Symbiotic and Nonsymbiotic Bacteria Associated With the Entomo-Pathogenic Nematode, Heterorhabditis spp (Rhabditida: Heterorhabditidae) From South India

Sixteen isolates of bacteria obtained from the entomopathogenic nematode (Heterorhabditis sp.) infected cadavers of Galleria mellonella larvae were identified following phenotypic characterization and molecular analysis of 16S rRNA. Two isolates were identified as the symbiotic bacterium, Photothabdus luminescens, while 14 other isolates were represented by nine species of nonsymbiotic bacteria viz., Stenotrophomonas maltophilia, Alcaligenes aquatilis, Brevundimonas diminuta, Brucella pseudointermedia, Ochrobactrum sp., Brucella pseudogrignonensis, Brucella anthropic, Pseudomonas azatoformans and Pseudomonas lactis. The phylogenetic analysis confirmed the evolutionary relationship between P. luminescens and Pseudomonas spp. The study also found a close relationship among the nonsymbiotic bacteria such as A. aquatilis, B. diminuta, Ochrobactrum sp., and Brucella spp. P. luminescens has been documented for its insecticidal effects against a wide range of insects. The two local isolates obtained in this study may be explored for their biocontrol potential against major pests of the region. Further, the association of nonsymbiotic bacteria with the EPN may be investigated.