PRODUCTION OF SYRINGOTOXIN AND OTHER BIOACTIVE PEPTIDES BY PSEUDOMONAS-FUSCOVAGINAE

The application of a cell-free extract from a broth culture of Pseudom onas fuscovaginae to rice plants produced leaf sheath necrosis and inh ibited panicle emergence typical of bacterial sheath rot. The extract was also fungistatic to Geotrichum candidum and displayed amphipathic properties. The toxic activity was associated with peptidic substances of less than 5000 Da, migrating in a single broad band on SDS-PAGE. T he toxins were precipitated by desoxycholate/trichloroacetic acid and reverse-phase HPLC of the precipitate showed the presence of five pept idic compounds (A, B, C, D and E), as well as two others (fuscopeptins A and B) which were nor characterized in this study. Using FAB-MS, th e MH(+) ions of the peptides: A to E were 1108, 1102, 1118, 1136 and 1 152, respectively. The most abundant peptide, D, was characterized by amino acid analysis, fatty acid methyl ester analysis and FAB-MS of th e by-products from mild alkaline hydrolysis. The chemical structure of D was identical to syringotoxin (C48H82O18N11Cl), a phytotoxin produc ed by P. syringae pv. syringae Moreover, HPLC analysis of this compoun d indicated that compound D had the same retention time as the syringo toxin standard obtained from citrus strains of P. syringae pv. syringa e. (C) 1996 Academic Press Limited.