Submitted to: Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/21/2005
Publication Date: 6/21/2005
Citation: Pham, V.D., Shebelut, C.W., Diodati, M.E., Bull, C.T., Singer, M. 2005. Mutations affecting predation ability of the soil bacterium Myxococcus xanthus. Microbiology. 151:1865-1874. Interpretive Summary: Plant pathogens interact with the microbial communities in agricultural ecosystems. The interactions can result in disease suppression or enhancement depending on circumstances that include environmental factors. Our program is investigating the role of myxobacteria in agricultural ecosystems and their role in suppression of plant disease and reduction in plant pathogen populations. Myxobacteria bacteria prey on other microorganisms. Here we demonstrate that factors including development that are regulated by low nutrient availability also regulate predation. This research will help us to understand factors which increase or stimulate predation of plant pathogens. This will ultimately lead to the understanding of how these organisms can be used to increase plant health.
Technical Abstract: Myxococcus xanthus genetic mutants with characterized phenotypes were analyzed for their predation abilities. First, early developmental regulatory mutants were examined, because their likely functions in assessing the local nutrient status was predicted to be also important for predation. The results indicate that predation is most dependent on the very earliest developmental components, such as AsgA, but also that components active during the aggregation phase, like SdeK and CsgA, are still required for predation. On the other hand, later components, such as DevRS, 4406, and PhoP4 do not appear to play significant roles in predation. In addition to developmental mutants, motility genes were also assessed for their involvement in predation. The data show that adventurous (A) motility is required for predation, while social (S) motility is not. Finally, when wild M. xanthus strains were compared to the laboratory-adapted strain DK1622, the data reveal that predation ability is a diverse phenotype. A simple, reproducible, and quantitative method for assaying predation, under conditions in which prey bacteria provide the only source of nutrients, was developed to gather these observations. They were corroborated by data derived using a previously-published protocol that measures predation in the presence of limited external nutrients. The data from these analyses show that patterns of defects in predation on different prey species varies among the genetic mutants tested, suggesting the existence of more than one predation pathway.