Phenotypic and biochemical characterisation and pathogenicity assessment on Galleria mellonella L. (Lepidoptera: Pyralidae) of symbionts of the entomopathogenic nematode Heterorhabditis amazonensis Andalo et al., 2006

Abstract

The objective of this study was to describe phenotypically and biochemically the symbiotic bacteria associated with three populations of Heterorhabditis amazonensis Andalo et al., 2006 (isolates: UEL-n 01, UEL-n 07, and UEL-n 08) and evaluate their pathogenicity on Galleria mellonella L. (Lepidoptera: Pyralidae) larvae. Bacteria were isolated by maceration of infective juveniles (IJs) and grown in culture medium (NBTA and MacConkey). The characterization of the bacteria was evaluated by employing motility test and biochemical tests like Gram staining, lipase activity, protease, and lecithinase. The production of antibiotics and bioluminescence was also evaluated. The pathogenicity was evaluated on the last instar larvae of G. mellonella at a concentration of 104 cells/mL. The bacteria from the three entomopathogenic nematodes isolates were positive for all biochemical tests except for lecithinase, and have presented bioluminescence when subjected to ultraviolet light, indicating that they belong to the genus Photorhabdus sp. Both were pathogenic to G. mellonella larvae causing 93.3 to 100.0% mortality.