Endosymbionts of entomopathogenic nematodes from south Italy: A phenotypic study

We examined different Xenorhabdus strains (five of X. bovienii and two of X. kozodoii), obtained from EPN isolates belonging to the genus Steinernema (S. feltiae, S. ichnusae, S. apuliae, S. vulcanicum) of different geographic origin by both genotypic and phenotypic analysis. Common laboratory assays were done for traits such as antibiotic resistance, haemolytic activity, lactose utilisation, biofilm production, chosen as the least selectable traits for EPN life-cycle, and thus as (presumably) neutral traits. As selective marker, the activity of the endosymbiont’s toxins was verified in an in vivo assay on G. mellonella larvae. Genotyping done by 16S partial sequencing was used for identification purposes. Xenorhabdus bovienii isolates showed a broad phenotypic spectrum; on the other hand, X. kozodoii showed a less degree of phenotypic variation, reduced ability of biofilm production and conspicuous ?-galactosidase activity. However, all the strains were able to kill G. mellonella larvae with high efficiency.