Role of the Burkholderia type VI secretion system in induction of multinucleate giant cell formation

Many bacterial virulence determinants are secreted proteins (so-called ’effectors’) that benefit the pathogen by allowing it to subvert or damage the host. In pathogenic Gram-negative bacteria, secreted effectors are translocated across two membranes by one of at least nine different secretion systems. Therefore, protein secretion systems are essential for the virulence of pathogenic bacteria. The type VI secretion system (T6SS) plays an important role in the virulence of a variety of pathogenic Gram-negative bacteria.

We are characterising the effectors that are secreted by the T6SS in pathogenic Burkholderia spp. as this will provide information on the disease causing mechanisms employed by these bacteria and may lead to identification of new targets for development of therapeutic agents (members of this genus are currently very difficult to eradicate due to their high level of intrinsic resistance to antibiotics). In this project we focus on the causative agent of melioidosis, B. pseudomallei, that is endemic to tropical areas, particularly South East-Asia. As part of its intracellular lifestyle, B. pseudomallei has the remarkable property of inducing fusion of the eukaryotic host cell with neighbouring uninfected cells as a means of facilitating cell-to-cell spread. The formation of the resulting multinucleated giant cells (MNGCs) requires a functional T6SS. The purpose of the project is to understand the role of the T6SS in this process, particularly the function of the effectors. As B. pseudomallei is highly pathogenic, we will be employing the related species, B. thailandensis, as a surrogate, as it employs the same T6SS for inducing MNGC formation but lacks the T6SS-independent cytotoxic effectors that enhance the virulence of B. pseudomallei.

Experimental approaches will include a broad range of molecular genetic and biochemical techniques, including DNA cloning, directed mutagenesis, mutant generation, tissue culture, protein overproduction and purification, protein-protein interaction studies, proteomics, protein structure determination.