Abstract

András Fodor*, Andrea M. Fodor, Steven Forst, Joseph S. Hogan, Michael G. Klein, Katalin Lengyel, Gyula Sáringer, Erko Stackebrandt, R. A. J. Taylor and

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 the Steinernema-symbiont Xenorhabdus bacteria may provide options for simultaneous applications in pathogen control. Antibacterial activities of representative strains of Xenorhabdus budapestensis, Xenorhabdus szentirmaii, Xenorhabdus innexi, Xenorhabdus ehlersii, Xenorhabdus nematophila, Xenorhabdus bovienii and Xenorhabdus cabanillassii were 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 AmberliteR 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-Xenorhabdus activity 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 Xenorhabdus species with strong antibacterial activity could be co-cultured and they might be used simultaneously for pathogen control.