Entomopathogenic potential of bacteria associated with soil-borne nematodes and insect immune responses to their infection

Abstract

Soil-borne nematodes establish close associations with several bacterial species. Whether they confer benefits to their hosts has been investigated in only a few nematode-bacteria systems. Their ecological function, therefore, remains poorly understood. In this study, we isolated several bacterial species from rhabditid nematodes, molecularly identified them, evaluated their entomopathogenic potential onGalleria mellonellalarvae, and measured immune responses ofG.mellonellalarvae to their infection. Bacteria were isolated fromAcrobeloidessp.,A.bodenheimeri,Heterorhabditis bacteriophora,Oscheius tipulae, andPristionchus maupasinematodes. They were identified asAcinetobactersp.,Alcaligenessp.,Bacillus cereus,Enterobactersp.,Kaistiasp.,Lysinibacillus fusiformis,Morganella morganiisubsp.morganii,Klebsiella quasipneumoniaesubsp.quasipneumoniae, andPseudomonas aeruginosa. All bacterial strains were found to be highly entomopathogenic as they killed at least 53.33%G.mellonellalarvae within 72h post-infection, at a dose of 106CFU/larvae. Among them,Lysinibacillus fusiformis,Enterobactersp.,Acinetobactersp., andK.quasipneumoniaesubsp.quasipneumoniaewere the most entomopathogenic bacteria. Insects strongly responded to bacterial infection. However, their responses were apparently little effective to counteract bacterial infection. Our study, therefore, shows that bacteria associated with soil-borne nematodes have entomopathogenic capacities. From an applied perspective, our study motivates more research to determine the potential of these bacterial strains as biocontrol agents in environmentally friendly and sustainable agriculture.