Tyrosol blocks E. coli anaerobic biofilm formation via YbfA and FNR to increase antibiotic susceptibility.

Bacteria within mature biofilms are highly resistant to antibiotics than planktonic cells. Oxygen limitation contributes to antibiotic resistance in mature biofilms. Nitric oxide (NO) induces biofilm dispersal; however, low NO levels stimulate biofilm formation, an underexplored process.

Curvularin Isolated From Is an Antagonist of RhlR Quorum Sensing in .

Quorum sensing (QS) is an attractive target for the treatment of multidrug-resistant , against which new antibiotics are urgently needed. Because LasR is at the top of the QS hierarchy controlling Rhl and PQS systems, most QS inhibitors have been targeted to LasR. However, it has recently been reported that in clinical isolates of , LasR is frequently mutated and nonfunctional, and RhlR independently acts to produce virulent factors that maintain toxicity.

Tuberous roots of transgenic sweetpotato overexpressing IbCAD1 have enhanced low-temperature storage phenotypes.

Lignin is associated with cell wall rigidity, water and solute transport, and resistance to diverse stresses in plants. Lignin consists of polymerized monolignols (p-coumaryl, coniferyl, and sinapyl alcohols), which are synthesized by cinnamyl alcohol dehydrogenase (CAD) in the phenylpropanoid pathway. We previously investigated cold-induced IbCAD1 expression by transcriptome profiling of cold-stored tuberous roots of sweetpotato (Ipomoea batatas [L.

Directed evolution of glycosyltransferase for enhanced efficiency of avermectin glucosylation.

Avermectin, produced by Streptomyces avermitilis, is an active compound protective against nematodes, insects, and mites. However, its potential usage is limited by its low aqueous solubility. The uridine diphosphate (UDP)-glycosyltransferase (BLC) from Bacillus licheniformis synthesizes avermectin glycosides with improved water solubility and in vitro antinematodal activity.

The food-grade antimicrobial xanthorrhizol targets the enoyl-ACP reductase (FabI) in Escherichia coli.

Xanthorrhizol, isolated from the Indonesian Java turmeric Curcuma xanthorrhiza, displays broad-spectrum antibacterial activity. We report herein the evidence that mechanism of action of xanthorrhizol may involve FabI, an enoyl-(ACP) reductase, inhibition. The predicted Y156V substitution in the FabI enzyme promoted xanthorrhizol resistance, while the G93V mutation originally known for triclosan resistance was not effective against xanthorrhizol.

The Nitrite Transporter Facilitates Biofilm Formation via Suppression of Nitrite Reductase and Is a New Antibiofilm Target in Pseudomonas aeruginosa.

Biofilm-forming bacteria, including the Gram-negative , 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.

Differential effects of alkyl gallates on quorum sensing in Pseudomonas aeruginosa.

Virulence factors and biofilms constitute attractive targets for the prevention of infections caused by multidrug-resistant bacteria. Among alkyl gallates, propyl gallate (PG) and octyl gallate (OG) are used as food preservatives. Here we found that alkyl gallates differentially affect virulence, biofilm formation, and quorum sensing (QS) in Pseudomonas aeruginosa.

Coralmycin Derivatives with Potent Anti-Gram Negative Activity Produced by the Myxobacteria M23.

Seven new coralmycin derivatives, coralmycins C (), D (), E (), F (), G (), H (), and I (), along with three known compounds, cystobactamids 891-2 (8), 905-2 (9), and 507 (10), were isolated from a large-scale culture of the myxobacteria M23. The structures of these compounds, including their relative stereochemistries, were elucidated by interpretation of their spectroscopic and CD data. The structure-activity relationships of their antibacterial and DNA gyrase inhibitory activities indicated that the -nitrobenzoic acid unit is critical for the inhibition of DNA gyrase and bacterial growth, while the nitro moiety of the -nitrobenzoic acid unit and the isopropyl chain at C-4 could be important for permeability into certain Gram-negative bacteria, including and , and the β-methoxyasparagine moiety could affect cellular uptake into all tested bacteria.

Antibacterial Cyclic Lipopeptide Enamidonins with an Enamide-Linked Acyl Chain from a Streptomyces Species.

Three cyclic lipopeptides, including one known (1) and two new (2 and 3) compounds, that possess the rare enamide linkage group were discovered from Streptomyces sp. KCB14A132, an actinobacterium isolated from a soil sample collected from Jeung Island, Korea. The NMR and MS-based characterization showed that they differed in the amino acid residues in the peptide backbone.

Terrein is an inhibitor of quorum sensing and c-di-GMP in Pseudomonas aeruginosa: a connection between quorum sensing and c-di-GMP.

To address the drug-resistance of bacterial pathogens without imposing a selective survival pressure, virulence and biofilms are highly attractive targets. Here, we show that terrein, which was isolated from Aspergillus terreus, reduced virulence factors (elastase, pyocyanin, and rhamnolipid) and biofilm formation via antagonizing quorum sensing (QS) receptors without affecting Pseudomonas aeruginosa cell growth. Additionally, the effects of terrein on the production of QS signaling molecules and expression of QS-related genes were verified.

Enzymatic synthesis of avermectin B glycosides for the effective prevention of the pine wood nematode Bursaphelenchus xylophilus.

Avermectin produced by Streptomyces avermitilis is an anti-nematodal agent against the pine wood nematode Bursaphelenchus xylophilus. However, its potential usage is limited by its poor water solubility. For this reason, continuous efforts are underway to produce new derivatives that are more water soluble.

Daphnane and Phorbol Diterpenes, Anti-neuroinflammatory Compounds with Nurr1 Activation from the Roots and Stems of Daphne genkwa.

The methanol extract of the roots and stems of Daphne genkwa and its constituents yuanhuacin (1) and genkwanine N were previously reported to have Nurr1 activating effects and neuroprotective effects in an animal model of Parkinson's disease (PD). In this study, four more daphnane-type diterpenes (acutilonine F (2), wikstroemia factor M (3), yuanhuadine (5), and yuanhuatine (6)) and two phorbol-type diterpenes (prostratin Q (4) and 12-O-n-deca-2,4,6-trienoyl-phorbol-(13)-acetate (7)) were isolated as Nurr1 activating compounds from the D. genkwa extract.

Genkwalathins A and B, new lathyrane-type diterpenes from Daphne genkwa.

Screening for new natural anti-neuroinflammatory compounds was performed with the traditional folk medicine Genkwa Flos, which potently inhibited nitric oxide (NO) production by LPS-activated microglial BV-2 cells. Two new lathyrane-type diterpenes, genkwalathins A (1) and B (2), and 14 known daphnane-type diterpenes (3-16) were isolated. The lathyrane-type diterpenes were isolated for the first time from the Thymelaeaceae family in this study.

Genomics-Driven Discovery of Chlorinated Cyclic Hexapeptides Ulleungmycins A and B from a Streptomyces Species.

Analysis of the genome sequence of Streptomyces sp. KCB13F003 showed the presence of a cryptic gene cluster encoding flavin-dependent halogenase and nonribosomal peptide synthetase. Pleiotropic approaches using multiple culture media followed by LC-MS-guided isolation and spectroscopic analysis enabled the identification of two new chlorinated cyclic hexapeptides, ulleungmycins A and B (1 and 2).

Production of Bacterial Quorum Sensing Antagonists, Caffeoyl- and Feruloyl-HSL, by an Artificial Biosynthetic Pathway.

A new series comprising phenylacetyl-homoserine lactones (HSLs), caffeoyl-HSL and feruloyl-HSL, was biologically synthesized using an artificial de novo biosynthetic pathway. We developed an Escherichia coli system containing artificial biosynthetic pathways that yield phenylacetyl-HSLs from simple carbon sources. These artificial biosynthetic pathways contained the LuxI-type synthase gene () in addition to caffeoyl-CoA and feruloyl-CoA biosynthetic genes, respectively.

Madurahydroxylactone, an Inhibitor of FtsZ from sp. AN100570.

FtsZ, a bacterial cell-division protein, is an attractive antibacterial target. In the screening for an inhibitor of FtsZ, madurahydroxylactone () and its related derivatives 2-5 were isolated from sp. AN100570.

Improvement of the pharmacological activity of menthol via enzymatic β-anomer-selective glycosylation.

Menthol has a considerable cooling effect, but the use range of menthol is limited because of its extremely low solubility in water and inherent flavor. (-)-Menthol β-glucoside was determined to be more soluble in water (>27 times) than (-)-menthol α-glucoside; hence, β-anomer-selective glucosylation of menthol is necessary. The in vitro glycosylation of (-)-menthol by uridine diphosphate glycosyltransferase (BLC) from Bacillus licheniformis generated (-)-menthol β-glucoside and new (-)-menthol β-galactoside and (-)-menthol N-acetylglucosamine.

Isolation of Coralmycins A and B, Potent Anti-Gram Negative Compounds from the Myxobacteria Corallococcus coralloides M23.

Two new potent anti-Gram negative compounds, coralmycins A (1) and B (2), were isolated from cultures of the myxobacteria Corallococcus coralloides M23, together with another derivative (3) that was identified as the very recently reported cystobactamid 919-2. Their structures including the relative stereochemistry were elucidated by interpretation of spectroscopic, optical rotation, and CD data. The relative stereochemistry of 3 was revised to "S*R*" by NMR analysis.

A Thoracic Surgical Case Presented at the First Academic Meeting of the Chosun (Korean) Medical Association Held in 1947.

The late Prof. Kyeok Boo Han (1913-2005) was one of the pioneers in the early stages of the establishment of thoracic surgery in Korea. He was in charge of thoracic surgery at Seoul National University Hospital from 1948 to the outbreak of the Korean War in 1950.

Medical Student Examination Questions for Thoracic and Cardiovascular Surgery of Almost 60 Years Ago.

Medical student examination questions of 60 years ago are very rare to find irrespective of medical specialty. Recently, medical student examination questions for thoracic and cardiovascular surgery were found, which were presented between 1957 and 1959 at Seoul National University Medical College. All examination questions were hand-written in six pages by a professor as examiner.

A Record Book of Open Heart Surgical Cases between 1959 and 1982, Hand-Written by a Cardiac Surgeon.

A book of brief records of open heart surgery underwent between 1959 and 1982 at Seoul National University Hospital was recently found. The book was hand-written by the late professor and cardiac surgeon Yung Kyoon Lee (1921-1994). This book contains valuable information about cardiac patients and surgery at the early stages of the establishment of open heart surgery in Korea, and at Seoul National University Hospital.

Generation of New Complestatin Analogues by Heterologous Expression of the Complestatin Biosynthetic Gene Cluster from Streptomyces chartreusis AN1542.

The heterologous expression of the biosynthetic gene cluster (BGC) of natural products enables the production of complex metabolites in a well-characterized host, and facilitates the generation of novel analogues by the manipulation of the genes. However, the BGCs of glycopeptides such as vancomycin, teicoplanin, and complestatin are usually too large to be directly cloned into a single cosmid. Here, we describe the heterologous expression of the complestatin BGC.