ANTIBIOTIC-RESISTANCE AND PROTEASE PRODUCTION BY PHOTORHABDUS-LUMINESCENS AND XENORHABDUS-POINARII BACTERIA SYMBIOTIC WITH ENTOMOPATHOGENICNEMATODES - VARIATION AMONG SPECIES AND STRAINS

Bacteria in the genera Photorhabdus and Xenorhabdus are highly pathoge nic to insects and are symbiotically associated with nematodes in the genera Heterorhabditis and Steinernema, respectively. We compared extr acellular protease production and resistance to antibiotics (chloramph enicol, erythromycin, neomycin and tetracycline) for 32 isolates of P. luminescens and 11 isolates of X. poinarii taken from nematodes isola ted from soil in southern New Jersey. P. luminescens produced greater amounts of protease, and was more resistant to erythromycin and less r esistant to neomycin than X. poinarii. No interspecific differences in resistance to chloramphenicol or tetracycline were detected. Variabil ity within species was not related to the site, habitat or soil core f rom which the isolates were obtained, and was not associated with vari ation in the color of the host cadaver for P. luminescens. Resistance to erythromycin was positively correlated with resistance to both neom ycin and tetracycline for P. luminescens, but was negatively correlate d with resistance to neomycin for X. poinarii. Antibiotic resistance p rofiles and extracellular protease production might be useful characte ristics for distinguishing among species and strains of these bacteria , probably have ecological significance with respect to intra- and int erspecific competition within host cadavers, and could have implicatio ns for the utility of these organisms for biological control. (C) 1998 Elsevier Science Ltd. All rights reserved.