Antibacterial Activity of Sirodesmin PL Phytotoxin: Application to the Selection of Phytotoxin-Deficient Mutants.
Sirodesmin PL, a phytotoxin and mycotoxin produced by Leptosphaeria maculans, the causal agent of stem-canker disease of crucifers, exhibited antibacterial activity against gram-positive bacteria and particularly Bacillus subtilis. The importance of the disulfide bridge of the molecule in antibacterial activity was demonstrated. A simple and reliable bioassay based on the antibacterial activity of the toxin was performed for screening sirodesmin PL-deficient mutants when grown on solid culture medium. A mutant was selected and found to produce 3,700-fold less toxin than did the wild-type strain. A sensitive procedure for quantification of the toxin by high-pressure liquid chromatography was developed. Levels of product as low as 100 ng could be detected by this procedure.
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Laboratoire de Cryptogamie, SN , Université des Sciences et Techniques de Lille I, 59655 Villeneuve d'Ascq Cedex, France.