Indian Journal of Nematology

Xenorhabdus - the bacterial symbiont of the entomopathogenic nematodes of the family Steinernematidae, is a member of the family Enterobacteriaceae, available for use in biological control of broad pest range of various crops as it possess extreme virulence for insect pests. In this study, we undertook the biochemical characterization of 4 native strains of Xenorhabdus on the basis of isozymic profile of Esterase, Superoxide dismutase and Malate dehydrogenase. The Isozymic patterns of esterase of 4 isolates of Xenorhabdus spp. by mini slab gel polyacrylamide electrophoresis, revealed species-specific enzyme phenotypes for all the four strains ie. Xenorhabdus indica, IARI-Xeno-mg1, IARI-Xeno-kr and IARI-Xeno-as1, characterized by having four, five, four and two species- specific bands, respectively. Superoxide dismutase profiles also showed species-specific phenotypes for Xenorhabdus indica and other three strains of Xenorhabdus. In contrast, Malate dehydrogenase profiles revealed species-specific phenotypes for only Xenorhabdus indica and IARI-Xeno-as1 with four bands for each, at Rf 0.42, 0.59, 0.68, 0.91 and at Rf 0.19, 0.42, 0.59, 0.70 respectively. Phenotypes of IARI-Xeno-mg1 and IARI-Xeno-kr remained identical with one band at Rf 0.71. The combination of esterase, superoxide dismutase and malate dehydrogenase isozymic profiles from Xenorhabdus strains were found useful for preliminary differentiation of Xenorhabdus species, which is perhaps, the first report on utility of isozymic profiles as diagnostic markers in the genus Xenorhabdus.