A pyocin-like T6SS effector mediates bacterial competition in Yersinia pseudotuberculosis.

Within the realm of Gram-negative bacteria, bacteriocins are secreted almost everywhere, and the most representative are colicin and pyocin, which are secreted by Escherichia coli and Pseudomonas aeruginosa, respectively. Signal peptides at the amino terminus of bacteriocins or ABC transporters can secrete bacteriocins, which then enter bacteria through cell membrane receptors and exert toxicity. In general, the bactericidal spectrum is usually narrow, killing only the kin or closely related species. Our previous research indicates that YPK_0952 is an effector of the third Type VI secretion system (T6SS-3) in Yersinia pseudotuberculosis. Next, we sought to determine its identity and characterize its toxicity. We found that YPK_0952 (a pyocin-like effector) can achieve intra-species and inter-species competitive advantages through both contact-dependent and contact-independent mechanisms mediated by the T6SS-3 while enhancing the intestinal colonization capacity of Y. pseudotuberculosis. We further identified YPK_0952 as a DNase dependent on Mg2+, Ni2+, Mn2+, and Co2+ bivalent metal ions, and the homologous immune protein YPK_0953 can inhibit its activity. In summary, YPK_0952 exerts toxicity by degrading nucleic acids from competing cells, and YPK_0953 prevents self-attack in Y. pseudotuberculosis.IMPORTANCEBacteriocins secreted by Gram-negative bacteria generally enter cells through specific interactions on the cell surface, resulting in a narrow bactericidal spectrum. First, we identified a new pyocin-like effector protein, YPK_0952, in the third Type VI secretion system (T6SS-3) of Yersinia pseudotuberculosis. YPK_0952 is secreted by T6SS-3 and can exert DNase activity through contact-dependent and contact-independent entry into nearby cells of the same and other species (e.g., Escherichia coli) to help Y. pseudotuberculosis to exert a competitive advantage and promote intestinal colonization. This discovery lays the foundation for an in-depth study of the different effector protein types within the T6SS and their complexity in competing interactions. At the same time, this study provides a new development for the toolbox of toxin/immune pairs for studying Gram-negative bacteriocin translocation.

Discovery of Flavone Derivatives Containing Carboxamide Fragments as Novel Antiviral Agents.

Plant virus diseases seriously affect the yield and quality of agricultural products, and their prevention and control are difficult. It is urgent to develop new and efficient antiviral agents. In this work, a series of flavone derivatives containing carboxamide fragments were designed, synthesized, and systematically evaluated for their antiviral activities against tobacco mosaic virus (TMV) on the basis of a structural-diversity-derivation strategy. All the target compounds were characterized by 1H-NMR, 13C-NMR, and HRMS techniques. Most of these derivatives displayed excellent in vivo antiviral activities against TMV, especially 4m (inactivation inhibitory effect, 58%; curative inhibitory effect, 57%; and protection inhibitory effect, 59%), which displayed similar activity to ningnanmycin (inactivation inhibitory effect, 61%; curative inhibitory effect, 57%; and protection inhibitory effect, 58%) at 500 µg mL-1; thus, it emerged as a new lead compound for antiviral research against TMV. Antiviral mechanism research by molecular docking demonstrated that compounds 4m, 5a, and 6b could interact with TMV CP and disturb virus assembly.

K313, a novel benzoxazole derivative, exhibits anti-inflammatory properties via inhibiting GSK3ß activity in LPS-induced RAW264.7 macrophages.

Benzoxazole and its derivatives have been widely studied in recent years due to their various biological properties. A previous study has demonstrated that K313 (1H-indole-2,3-dione 3-(1,3-benzoxazol-2-ylhydrazone)), a novel benzoxazole derivative, inhibits T cell proliferation to yield immunosuppressive effects. However, there are no related reports about its anti-inflammatory effects. In the present study, we investigated the anti-inflammatory properties and the underlying molecular mechanism of K313 in lipopolysaccharide (LPS)-induced RAW264.7 macrophages. K313 dose-dependently (5, 10, and 20 µM) inhibited LPS-stimulated nitric oxide (NO), interleukin (IL)-6, tumor necrosis factor (TNF)-α, and 3-nitrotyrosine (3-NT) production and significantly decreased the gene transcription levels of inducible nitric oxide (iNOS), IL-6, and TNF-α. In addition, the results showed that the inflammatory cytokines suppressed by K313 were not regulated by p65 NF-κB, ERK1/2, AKT, or p38 MAPK. Instead, K313 increased phosphorylation of glycogen synthase kinase-3 beta (GSK-3ß) (Ser9) resulting in GSK-3ß deactivation. Moreover, in LPS-stimulated RAW264.7 macrophages, K313 and lithium chloride (LiCl) had a synergistic effect on the anti-inflammatory response. These results indicated that K313 exhibited anti-inflammatory properties and revealed the potential mechanism. K313 can increase GSK-3ß (Ser9) phosphorylation to decrease GSK-3ß activation in LPS-induced RAW264.7 macrophages.

A prediction model for two-dimensional pressure distribution from underwater shock wave focusing by an ellipsoidal reflector.

Underwater shock wave focusing by ellipsoidal reflector is an important method for medical treatment, detection, and acoustic warfare. However, its pressure field is difficult to predict due to complicated physics. In this study, the pressure by focusing is modeled based on theories of shock wave propagation, nonlinear reflection, and nonlinear focusing, and the calculation domain is determined by approximate equations of wave fronts and lines. The pressure field during the whole process is described by combining direct and focusing pressures in the time and space domains. On this basis, the focusing behavior is simulated, and obtained pressure profiles are compared with experimental results, and the influence of reflector length on focusing performance is also discussed. The results indicate that although there are some rough assumptions, this model can simulate the underwater focusing in some detail and does a good job of predicting the pressure distribution, especially for the positive peak pressure, with an error below 10%; as the reflector length increases, the dynamic focus tends to move linearly forward to the other geometric focus, and the pressure gain increases continuously but the growth rate decreases.