Abstract

Insect-nematode-bacterium mutualistic associations provide attractive systems for discovery of inter kingdom signal compounds and antibiotics. A better understanding of the biological meaning of the inter-specific diversity of compounds with antimicrobial activity of theSteinernema-symbiont Xenorhabdus bacteria may provide options for simultaneous applications in pathogen control. Anti-bacterial activities of representative strains ofXenorhabdus budapestensis, Xenorhabdus szentirmaii, Xenorhabdus innexi, Xenorhabdus ehlersii, Xenorhabdus nematophila, Xenorhabdus bovienii and Xenorhabdus cabanillassiiwere tested on non-related (Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus) bacteria and on each other by previously published bioassays. All active compounds were adsorbed by Amberlite^R XAD1180. Chemical and thermal stability of antibacterial factors were determined. Antibiotic factors produced by different Xenorhabdus species against each other differ from those used against other competing bacterial genera. Anti-Xenorhabdusactivity of the cell-free medium and sensitivity of the cells of other Xenorhabdus strains negatively correlated in X. innexi and X. bovienii. Some activity remained unchanged during high pressure and 121°C for 10 min. The first comparative analysis of the intraspecific antibacterial activities of Xenorhabdus species demonstrated that some Xenorhabdusspecies with strong antibacterial activity could be co-cultured and they might be used simultaneously for pathogen control.

Key words: Xenorhabdus, autoclaveable antimicrobials, intra-generic, cross-tolerance