that extracellular secondary metabolites were released into the culture broth by Photorhabdus bacteria (i.e., 1,3-dihydroxy-2-[isopropyl]-5-[2-phenylethenyl] benzene, benzylideneacetone, proline-tyrosine, acetylated phenylalanine-glycine-valine indole, oxindole, cis- cyclo-PY, and p-hydroxyphenyl propionic acid)