Enright, M.R. and Griffin, C.T.
Specificity of Association between Paenibacillus spp. and the Entomopathogenic Nematodes, Heterorhabditis spp.
Microbial Ecology, 48.
Endospore-forming bacteria, Paenibacillus spp., have
recently been isolated in association with insect pathogenic
nematodes Heterorhabditis spp. Sporangia adhere
to nematode infective juveniles (J3) and are carried
with them into insects. Paenibacillus proliferates in the
killed insect along with Heterorhabditis and its obligate
bacterial symbiont, Photorhabdus, despite the antibiotic
production of the latter. Nematode infective juveniles
leave the insect cadaver with Paenibacillus sporangia
attached. The specificity of the relationship between
Paenibacillus and Heterorhabditis was investigated.
Sporangia of nematode-associated Paenibacillus adhered
to infective juveniles (but not other stages) of all Heterorhabditis species tested, and to infective juveniles of vertebrate parasitic Strongylida species, but not to a
variety of other soil nematodes tested. Paenibacillus
species that were not isolated from nematodes, but
were phylogenetically close to the nematode-associated
strains, did not adhere to Heterorhabditis, and they
were also sensitive to Photorhabdus antibiotics in vitro,
whereas the nematode-associated strains were not.
Unusual longevity of the sporangium and resistance to
Photorhabdus antibiotics may represent specific adaptations
of the nematode-associated Paenibacillus strains
to allow them to coexist with and be transported by
Heterorhabditis. Adaptation to specific Heterorhabditis-
Photorhabdus strains is evident among the three nematode-
associated Paenibacillus strains (each from a different
nematode strain). Paenibacillus NEM1a and
NEM3 each developed best in cadavers with the nematode
from which it was isolated and not at all with the
nematode associate of the other strain. Differences between
nematode-associated Paenibacillus strains in
cross-compatibility with the various Heterorhabditis
strains in cadavers could not be explained by differential
sensitivity to antibiotics produced by the nematodes'
Photorhabdus symbionts in vitro.
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