Surface Roughness of Commercial Composites after Different Polishing Protocols: An Analysis with Atomic Force Microscopy

Polishing may increase the surface roughness of composites, with a possible effect on bacterial growth and material properties. This preliminary in vitro study evaluates the effect of three different polishing systems (PoGo polishers, Enhance, Venus Supra) on six direct resin composites (Gradia Direct, Venus, Venus Diamond, Enamel Plus HFO, Tetric Evoceram, Filtek Supreme XT)

Whole genome sequencing of Saccharomyces cerevisiae: from genotype to phenotype for improved metabolic engineering applications

<p>Abstract</p> <p>Background</p> <p>The need for rapid and efficient microbial cell factory design and construction are possible through the enabling technology, metabolic engineering, which is now being facilitated by systems biology approaches. Metabolic engineering is often complimented by directed evolution, where selective pressure is applied to a partially genetically engineered strain to confer a desirable phenotype. The exact genetic modification or resulting genotype that leads to the improved phenotype is often not identified or understood to enable further metabolic engineering.</p> <p>Results</p> <p>In this work we performed whole genome high-throughput sequencing and annotation can be used to identify single nucleotide polymorphisms (SNPs) between <it>Saccharomyces cerevisiae </it>strains S288c and CEN.PK113-7D. The yeast strain S288c was the first eukaryote sequenced, serving as the reference genome for the <it>Saccharomyces </it>Genome Database, while CEN.PK113-7D is a preferred laboratory strain for industrial biotechnology research. A total of 13,787 high-quality SNPs were detected between both strains (reference strain: S288c). Considering only metabolic genes (782 of 5,596 annotated genes), a total of 219 metabolism specific SNPs are distributed across 158 metabolic genes, with 85 of the SNPs being nonsynonymous (e.g., encoding amino acid modifications). Amongst metabolic SNPs detected, there was pathway enrichment in the galactose uptake pathway (<it>GAL1</it>, <it>GAL10</it>) and ergosterol biosynthetic pathway (<it>ERG8</it>, <it>ERG9</it>). Physiological characterization confirmed a strong deficiency in galactose uptake and metabolism in S288c compared to CEN.PK113-7D, and similarly, ergosterol content in CEN.PK113-7D was significantly higher in both glucose and galactose supplemented cultivations compared to S288c. Furthermore, DNA microarray profiling of S288c and CEN.PK113-7D in both glucose and galactose batch cultures did not provide a clear hypothesis for major phenotypes observed, suggesting that genotype to phenotype correlations are manifested post-transcriptionally or post-translationally either through protein concentration and/or function.</p> <p>Conclusions</p> <p>With an intensifying need for microbial cell factories that produce a wide array of target compounds, whole genome high-throughput sequencing and annotation for SNP detection can aid in better reducing and defining the metabolic landscape. This work demonstrates direct correlations between genotype and phenotype that provides clear and high-probability of success metabolic engineering targets. The genome sequence, annotation, and a SNP viewer of CEN.PK113-7D are deposited at <url>http://www.sysbio.se/cenpk</url>.</p

In vivo Hypoxia and a Fungal Alcohol Dehydrogenase Influence the Pathogenesis of Invasive Pulmonary Aspergillosis

Currently, our knowledge of how pathogenic fungi grow in mammalian host environments is limited. Using a chemotherapeutic murine model of invasive pulmonary aspergillosis (IPA) and 1H-NMR metabolomics, we detected ethanol in the lungs of mice infected with Aspergillus fumigatus. This result suggests that A. fumigatus is exposed to oxygen depleted microenvironments during infection. To test this hypothesis, we utilized a chemical hypoxia detection agent, pimonidazole hydrochloride, in three immunologically distinct murine models of IPA (chemotherapeutic, X-CGD, and corticosteroid). In all three IPA murine models, hypoxia was observed during the course of infection. We next tested the hypothesis that production of ethanol in vivo by the fungus is involved in hypoxia adaptation and fungal pathogenesis. Ethanol deficient A. fumigatus strains showed no growth defects in hypoxia and were able to cause wild type levels of mortality in all 3 murine models. However, lung immunohistopathology and flow cytometry analyses revealed an increase in the inflammatory response in mice infected with an alcohol dehydrogenase null mutant strain that corresponded with a reduction in fungal burden. Consequently, in this study we present the first in vivo observations that hypoxic microenvironments occur during a pulmonary invasive fungal infection and observe that a fungal alcohol dehydrogenase influences fungal pathogenesis in the lung. Thus, environmental conditions encountered by invading pathogenic fungi may result in substantial fungal metabolism changes that influence subsequent host immune responses

Effect of chemical degradation followed by toothbrushing on the surface roughness of restorative composites

OBJECTIVES: The aim of the present study was to assess the effect of the exposure to food-simulating liquids prior to brushing simulation on the surface roughness of five composite materials (Quixfil, Filtek Supreme, Esthet-X, Filtek Z250, Tetric Ceram). MATERIAL AND METHODS: Twenty cylinders (5 mm diameter and 4 mm height) of each composite were randomly allocated to 4 groups (n=5), according to the food-simulating liquid in which they were immersed for 7 days at 37ºC: artificial saliva, heptane, citric acid, and ethanol. After this period, the top surface of composite cylinders was submitted to 7,500 brushing cycles (200 g load). Measurements of the surface roughness (Ra, µm) were carried out before and after the exposure to the chemicals/brushing simulation. Changes on the morphology of composite surfaces were observed through scanning electron microscopy (SEM). RESULTS: The statistical analysis (ANOVA with cofactor / Tukey's test, α=5%) detected a significant interaction between solutions and composite resins. Esthet-X, Filtek Z250 and Tetric Ceram were not affected by the food-simulating liquids/toothbrushing. Citric acid and ethanol increased the surface roughness of Quixfil and Filtek Supreme, respectively. SEM images corroborate the surface roughness findings, demonstrating the negative effect from chemical solutions and mechanical abrasion. CONCLUSIONS: The surface roughness of composite resin materials are differently affected by the food-simulating solutions, depending on the immersion media