Construction of Listeria monocytogenes Mutants with In‐Frame Deletions in the Phosphotransferase Transport System (PTS) and Analysis of Their Growth under Stress Conditions

Listeria monocytogenes is a foodborne pathogen that is difficult to eliminate due to its ability to survive under different stress conditions such as low pH and high salt. To better control this pathogen in food, it is important to understand its survival mechanisms under these stress conditions. LMOf2365_0442, 0443, and 0444 encode for phosphotransferase transport system (PTS) permease (fructose‐specific IIABC components) that is responsible for sugar transport. LMOf2365_0445 encodes for glycosyl hydrolase. These genes were induced by high pressure and inhibited under salt treatments; therefore, we hypothesized that genes encoding these PTS proteins may be involved in general stress responses. To study the function of these genes, deletion mutants of the PTS genes (LMOf2365_0442, LMOf2365_0443, and LMOf2365_0444) and the downstream gene LMOf2365_0445 were created in L. monocytogenes strain F2365. These deletion mutants were tested under different stress conditions. The growth of ?LMOf2365_0445 was increased under nisin (125 μg/mL) treatments compared to the wild‐type (P < 0.01). The growth of ?LMOf2365_0442 in salt (brain–heart infusion medium with 5% NaCl) was significantly increased (P < 0.01), and ?LMOf2365_0442 showed increased growth under acidic conditions (pH 5.0) compared to the wild‐type (P < 0.01). The results from phenotypic arrays demonstrated that some of these mutants showed slightly slower growth under different carbon sources and basic conditions. The results indicate that deletion mutants ?LMOf2365_0442 and ?LMOf2365_0445 were more resistant to multiple stress conditions compared to the wild‐type, suggesting that they may contribute to the general stress response in L. monocytogenes. An understanding of the growth of these mutants under multiple stress conditions may assist in the development of intervention strategies to control L. monocytogenes in food.     

Polyphenolic composition in different parts of some cultivars of globe artichoke (Cynara cardunculus L. var. scolymus (L.) Fiori)

The analysis of polyphenols of leaves and different parts (outer, intermediate and inner bracts, and receptacle) of heads in five globe artichoke cultivars of Campania region (Italy) and one accession of cultivated cardoon was performed. Data obtained suggest that the edible parts (receptacles with inner and intermediate bracts) of these cultivars of artichoke could represent a good source of health-promoting polyphenols and therefore encourage a nutriceutical use of this species, as an alternative to the more traditional phytopharmaceutical applications of leaf extracts. Moreover, it was demonstrated that single polyphenols accumulate preferentially in specific parts of the heads and in specific genotypes.     

Skype‐Hunter: A real‐time system for the detection and classification of Skype traffic

In the previous years, Skype has gained more and more popularity, since it is seen as the best VoIP software with good quality of sound, ease of use and one that works everywhere and with every OS. Because of its great diffusion, both the operators and the users are, for different reasons, interested in detecting Skype traffic. In this paper we propose a real‐time algorithm (named Skype‐Hunter) to detect and classify Skype traffic. In more detail, this novel method, by means of both signature‐based and statistical procedures, is able to correctly reveal and classify the signaling traffic as well as the data traffic (calls and file transfers). To assess the effectiveness of the algorithm, experimental tests have been performed with several traffic data sets, collected in different network scenarios. Our system outperforms the ‘classical’ statistical traffic classifiers as well as the state‐of‐the‐art ad hoc Skype classifier. Copyright © 2011 John Wiley & Sons, Ltd.     

Identification of Vegetable Oil or Biodiesel Added to Diesel Using Fluorescence Spectroscopy and Principal Component Analysis

In order to identify possible adulteration of onroad diesel with vegetable oil, fluorescence spectroscopy was used as the analytical technique to differentiate between vegetable oil and biodiesel in diesel blends. Diesel/oil and diesel/biodiesel blends made with different proportions of soy, canola or waste cooking oil were analyzed. The reduced cost of analysis using fluorescence spectroscopy together with the reliability of the results suggest that this technique could be of great use in differentiating between diesel, biodiesel and vegetable oil and could therefore be used for rapid identification or confirmation of adulterated diesel. Furthermore, a compact fluorescence spectrophotometer with an LED excitation source could be used in gas stations or fuel distributors for diesel quality control because of its practicality, low cost and reliability.     

Synthesis and characterization of electrically conductive polyethylene-supported graphene films

We describe a simple mechanical approach for low-density polyethylene film coating by multilayer graphene. The technique is based on the exfoliation of nanocrystalline graphite (few-layer graphene) by application of shear stress and allows to obtain thin graphene layers on the plastic substrate. We report on the temperature dependence of electrical resistance behaviors in films of different thickness. The experimental results suggest that the semiconducting behavior observed at low temperature can be described in the framework of the Efros-Shklovskii variable-range-hopping model. The obtained films exhibit good electrical conductivity and transparency in the visible spectral region.

PACS

72.80.Vp; 78.67.Wj; 78.66.Qn; 85.40.Hp     

Xylose Fermentation by Saccharomyces cerevisiae: Challenges and Prospects

Many years have passed since the first genetically modified Saccharomyces cerevisiae strains capable of fermenting xylose were obtained with the promise of an environmentally sustainable solution for the conversion of the abundant lignocellulosic biomass to ethanol. Several challenges emerged from these first experiences, most of them related to solving redox imbalances, discovering new pathways for xylose utilization, modulation of the expression of genes of the non-oxidative pentose phosphate pathway, and reduction of xylitol formation. Strategies on evolutionary engineering were used to improve fermentation kinetics, but the resulting strains were still far from industrial application. Lignocellulosic hydrolysates proved to have different inhibitors derived from lignin and sugar degradation, along with significant amounts of acetic acid, intrinsically related with biomass deconstruction. This, associated with pH, temperature, high ethanol, and other stress fluctuations presented on large scale fermentations led the search for yeasts with more robust backgrounds, like industrial strains, as engineering targets. Some promising yeasts were obtained both from studies of stress tolerance genes and adaptation on hydrolysates. Since fermentation times on mixed-substrate hydrolysates were still not cost-effective, the more selective search for new or engineered sugar transporters for xylose are still the focus of many recent studies. These challenges, as well as under-appreciated process strategies, will be discussed in this review.     

Isolation of a 25-kDa protein binding to a curved DNA upstream the origin of the L strand replication in the rat mitochondrial genome

The presence of a curved DNA sequence in the gene for the NADH-dehydrogenase subunit 2 of rat mitochondrial genome, upstream from the origin of the light strand replication have been demonstrated through theoretical analysis and experimental approaches. Gel retardation assays showed that this structure makes a complex with a protein component extracted from the mitochondrial matrix. The isolation and purification of this protein is reported. With a Sepharose CL-6B and magnetic DNA affinity chromatography a polypeptide was purified to homogeneity having 25-kDa mass as shown by gel electrophoresis. To functionally characterize this protein, its capability to bind to other sequences of the homologous or heterologous DNA and to specific riboprobes was also investigated. A role for this protein as a trans-acting agent required for the expression of the mammalian mitochondrial genome is suggested.     

Automated system to acquire fluorescence, polarization and anisotropy maps within liquid flows

Maps of polarization and anisotropy can be helpful for flow analysis systems (FIA, CFA, etc.) with reactions dependent on the intermolecular alignment as well as for dispersion control. Maps can be acquired manually, but when a scan over a sample area is required, the acquisition becomes tiresome and has low precision. The paper describes an automatic flexible system for high-precision sample positioning with closed loop self control, remote data acquisition and storage controlled by a BASIC program. The system was developed to acquire maps up to 850 mm(2) of the sample (liquid flows, solids, interfaces, etc.), with up to 100 mum(2) precision. To evaluate the equipment, performance is presented as the scan of a thin liquid film of monoethylene glycol (MEG) flowing on borosilicate. Tests were performed with and without surfactantes at submicellar concentrations: two concentrations of sodium dodecyl sulphate (SDS) and one of polyethylene oxide (PEO). For pure MEG, the intermolecular alignment initially increased, then decreased. When SDS was added, both polarization and anisotropy only increased progressively with the flow. This might be explained by the surfactant decrease of interfacial interaction. When PEO was added, both polarization and anisotropy decreased pronouncedly over the entire map, which might be due to macromolecular aggregates within the bulk generating misaligned molecular domains. The system presented as sample positioning repeatability of 0.1% and a high polarization reproducibility (error margin < 6 in 1000).