Most soil functions such as nitrogen (fixation, nitrification, denitrification) and carbon (e.g., hydrolytic enzyme production) cycling, maintenance of soil structure, plant pathogenicity and iron sequestration are attributable to the documented roles of microbes which can be cultured. Pending the realization of the use of culture-independent methods to assess the functions and phenotypes of community members, the application of cultural methods remains the best available means to assess how individual soil microbes may function in the soil microbial community. Studies were undertaken at Theodore Roosevelt National Park from 2001-2003 to identify the predominant culturable prokaryotic species found in the rhizospheres of the exotic, invasive perennial Euphorbia esula/virgata. The hypothesis was that distinct rhizosphere communities of E. esula/virgata would be associated with root herbivory by the flea beetle Aphthona compared to rhizospheres of E. esula/virgata from stands without insect presence. Pseudomonas syringae, P.cichorii Erwinia chrysanthemii all plant pathogens were associated exclusively with herbivory by Aphthona flea beetles. Conversely, Variovorax and Aquaspirillum spp. were a greater proportion of predominant species from roots without Aphthona present. There were also differences in the occurrence of the root pathogen antagonistic Pantoea agglomerans and Stenotrophomonas maltophilia. The gram-positive bacterial communities differed in the makeup of Bacillus, Paenibacillus, Rhodococcus and Arthrobacter species between Aphthona and no Aphthona. Several of the gram-positive species have been shown to cause biomass reduction of E. esula/virgata in combination with root herbivory by Aphthona spp. Each of these species have traits that could singly or in combination affect the success of restoration with native plants.
