Growth kinetics and pathogenicity of Photorhabdus luminescens subsp. akhurstii SL0708

María Teresa Orozco-Hidalgo,A Sáenz-Aponte,Balkys Quevedo-Hidalgo

doi:10.1186/s41938-019-0172-2

María Teresa Orozco-Hidalgo, A Sáenz-Aponte + Show 1 more

Open Access

https://doi.org/10.1186/s41938-019-0172-2

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Abstract

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.

Highlights

For integrated insect pest management, several investigations have demonstrated that entomopathogenic nematodes (EPNs) use is an effective alternative, because it controls different pest species and it is friendly with humans and the environment (Devi and Dhrubajyoti 2017)
Media was inoculated with 10 ml P. luminescens subsp. akhurstii SL0708 culture, containing bioluminescent colonies corresponding to approximately 108 cells per ml; Erlenmeyer flasks with inoculum were incubated at 28 °C and 150 rpm for 24 h
P. luminescens subsp. akhurstii was cultured in H. indica SL0708 in vitro liquid production media, allowing to establish that the growth phase had a direct relationship with the bioluminescence

Summary

Introduction

For integrated insect pest management, several investigations have demonstrated that entomopathogenic nematodes (EPNs) use is an effective alternative, because it controls different pest species and it is friendly with humans and the environment (Devi and Dhrubajyoti 2017). Of all the nematodes studied for insect biological control, Heterorhabditis is one of the most studied genera for EPNs purposes. In Colombia, Heterorhabditis indica SL0708 was isolated from guadua bamboo soils in Valle del Cauca, demonstrating its high efficacy in the management of various pests in crops of economic importance (San-Blas et al 2019). Given its pest management use, in vitro EPN production has gained importance in recent years; it is necessary to meet the demands of the biological. Its life cycle can be divided into three stages: mutualistic association with the IJ, as insect pathogen, and as food source for the nematode (Devi and Dhrubajyoti 2017)

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