Abstract

Photorhabdus spp. bacteria are associated with infective juveniles of entomopathogenic nematodes of the Heterorhabditidae family. After entering the host, these bacteria cause septicemia and kill the insect within 48-72 h. The objectives of this study were to isolate and identify the symbiont bacteria of the Heterorhabditis sp. SL0708 entomopathogenic nematode, isolated in Valle del Cauca, Colombia. To this end, we performed genotypic, phenotypic and biochemical tests and assessed its pathogenicity using Galleria mellonella larvae. The Photorhabdus luminescens SL0708 bacterial strain that we isolated from nematode SL0708 had the Gram-negative bacillus morphology characteristic of P. luminescens species; after 72 h of incubation, the bacterial colonies were convex, slimy, shiny and small (1 mm in diameter). Biochemical assays showed that the P. luminescens SL0708 strain had properties similar to those described for Photorhabdus sp. to date. However, P. luminescens SL0708 differed from the other subspecies of P. luminescens by its ability to oxidize arabinose, the microorganism has the necessary enzymes to oxidize and transform the monosaccharide into energy, using it as a carbon source. The phylogenetic tree constructed in this study reveals that Photorhabdus sp. SL0708 strain belongs to the species P. luminescens, establishing a close group of P. luminescens hainanesis. Ultimately, last instar larvae of G. mellonella were susceptible to P. luminescens SL0708, with significant differences between treatments.

Key words:  Colombia, 16S rRNA, phylogeny, infective juveniles, entomopathogenic nematodes, Heterorhabditis sp.