ABSTRACTInsect larvae killed by entomopathogenic nematodes are thought to contain bacterial communities dominated by a single bacterial genus, that of the nematode's bacterial symbiont. In this study, we used next-generation sequencing to profile bacterial community dynamics in greater wax moth (Galleria mellonella) larvae cadavers killed byHeterorhabditisnematodes and theirPhotorhabdussymbionts. We found that, althoughPhotorhabdusstrains did initially displace anEnterococcus-dominated community present in uninfectedG. mellonellainsect larvae, the cadaver community was not static. Twelve days postinfection,Photorhabdusshared the cadaver withStenotrophomonasspecies. Consistent with this result,Stenotrophomonasstrains isolated from infected cadavers were resistant toPhotorhabdus-mediated toxicity in solid coculture assays. We isolated and characterized aPhotorhabdus-produced antibiotic fromG. mellonellacadavers, produced it synthetically, and demonstrated that both the natural and synthetic compounds decreasedG. mellonella-associatedEnterococcusgrowth, but notStenotrophomonasgrowth,in vitro. Finally, we showed that theStenotrophomonasstrains described here negatively affectedPhotorhabdusgrowthin vitro. Our results add an important dimension to a broader understanding ofHeterorhabditis-Photorhabdusbiology and also demonstrate that interspecific bacterial competition likely characterizes even a theoretically monoxenic environment, such as aHeterorhabditis-Photorhabdus-parasitized insect cadaver.IMPORTANCEUnderstanding, and eventually manipulating, both human and environmental health depends on a complete accounting of the forces that act on and shape microbial communities. One of these underlying forces is hypothesized to be resource competition. A resource that has received little attention in the general microbiological literature, but likely has ecological and evolutionary importance, is dead/decaying multicellular organisms. Metazoan cadavers, including those of insects, are ephemeral and nutrient-rich environments, where resource competition might shape interspecific macrobiotic and microbiotic interactions. This study is the first to use a next-generation sequencing approach to study the community dynamics of bacteria within a model insect cadaver system: insect larvae parasitized by entomopathogenic nematodes and their bacterial symbionts. By integrating bioinformatic, biochemical, and classicin vitromicrobiological approaches, we have provided mechanistic insight into how antibiotic-mediated bacterial interactions may shape community dynamics within insect cadavers.
Dispersal and Repulsion of Entomopathogenic Nematodes to Prenol
