Construction of hollow and mesoporous ZnO microsphere: a facile synthesis and sensing property.

Mesoporous and hollow structure have been attracting increasing attention for their special properties and potential applications. Here we show a facile fabrication of hollow and mesoporous ZnO microsphere via a one-step wet chemical process using polyethylene glycol (PEG, MW 200) as the solvent and soft template. The morphology and structure of the products were characterized by using scanning electron microscopy and X-ray powder diffraction techniques. Thermal analysis and Fourier transform infrared spectroscopy techniques were also performed to show the properties of the precursor and annealed product. A possible growth mechanism of hollow and mesoporous ZnO microsphere was also proposed. The Brunauer-Emmett-Teller surface area of ZnO microsphere is 28.5 m(2)g(-1) and the size of mesopores is about 10 nm. The Photoluminescence spectra of the as-synthesized ZnO hollow microspheres were also presented. The mesoporous and hollow structure enhance the gas sensitivity of ZnO microsphere, and the obtained ZnO microspheres based sensor has an excellent performance for precision detection of ethanol and acetone with low concentration.

LuxS-dependent AI-2 regulates versatile functions in Enterococcus faecalis V583.

Bacteria utilize a quorum sensing (QS) system to coordinate gene expression by monitoring the concentration of molecules known as autoinducers (AI). In the present study, we confirmed the presence of a LuxS/AI-2 dependent QS system in vancomycin-resistant Enterococcus faecalis V583. Then, the cellular targets controlled by AI-2 were identified by comparative proteomics analysis in order to elucidate the possible role of AI-2 in E. faecalis. Results demonstrated 15 proteins that are differentially expressed upon the addition of AI-2, including proteins involved in metabolism, translation, energy production and/or conversion, and cell wall biogenesis. Glyceraldehyde-3-phosphate dehydrogenase and malate dehydrogenase associated with carbohydrate metabolism and energy production were up-regulated upon inducing by AI-2. In addition, externally added AI-2 could down-regulate acetyl-coenzyme A carboxylase and ornithine carbamoyltransferase, two key enzyme involved in metabolism. All these data suggest that AI-2 signaling may play a role in the regulation of a number of important metabolic properties of E. faecali. We further investigated the role of AI-2 in biofilm formation by E. faecalis, showing the addition of AI-2 to E. faecalis V583 cultures resulted in increased biofilm formation. Our results provide important clues to the role of a LuxS/AI-2 dependent QS system in vancomycin-resistant E. faecalis.

Proteomic analysis of clinical isolate of Stenotrophomonas maltophilia with blaNDM-1, blaL1 and blaL2 ß-lactamase genes under imipenem treatment.

The co-occurrence of L1 and AmpR-L2 with bla(NDM-1) gene with an upstream 250-bp promoter was detected in a clinical isolate of Stenotrophomonas maltophilia DCPS-01, which was resistant to all ß-lactams and sensitive only to colistin and fluoroquinolones. To investigate expression of resistance genes and the molecular mechanisms of bacteria resistance to carbapenems, proteomic profiles of the isolate was passaged with and without the drug by using 2D-PAGE. The results showed that 33 genes exhibiting a ≥3-fold change were identified as candidates that may help S. maltophilia survive drug selection. Strikingly, L1 was expressed more highly in cells grown with imipenem, and the abundant NDM-1 further increased, while very little L2 was detected even following induction. Specific activities for ß-lactamase revealed that L2 remained at constitutive low levels (10.6 U/mg), while L1 and NDM-1 showed clear activity (69.8 U/mg). Our data support that imipenem could specifically and reversibly induce L1 and NDM-1, which together played key roles in drug resistance in DCPS-01. Although NDM-1 mediated resistance to carbapenems has been found in very few cases, to our knowledge, this is the first proteomics research of S. maltophilia with NDM-1, giving very broad-spectrum antibiotic resistance profiles.

Sensitive and rapid detection of the new Delhi metallo-beta-lactamase gene by loop-mediated isothermal amplification.

New Delhi metallo-ß-lactamase 1 (NDM-1), which is associated with resistance to carbapenem, was first reported in 2008. A sensitive and rapid molecular assay to detect the plasmid bla(NDM-1) in clinical isolates is needed to control its spread. We describe a loop-mediated isothermal amplification (LAMP) assay for the rapid detection of bla(NDM-1) from pure culture and sputum, urine, and fecal samples. Eight sets of primers were designed to recognize six or eight distinct sequences on target bla(NDM-1), and one set was selected as the most appropriate set of primers for its rapid detection. The specificity and sensitivity of the primers in the LAMP reactions for bla(NDM-1) detection were determined. The sensitivity of the LAMP assay for bla(NDM-1) detection in sputum, urine, and fecal samples was also tested. Two methods, namely, monitoring of turbidity and addition of calcein to the reaction tube, were used to determine negative and positive results. The results showed that target DNA was amplified and visualized by the two detection methods within 70 min at an isothermal temperature of 65°C. The sensitivity of LAMP, with a detection limit of 10.70 pg/µl DNA, was 100-fold greater than that of PCR. Thirteen infection bacterial strains without bla(NDM-1) were selected for testing of specificity, and the results of the amplification were negative, which showed that the primers had good levels of specificity. The LAMP method reported here is demonstrated to be a potentially valuable means for the detection of bla(NDM-1) and rapid clinical diagnosis, being fast, simple, and low in cost.

Fructose uptake in Bifidobacterium longum NCC2705 is mediated by an ATP-binding cassette transporter.

Recently, a putative ATP-binding cassette (ABC) transport system was identified in Bifidobacterium longum NCC2705 that is highly up-regulated during growth on fructose as the sole carbon source. Cloning and expression of the corresponding ORFs (bl0033-0036) result in efficient fructose uptake by bacteria. Sequence analysis reveals high similarity to typical ABC transport systems and suggests that these genes are organized as an operon. Expression of FruE is induced by fructose, ribose, or xylose and is able to bind these sugars with fructose as the preferred substrate. Our data suggest that BL0033-0036 constitute a high affinity fructose-specific ABC transporter of B. longum NCC2705. We thus suggest to rename the coding genes to fruEKFG and the corresponding proteins to FruE (sugar-binding protein), FruK (ATPase subunit), FruF, and FruG (membrane permeases). Furthermore, protein-protein interactions between the components of the transporter complex were determined by GST pulldown and Western blot analysis. This revealed interactions between the membrane subunits FruF and FruG with FruE, which in vivo is located on the external side of the membrane, and with the cytoplasmatic ATPase FruK. This is in line with the proposed model for bacterial ABC sugar transporters.

Proteomics analysis of Bifidobacterium longum NCC2705 growing on glucose, fructose, mannose, xylose, ribose, and galactose.

To investigate the molecular mechanisms underlying carbohydrate uptake and connected metabolic pathways of Bifidobacterium longum NCC2705, the proteomic profiles of bacteria grown on different carbon sources including glucose, fructose, mannose, xylose, ribose, and galactose were analyzed. Our results show that all sugars tested were catabolized via the bifid shunt. Sixty-eight proteins that exhibited changes in abundance of threefold or greater were identified by MS. A striking observation was the differential expression of proteins related to the pyruvate metabolism. Further analysis of acetic acid and lactic acid in the culture supernatants by HPLC at the end of fermentation showed that more lactic acid was produced during growth on fructose, ribose, xylose, galactose and more acetic acid was produced during the fermentation of glucose and mannose. Growth experiments revealed that B. longum NCC2705 preferentially used fructose, ribose, xylose, and galactose with higher growth rates over glucose and mannose. Furthermore, five proteins (GroEL, Eno, Tal, Pgm, and BL0033) exhibited clear phosphorylation modifications at serine and/or tyrosine residues. BL0033, a component of an ATP-binding cassette (ABC) transporter, was significantly more abundant in bacteria grown on fructose and, to a lesser extent, ribose and xylose. RT-PCR analysis revealed that all genes of the ABC transporter are induced in the presence of these sugars suggesting that BL0033, BL0034, BL0035, and BL0036 constitute an ABC transporter with fructose as preferred substrate.