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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.

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 β-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 β-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.

Here, mixed-phase TiO2 nanorods assembled microspheres were fabricated via a facile one-step hydrothermal process. The synthesized samples were investigated employing X-ray powder diffraction (XRD), Raman spectrometry, field emission-scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM). The study shows the interesting symbiotic phenomenon occurred in the mixed anatase and rutile phase TiO2. The mixed crystalline phase of anatase–rutile ratios were accurately tuned by adjusting the concentration of disodium edetate (EDTA). The crystalline phase has a great influence on their photovoltaic performance. The photoelectric conversion efficiency increases by 162% when the anatase weight ratio increases from 6% to 51%. While a 263% increase in the photoelectric conversion efficiency of the optimized mixed-phase TiO2 nanorods is achieved when compared to the pure rutile phase TiO2. Accordingly, the DSSCs based on the optimized mixed-phase TiO2 nanorods assembled microspheres show a high open circuit voltage of 0.85 V and a conversion efficiency of 8.85% with a relative low dye adsorption of 0.99 × 10−7 mol cm−2.