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Abstract

Background Antimicrobial compounds released by the entomopathogenic nematode-symbiont bacterium Xenorhabdus budapestensis (EMA) are oligopeptides and the "trump" is fabclavine. They kill antibiotic multi-resistant Escherichia coli, Salmonella; mastitis-isolate Staphylococcus aureus, E. coli and Klebisella pneumoniae; S. aureus MRSA strain; plant-pathogenic Erwinia amylovora; Xanthomonas, Clavibacter, and Pseudomonas strains. Each tested Phytophthora isolate proved also sensitive. Fabclavine was claimed toxic, however, Proteus, some Pseudomonas and Agrobacterium strains are resistant. Our goal is to establish a suitable system for genetic analysis of antimicrobial peptide (AMP)resistance by beneficially using the experimental toolkit of Agrobacterium research. Methods. We tested the anti-Agrobacterium activity of the native cell-free culture media (CFCM) of EMA by agar diffusion assay. EMA_PF2 peptide fraction (of reproducible HPLC and MALDI profile) was then isolated from CFCM of EMA and exerted strong AMP activity on both Gram-negative and positive targets. The sensitive/resistant (S/R) phenotype of Agrobacterium strains of known genotype to EMA_PF2 was determined in liquid culture bio-assays.We tested 1 wild-type (A281) and 3 T-DNA-deleted (AGL1, EHA105, A4T) agropine (L, L,-succinamopine, AGR) catabolizing strains with C58 chromosome and of pTiBo542 plasmid; 5 pTi58-plasmid-cured (HP1836, HP1840, HP1841, HP1842, HP1843) and 1 T-DNA deleted and binary vector harboring (SZL4) nopaline-catabolizing strains of C58 chromosome; and 2 T-DNA deleted octopine-catabolizing (OCT) strains with and without binary vector of Ach5 chromosome (SZL2 and HP 1837, respectively).