Studies on the microbial interactions involving beneficial insects and entomopathogens

The relationships between different bacteria and beneficial insects (i.e., honeybee and pest predators) and their interactions were investigated to assess their safety and to evaluate their application potential in beekeeping and agroecosystem management. The secretome of food-borne lactic acid bacteria (LAB) and of a honeybee-borneBrevibacillus laterosporusstrain, showed significant inhibitory properties against the honeybee pathogenPaenibacillus larvae. The antagonistic action of LABs was found to be related to the production of organic acids and antimicrobial peptides. Gene expression analyses on highly activeLactobacillus plantarumstrains revealed the activation of plantaricin related genes. LC-MS/MS analyses of a protein precipitate fromB. laterosporusculture supernatant led to the identification of several putative antimicrobials, among which the bacteriocin laterosporulin was found to be the major component. Laboratory bioassays conducted with an entomopathogenic strain of Brevibacillus laterosporus did not cause significant lethal effects on larval instars and adults of the green lacewingChrysoperla agilis. The effects of direct bacterial feeding observed on chrysopid egg hatching, development, fecundity and longevity were not significant. Slight sub-lethal effects were instead detected on lacewing larvae fed withB. laterosporustreated mealworm beetles (tritrophic interaction).