Two novel antibiotics, Sch 419558 and Sch 419559, produced by Pseudomonas fluorescens : effect on activity by overexpression of RpoE

Abstract Two new secondary metabolites designated as Sch 419558 ( 1 ) and Sch 419559 ( 2 ), were isolated from the fermentation broth of Pseudomonas fluorescens . Structure elucidation of 1 and 2 was accomplished by spectroscopic data analyses including MS and NMR experiments. Both compounds were identified as lipopeptides containing valine and threonine linked with 1-amino-1-hydroxy-heptadec-9-en-2-one or 1-amino-1-hydroxy-pentadecan-2-one carbon chains, respectively. Characterization of the amino acids was further confirmed by amino acid analysis. Compounds 1 and 2 exhibited antibacterial activity against a sensitized E. coli strain with minimum inhibitory concentration of 0.3 and 0.6 μg/mL, respectively. Overexpression of RpoE in the E. coli strain increased the MIC over 60-fold for compounds 1 and 2 .