Symbiotic interactions are ubiquitous and have played a pivotal role in the evolution of eukaryotes. The outcomes of symbiosis are diverse and may be influenced by host and symbiont genotypes as well as the surrounding ecosystem. The symbiosis between Burkholderia bacteria and the soil amoeba Dictyostelium discoideum can serve as a tractable model to unravel basic questions concerning symbiotic relationships. Burkholderia symbionts infect amoeba cells and impart conditional costs and benefits to their amoeba hosts. Interestingly, Burkholderia infection appears to increase amoeba susceptibility to secondary bacterial infections. Our goal is to probe the effect of culturing Burkholderia infected amoebas with additional bacterial species. Specifically, we ask how secondary bacterial species influence amoeba fitness and whether Burkholderia infected amoebas are susceptible to coinfections with these secondary bacterial species. To answer these questions, we have analyzed the Burkholderia-Dictyostelium symbiosis system in co-culture with six different bacterial species: Agrobacterium tumefaciens, Rhizobium sp., Pantoea sp., Pseudomonas fluorescens, Pseudomonas aeruginosa, and Serratia sp. We labeled Burkholderia with red fluorescent protein (RFP) and secondary bacteria species with green fluorescent protein (GFP) to observe coinfections though confocal imaging. Additionally, we measured host fitness by counting amoeba spore productivity after co-culture with secondary bacterial species under a variety of conditions. Our observations indicate that the degree of secondary bacterial induction is dependent both on Burkholderia and secondary bacteria identity, with most coinfections occurring with Burkholderia-70 infected lines when grown with P. aeruginosa or Rhizobacterium. Amoeba fitness as measured by spore productivity is influenced by Burkholderia infection, secondary bacterial identity, and by culture condition. This study further defines coinfection induction in this symbiosis system and demonstrates the contextual complexity of symbiotic interactions.
|Commitee:||Fowler, Thomas, Liebl, Faith|
|School:||Southern Illinois University at Edwardsville|
|School Location:||United States -- Illinois|
|Source:||MAI 56/06M(E), Masters Abstracts International|
|Keywords:||Burkholderia, Dictyostelium-burkholderia, Fitness, Host, Infections, Symbiosis|
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