Growth kinetics and pathogenicity of Photorhabdus luminescens subsp. akhurstii SL0708

Photorhabdus luminescens subsp. akhurstii SL0708 (Enterobacteriaceae) is a symbiont of the entomopathogenic nematode (EPN), Heterorhabditis indica SL0708 (Nematoda: Rhabditida), used for insect pest biological control. In the present study, P. luminescens subsp. akhurstii SL0708 growth kinetic was evaluated considering growth and metabolic phases (phase I, intermediate phase, phase II), as well as pathogenicity. The study can be useful in determining bacterium feeding times in H. indica SL0708 production in liquid culture media. The logarithmic phase of the growth of bacterium was from 0 to 24 h, with a specific growth velocity of 0.21 h⁻¹; during this phase, bacterium at metabolic phase I was detected. Maximum bioluminescence was registered at 24 h (3.437 luminescence AU). Finally, it was evidenced that the bacterial metabolic phase had an effect on the greater wax moth, Galleria mellonella L., larvae mortality rate. Moreover, biochemical tests were the same for all P. luminescens subsp. akhurstii SL0708 sampling times. This research is particularly relevant, since no reports are available on this bacterium isolate in Colombia. In the future, this will allow massive H. indica SL0708 production, because when pre-incubated with its symbiont, it provides essential nutrients for the EPNs development and reproduction.