References of "Guez, Jean-Sébastien"
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See detailSecond harmonic generation to monitor the interactions of the antimicrobial mycosubtilin with membrane-mimicking interfacial monolayers
Nasir, Mehmet Nail ULg; Benichou, Emmanuel; Guez, Jean-Sébastien et al

in BioNanoScience (2012), 2(2), 108-112

Mycosubtilin is a strong antimicrobial agent belonging to the iturinic lipopeptide family which contains a single tyrosine residue. Its cell target has been shown to be the cytoplasmic membrane. This ... [more ▼]

Mycosubtilin is a strong antimicrobial agent belonging to the iturinic lipopeptide family which contains a single tyrosine residue. Its cell target has been shown to be the cytoplasmic membrane. This tyrosine residue has been previously shown to be essential for the biological activity of mycosubtilin. Since we have previously demonstrated that tyrosine, an aromatic amino acid, can be used as an endogenous probe for the frequency doubling process, the presence of a tyrosine residue in mycosubtilin allowed us to investigate the interactions of mycosubtilin with biomimetic lipid monolayers at the air–water interface by second harmonic generation (SHG). Mycosubtilin was added underneath dipalmitoylphosphatidylcholine or cholesterol monolayers at the air–water interface and significant increases in the surface pressure were observed in both cases. This observation demonstrates that mycosubtilin interacts with these biomimetic membranes. A light polarization resolved analysis of the SHG signals recovered for these two systems was then performed and confirmed that those interactions between the tyrosine residue in mycosubtilin and the membranes could be monitored by SHG. Furthermore, the differences exhibited by the nonlinear optical measurements for different membranes showed that these interactions depend on the nature of the biomimetic membrane present at the air–water interface. [less ▲]

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See detailCellular engineering of Bacillus subtilis to enhance the biosynthesis of highly active anti fungal lipopeptides
Guy, J.; Guez, Jean-Sébastien; Coucheny, F. et al

Poster (2010)

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See detailHigh-level biosynthesis of the anteiso-C(17) isoform of the antibiotic mycosubtilin in Bacillus subtilis and characterization of its candidacidal activity.
Fickers, Patrick ULg; Guez, Jean-Sebastien; Damblon, Christian ULg et al

in Applied and Environmental Microbiology (2009), 75(13), 4636-40

High-level production (880 mg liter(-1)) and isolation of the anteiso-C(17) isoform of the lipopeptide mycosubtilin produced by a genetically engineered Bacillus subtilis strain are reported. Antifungal ... [more ▼]

High-level production (880 mg liter(-1)) and isolation of the anteiso-C(17) isoform of the lipopeptide mycosubtilin produced by a genetically engineered Bacillus subtilis strain are reported. Antifungal activity of this isoform, as determined via culture and fluorometric and cell leakage assays, suggests its potential therapeutic use as an antifungal agent, in particular against Candida spp. [less ▲]

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See detailTemperature dependence of mycosubtilin homologue production in Bacillus subtilis ATCC6633.
Fickers, Patrick ULg; Leclere, Valerie; Guez, Jean*-Sebastien et al

in Research in Microbiology (2008), 159(6), 449-57

Bacillus subtilis ATCC6633 produces mycosubtilin, a non-ribosomally synthesized lipopeptide of the iturin family which presents antagonistic activities toward various phytopathogens. Different homologues ... [more ▼]

Bacillus subtilis ATCC6633 produces mycosubtilin, a non-ribosomally synthesized lipopeptide of the iturin family which presents antagonistic activities toward various phytopathogens. Different homologues with fatty acid moiety varying from C15 to C17 are usually co-produced, with their biological activities increasing with the number of carbons in the fatty acid chain. In the present report, we highlight that growth temperature modulates both the extent of mycosubtilin production and the relative abundance of the different homologues. A 30-fold increase in mycosubtilin production was observed when the temperature was decreased from 37 degrees C to 25 degrees C for both strain ATCC6633 and its derivative BBG100, a constitutive mycosubtilin overproducer. However, no significant difference in either the expression of the mycosubtilin synthetase encoding genes or in the intracellular synthetase concentration could be found, suggesting that the observed phenotype originated from a higher mycosubtilin synthetase turnover at lower temperature. We also point out that lower growth temperature leads to an increased proportion of odd-numbered fatty acid homologues as a consequence of de novo synthesis of C17 anteiso fatty acid following cell adaptation to low temperatures. [less ▲]

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See detailDirecting the lipopeptide Mycosubtilin biosynthesis toward C17:0 branched isoform influences the expression of cspB and cspC in Bacillus subtilis
Guez, Jean-Sébastien; Drucbert, A.; Müller, C. et al

Poster (2007)

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See detailMycosubtilin overproduction by Bacillus subtilis BBG100 enhances the organism's antagonistic and biocontrol activities
Leclère, Valérie; Béchet, Max; Adam, Akram et al

in Applied and Environmental Microbiology (2005), 71(8), 4577-4584

A Bacillus subtilis derivative was obtained from strain ATCC 6633 by replacement of the native promoter (if he mycosubtilin operon by a constitutive promoter originating from the replication gene repU of ... [more ▼]

A Bacillus subtilis derivative was obtained from strain ATCC 6633 by replacement of the native promoter (if he mycosubtilin operon by a constitutive promoter originating from the replication gene repU of the Staphylococcus aureus plasmid pUB110. The recombinant strain, designated BBG100, produced up to 15-fold more mycosubtilin than the wild type produced. The overproducing phenotype was related to enhancement of the antagonistic activities against several yeasts and pathogenic fungi. Hemolytic activities were also clearly increased in the modified strain. Mass spectrometry analyses of enriched mycosubtilin extracts showed similar patterns of lipopeptides for BBG100 and the wild type. Interestingly, these analyses also revealed a new form of mycosubtilin which was more easily detected in the BBG100 sample. When tested for its biocontrol potential, wild-type strain ATCC 6633 was almost ineffective for reducing a Pythium infection of tomato seedlings. However, treatment of seeds with the BBG100 overproducing strain resulted in a marked increase in the germination rate of seeds. This protective effect afforded by mycosubtilin overproduction was also visualized by the significantly greater fresh weight of emerging seedlings treated with BBG100 compared to controls or seedlings inoculated with the wild-type strain. [less ▲]

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