Effect of a highly concentrated lipopeptide extract of <Emphasis Type="Italic">Bacillus subtilis</Emphasis> on fungal and bacterial cells |
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Authors: | Augusto Etchegaray Carolina de Castro Bueno Itamar Soares de Melo Siu Mui Tsai Marli de Fátima Fiore Maria Estela Silva-Stenico Luiz Alberto Beraldo de Moraes Omar Teschke |
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Institution: | Faculdade de Química, PUC-Campinas, C. Postal 317, Campinas, SP 13012-970, Brazil. augusto.etchegaray@puc-campinas.edu.br |
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Abstract: | Lipopeptides produced by Bacillus subtilis are known for their high antifungal activity. The aim of this paper is to show that at high concentration they can damage
the surface ultra-structure of bacterial cells. A lipopeptide extract containing iturin and surfactin (5 mg mL−1) was prepared after isolation from B. subtilis (strain OG) by solid phase extraction. Analysis by atomic force microscope (AFM) showed that upon evaporation, lipopeptides
form large aggregates (0.1–0.2 μm2) on the substrates silicon and mica. When the same solution is incubated with fungi and bacteria and the system is allowed
to evaporate, dramatic changes are observed on the cells. AFM micrographs show disintegration of the hyphae of Phomopsis phaseoli and the cell walls of Xanthomonas campestris and X. axonopodis. Collapses to fungal and bacterial cells may be a result of formation of pores triggered by micelles and lamellar structures,
which are formed above the critical micelar concentration of lipopeptides. As observed for P.
phaseoli, the process involves binding, solubilization, and formation of novel structures in which cell wall components are solubilized
within lipopeptide vesicles. This is the first report presenting evidences that vesicles of uncharged and negatively charged
lipopeptides can alter the morphology of gram-negative bacteria. |
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Keywords: | Antimicrobial peptides Non-ribosomal peptides Lipopeptides Iturin Surfactin Atomic force microscope Bacillus subtilis Xanthomonas |
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