Specificity of Association between Paenibacillus spp. and the Entomopathogenic Nematodes, Heterorhabditis spp.

摘要

Endospore-forming bacteria, Paenibacillus spp., have\udrecently been isolated in association with insect pathogenic\udnematodes Heterorhabditis spp. Sporangia adhere\udto nematode infective juveniles (J3) and are carried\udwith them into insects. Paenibacillus proliferates in the\udkilled insect along with Heterorhabditis and its obligate\udbacterial symbiont, Photorhabdus, despite the antibiotic\udproduction of the latter. Nematode infective juveniles\udleave the insect cadaver with Paenibacillus sporangia\udattached. The specificity of the relationship between\udPaenibacillus and Heterorhabditis was investigated.\udSporangia of nematode-associated Paenibacillus adhered\udto infective juveniles (but not other stages) of all Heterorhabditis species tested, and to infective juveniles of vertebrate parasitic Strongylida species, but not to a\udvariety of other soil nematodes tested. Paenibacillus\udspecies that were not isolated from nematodes, but\udwere phylogenetically close to the nematode-associated\udstrains, did not adhere to Heterorhabditis, and they\udwere also sensitive to Photorhabdus antibiotics in vitro,\udwhereas the nematode-associated strains were not.\udUnusual longevity of the sporangium and resistance to\udPhotorhabdus antibiotics may represent specific adaptations\udof the nematode-associated Paenibacillus strains\udto allow them to coexist with and be transported by\udHeterorhabditis. Adaptation to specific Heterorhabditis-\udPhotorhabdus strains is evident among the three nematode-\udassociated Paenibacillus strains (each from a different\udnematode strain). Paenibacillus NEM1a and\udNEM3 each developed best in cadavers with the nematode\udfrom which it was isolated and not at all with the\udnematode associate of the other strain. Differences between\udnematode-associated Paenibacillus strains in\udcross-compatibility with the various Heterorhabditis\udstrains in cadavers could not be explained by differential\udsensitivity to antibiotics produced by the nematodes'\udPhotorhabdus symbionts in vitro.