Characterization of reutericyclin produced by Lactobacillus reuteri LTH2584.
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Lactobacillus reuteri LTH2584 exhibits antimicrobial activity that can be attributed neither to bacteriocins nor to the production of reuterin or organic acids. We have purified the active compound, named reutericyclin, to homogeneity and characterized its antimicrobial activity. Reutericyclin exhibited a broad inhibitory spectrum including Lactobacillus spp., Bacillus subtilis, B. cereus, Enterococcus faecalis, Staphylococcus aureus, and Listeria innocua. It did not affect the growth of gram-negative bacteria; however, the growth of lipopolysaccharide mutant strains of Escherichia coli was inhibited. Reutericyclin exhibited a bactericidal mode of action against Lactobacillus sanfranciscensis, Staphylococcus aureus, and B. subtilis and triggered the lysis of cells of L. sanfranciscensis in a dose-dependent manner. Germination of spores of B. subtilis was inhibited, but the spores remained unaffected under conditions that do not permit germination. The fatty acid supply of the growth media had a strong effect on reutericyclin production and its distribution between producer cells and the culture supernatant. Reutericyclin was purified from cell extracts and culture supernatant of L. reuteri LTH2584 cultures grown in mMRS by solvent extraction, gel filtration, RP-C(8) chromatography, and anion-exchange chromatography, followed by rechromatography by reversed-phase high-pressure liquid chromatography. Reutericyclin was characterized as a negatively charged, highly hydrophobic molecule with a molecular mass of 349 Da. Structural characterization (A. Holtzel, M. G. Ganzle, G. J. Nicholson, W. P. Hammes, and G. Jung, Angew. Chem. Int. Ed. 39:2766-2768, 2000) revealed that reutericyclin is a novel tetramic acid derivative. The inhibitory activity of culture supernatant of L. reuteri LTH2584 corresponded to that of purified as well as synthetic reutericyclin. (+info)
Analysis of toxic effects of Alternaria toxins on esophagus of mice by light and electron microscopy.
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In this study, the possible toxic effects of Alternariol Methyl Ether (AME) and Tenuazonic Acid (TeA) produced by Alternaria species on esophagus of mice were investigated by using light and electron microscopy techniques. Mice were orally fed daily with AME or TeA for 10 months and at the end of this period, the effects of these chemicals on the esophageal mucosa were determined. By light microscopic examination, moderate and severe dysplasia characterized by loss of polarity, nuclear pleomorphism, and hyperchromasia were observed in TeA-treated animals. Electron-microscopic examination of TeA-treated mucosal epithelial cells revealed pyknosis in some nuclei, granulation and increase in chromatin mass, irregularities in the nuclear contours, vacuolization in nucleoplasms. and marked pleomorphism in the nuclei. In conclusion, our results suggested that TeA has higher toxicity as evidenced by dysplastic transformation. (+info)
Studies on the mode of action of reutericyclin.
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The mode of action of reutericyclin was determined with fluorescent dyes that probed the permeability of the cytoplasmic membrane by large molecules, protons, and potassium. A comparison of reutericyclin activity with those of nisin, nigericin, and valinomycin demonstrated that reutericyclin does not form pores but selectively dissipates the transmembrane proton potential. (+info)
Identification of tenuazonic acid as a novel type of natural photosystem II inhibitor binding in Q(B)-site of Chlamydomonas reinhardtii.
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Tenuazonic acid (TeA) is a natural phytotoxin produced by Alternaria alternata, the causal agent of brown leaf spot disease of Eupatorium adenophorum. Results from chlorophyll fluorescence revealed TeA can block electron flow from Q(A) to Q(B) at photosystem II acceptor side. Based on studies with D1-mutants of Chlamydomonas reinhardtii, the No. 256 amino acid plays a key role in TeA binding to the Q(B)-niche. The results of competitive replacement with [(14)C]atrazine combined with JIP-test and D1-mutant showed that TeA should be considered as a new type of photosystem II inhibitor because it has a different binding behavior within Q(B)-niche from other known photosystem II inhibitors. Bioassay of TeA and its analogues indicated 3-acyl-5-alkyltetramic and even tetramic acid compounds may represent a new structural framework for photosynthetic inhibitors. (+info)
Evaluation of analogs of reutericyclin as prospective candidates for treatment of staphylococcal skin infections.
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