at position F108 resulted in a higher activity toward cis-disubstituted meso-epoxides, which were converted to a single product enantiomer. Mutant F108C converted cis-2,3-epoxybutane to (2R,3R)-2,3-butanediol of >99% ee with a 7-fold improved activity, and mutant F108A hydrolyzed cyclohexene oxide to (1R,2R)-1,2-cyclohexanediol of >99% ee with a more than 150-fold higher activity than wild-type enzyme. It is concluded that single amino acid substitutions in the active site of epoxide hydrolase can result in enzyme variants with catalytic properties that are suitable for preparative scale production of (S)-epoxides and chiral vicinal diols in high yield and with excellent ee.     

Identification of Proteins Secreted by Malaria Parasite into Erythrocyte using SVM and PSSM profiles

Background  

Malaria parasite secretes various proteins in infected RBC for its growth and survival. Thus identification of these secretory proteins is important for developing vaccine/drug against malaria. The existing motif-based methods have got limited success due to lack of universal motif in all secretory proteins of malaria parasite.     

Beschreibung Einiger Neuer Pilzarten aus dem Centraalbureau Voor Schimmelcultures,Baarn (Nederland)

Zusammenfassung Es wurden folgende Pilze im Centraalbureau voor Schimmelcultures zu Baarn neu beschrieben:Arachniotus dankaliense, Penicillium ingelheimense, Phoma suecica, Margarinomyces decumbens, Phialophora atra, Phialophora cyclaminis, Tritirachium cinnamomeum, Tritirachium roseum undCephalosporium lanoso-niveum.

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Terrigenous sediment-dominated reef platform infilling: an unexpected precursor to reef island formation and a test of the reef platform size–island age model in the Pacific

Low-lying coral reef islands are considered highly vulnerable to climate change, necessitating an improved understanding of when and why they form, and how the timing of formation varies within and among regions. Several testable models have been proposed that explain inter-regional variability as a function of sea-level history and, more recently, a reef platform size model has been proposed from the Maldives (central Indian Ocean) to explain intra-regional (intra-atoll) variability. Here we present chronostratigraphic data from Pipon Island, northern Great Barrier Reef (GBR), enabling us to test the applicability of existing regional island evolution models, and the platform size control hypothesis in a Pacific context. We show that reef platform infilling occurred rapidly (~4–5 mm yr⁻¹) under a “bucket-fill” type scenario. Unusually, this infilling was dominated by terrigenous sedimentation, with platform filling and subsequent reef flat formation complete by ~5000 calibrated years BP (cal BP). Reef flat exposure as sea levels slowly fell post highstand facilitated a shift towards intertidal and subaerial-dominated sedimentation. Our data suggest, however, a lag of ~1500 yr before island initiation (at ~3200 cal BP), i.e. later than that reported from smaller and more evolutionarily mature reef platforms in the region. Our data thus support: (1) the hypothesis that platform size acts to influence the timing of platform filling and subsequent island development at intra-regional scales; and (2) the hypothesis that the low wooded islands of the northern GBR conform to a model of island formation above an elevated reef flat under falling sea levels.