T6SS effector and immunity pairs: Contributions to Burkholderia cepacia virulence

Lexie Matte Biology (Biomedical Sciences)

Elizabeth Danka Assistant Professor of Biology


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Burkholderia cepacia is a gram-negative bacterium responsible for causing soft rot disease in onions and is an infectious agent in immunocompromised people (particularly those with cystic fibrosis). This bacterium is naturally antibiotic-resistant, so it is important to understand the virulence factors that contribute to the pathogenicity of this organism. Previous work used transposon mutagenesis, a plant model of infection, and bioinformatics to identify a vgrG gene as a virulence factor in B. cepacia ATCC 25416. This gene encodes the vgrG tip protein of the Type Six Secretion System (T6SS), a complex structure found in many species of bacteria. This syringe-like system allows a bacterium to inject toxic proteins into neighboring cells during interbacterial competition or during infection of eukaryotic hosts. In other organisms, a toxic effector protein is attached to the vgrG tip protein and is delivered into a neighboring cell, killing it. The effector protein works as a pair with an immunity protein, which is responsible for preventing the autotoxicity of the bacterium by the effector. We are currently working to characterize effector and immunity genes within the genome that may interact with our vgrG of interest. Currently, we have isolated all individual effector and immunity genes for expression studies in Escherichia coli, a bacterium lacking these pairs. Future experiments will elucidate the activities of the proteins encoded by these effector and immunity genes. The characterization of these pairs is crucial in understanding how the T6SS contributes to the virulence of B. cepacia.

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