Characterizing the role of the Burkholderia cepacia Type Six Secretion System in interbacterial competition

Emily Landolt Biology
Lexie Matte Biology

Elizabeth Danka Assistant Professor of Biology


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Burkholderia cepacia is a gram-negative bacterium that causes onion soft rot and can also act as an opportunistic pathogen, especially in patients who suffer from cystic fibrosis (CF). B. cepacia has been known to outcompete Pseudomonas spp. that cause common infections in CF patients. The Type VI secretion system (T6SS) is one mechanism that bacteria can use for interbacterial competitions. The T6SS secretes toxins across the cell membrane and into the cytoplasm of a neighboring cell. One protein that is critical for T6SS function is VgrG, which forms the tip of the syringe-like structure. We recently identified a B. cepacia strain with a mutated vgrG and have started to characterize the use of this gene. Preliminary interbacterial competition assays between a wild type B. cepacia and a vgrG mutant have shown that the mutant is a less effective competitor, and will be out competed by the wild type. These competition assays were tested at room temperature, 30°C, and 37°C (body temperature in humans). Competitions at 37°C showed the greatest difference in competitive ability where the wild type out competes the vgrG mutant. This suggests that this vgrG and the T6SS genes associated with it are most active at 37˚C, are used for interbacterial competition in a simple in vitro model, and that this system may contribute to interbacterial competition in a human host. In the future, competitions between B. cepacia and a Pseudomonas species can be set up to observe the competitive dynamics between species that cause infections in humans.

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