1,723,997 research outputs found
Benzastatin J, a new demethylated derivative of benzastatin B produced by controlled fermentation of Streptomyces nitrosporeus
No full textFeeding experiments of various derivatives of p-aminobenzamide to benzastatins-producing Streptomyces nitrosporeus were performed to observe whether new biosynthetic analogs of benzastatins were produced. The supplementation of p-aminobenzoic acid to the culture medium of Streptomyces nitrosporeus led to the production of benzastatin J, a new demethylated derivative of benzastatin B, while production of benzastatins A and B increased and benzastatins C-G were not detected.open
Verrulactones D and E with unprecedented skeletons, new inhibitors of Staphylococcus aureus enoyl-ACP reductase, from Penicillium verruculosum F375
No full textopen
The Nitrite Transporter Facilitates Biofilm Formation via Suppression of Nitrite Reductase and Is a New Antibiofilm Target in Pseudomonas aeruginosa
No full textBacterial biofilms play roles in infections and avoidance of host defense mechanisms of medically important pathogens and increase the antibiotic resistance of the bacteria. Nitric oxide (NO) is reported to be involved in both biofilm formation and dispersal, which are conflicting processes. The mechanism by which NO regulates biofilm dispersal is relatively understood, but there are no reports about how NO is involved in biofilm formation. Here, by investigating the mechanism by which complestatin inhibits biofilm formation, we describe a novel mechanism for governing biofilm formation in Escherichia coli and Pseudomonas aeruginosa. Nitrite transporter is required for biofilm formation via regulation of NO levels and subsequent c-di-GMP production. Additionally, the nitrite transporter contributes more to P. aeruginosa virulence than quorum sensing. Thus, this study identifies nitrite transporters as new antibiofilm targets for future practical and therapeutic agent development.Biofilm-forming bacteria, including the Gram-negative Pseudomonas aeruginosa, cause multiple types of chronic infections and are responsible for serious health burdens in humans, animals, and plants. Nitric oxide (NO) has been shown to induce biofilm dispersal via triggering a reduction in cyclic-di-GMP levels in a variety of bacteria. However, how NO, at homeostatic levels, also facilitates biofilm formation is unknown. Here, we found that complestatin, a structural analog of vancomycin isolated from Streptomyces, inhibits P. aeruginosa biofilm formation by upregulating NO production via nitrite reductase (NIR) induction and c-di-GMP degradation via phosphodiesterase (PDE) stimulation. The complestatin protein target was identified as a nitrite transporter from a genome-wide screen using the Keio Escherichia coli knockout library and confirmed using nitrite transporter knockout and overexpression strains. We demonstrated that the nitrite transporter stimulated biofilm formation by controlled NO production via appropriate NIR suppression and subsequent diguanylate cyclase (DGC) activation, not PDE activity, and c-di-GMP production in E. coli and P. aeruginosa. Thus, this study provides a mechanism for NO-mediated biofilm formation, which was previously not understood
Chalcomoracin and Moracin C, New Inhibitors of <i>Staphylococcus aureus</i> Enoyl-Acyl Carrier Protein Reductase from <i>Morus alba</i>
No full textBacterial enoyl-acyl carrier protein (ACP) reductase has been confirmed as a novel target for antibacterial drug development. In the screening of inhibitors of Staphylococcus aureus enoyl-ACP reductase (FabI), we found that a methanol extract of leaves of Morus alba L. potently inhibited S. aureus FabI as well as growth of S. aureus. The active principles were identified as chalcomoracin and moracin C by MS and NMR analysis. Chalcomoracin and moracin C inhibited S. aureus FabI with IC 50 of 5.5 and 83.8 μM, respectively. They also prevented the growth of S. aureus with minimum inhibitory concentration (MIC) of 4 and 32 μg/ mL, respectively. Consistent with their inhibition against FabI and bacterial growth, they prevented [ 14C]- acetate incorporation into fatty acid in S. aureus while didn't affect protein synthesis. In this study, we reported that chalcomoracin and moracin C, potent antibacterial compounds from Morus alba, inhibited FabI and fatty acid synthesis.open
Rh(III)- and Ir(III)-catalyzed direct C-H bond transformations to carbon-heteroatom bonds
No full textThe direct manipulation of C-H bonds is now a powerful tool in chemical synthesis. In achieving the current high standard of research progresses, Rh(III) and Ir(III) complexes played an important role to understand the nature of C-H bond activation. While numerous stoichiometric reactions of hydrocarbons with Rh (III) or Ir(III) complexes were scrutinized, their use in catalytic transformations has been relatively undeveloped until recently. Given their outstanding reactivity in C-H activation, they are highly promising candidates for inducing mild C-H functionalizations. In spite of a short development history, numerous contributions from leading research groups made big strides in highly efficient and selective C-H bond transformations for the C-C and C-heteroatom bond formation. In this report, we specifically focus on the Rh(III)- or Ir(III)-mediated direct C-H functionalizations for the C-heteroatom bond formation that is now a rapidly growing area. This report presents the current status of such catalytic systems including scope of substrates and coupling partners as well as brief mechanistic descriptions. © Springer International Publishing Switzerland 2015133411sciescopu
Atromentin and Leucomelone, the First Inhibitors Specific to Enoyl-ACP Reductase (FabK) of Streptococcus pneumoniae
No full textTwo potent inhibitors of FabK, the enoyl-acyl carrier protein (ACP) reductase of Streptococcus pneumoniae, were isolated from the solid state fermentation of an unidentified fungus F010248. Their structures were identified to be atromentin and leucomelone by various spectral analysis. Atromentin and leucomelone inhibited the FabK with IC50 values of 0.24 and 1.57 μM, respectively, while did not inhibit FabI, the enoyl-ACP reductase of either Escherichia coli or Staphylococcus aureus, even at 200 μM. Atromentin and leucomelone are the first inhibitors specific to the enoyl-ACP reductase (FabK) of Streptococcus pneumoniae.open
Macrolactin S, a New Antibacterial Agent with Fab G-inhibitory Activity from Bacillus sp. AT28
No full textIn the course of screening for FabG inhibitors from microbial sources, a new 24-membered ring lactone named macrolactin S, along with the known compound macrolactin B, has been isolated from the mycelium of liquid fermentation cultures of Bacillus sp. AT28. The structure of macrolactin S was determined on the basis of MS and NMR data. Macrolactin S showed a dose-dependent inhibition of Staphylococcus aureus FabG, not inhibiting S. aureus FabI. Also macrolactin S inhibited the growth of 5. aureus, Bacillus subtilis, and Escherichia coli.open
sj-pdf-1-pic-10.1177_09544062211023527 - Supplemental material for Effect of cutting edge geometry change due to tool wear on hole quality in drilling of carbon fiber reinforced plastics using advanced ceramic coated tools
No full textSupplemental material, sj-pdf-1-pic-10.1177_09544062211023527 for Effect of cutting edge geometry change due to tool wear on hole quality in drilling of carbon fiber reinforced plastics using advanced ceramic coated tools by Mohammad Sayem Bin Abdullah, Dave Kim, Patrick Kwon and Tae-Gon Kim in Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science</p
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