FUNCTIONAL CHARACTERIZATION OF ESSENTIAL BURKHOLDERIA PSEUDOMALLEI VIRULENCE REGULATORS

Abstract

Burkholderia pseudomallei (Bp) is a Gram-negative facultative intracellular pathogen that causes the disease melioidosis. Bp is endemic to tropical and subtropical regions around the globe with an expanding reach due to increased awareness and better diagnostics. Melioidosis is predicted to infect 165,000 people and cause 89,000 deaths annually marking this disease as a significant threat to public health. The CDC has classified Bp as a Tier 1 select agent due to potential malicious use and there is currently no licensed vaccine to protect against infection. Bp has one of the most complex bacterial genomes with ~7.24 mega base-pairs of genetic material across two highly plastic chromosomes. The genetic determinants encoded on the Bp genome allow for growth in various environments including many cell types within the human body. Bp has a complex intracellular lifecycle that starts by attaching to host cells, followed by invasion of the cytoplasm and replication within, and finally protrusion towards neighboring cells to continue the spread of infection. Approximately 1,953 genes are differentially regulated in a stage-specific manner indicating that a sophisticated regulation system is in place to coordinate intracellular infection. In order for Bp to sustain a productive infection, it relies on tight control and coordination of virulence factors and metabolic pathways by transcriptional regulators in a stage specific manner. The following dissertation investigates this hypothesis by characterizing three yet to be described transcriptional regulators: i) BP1026B_II1198; ii) BP1026B_II1561; and iii) BP1026B_II2312. Mutants of these transcriptional regulators are attenuated in cell culture and BALB/c mouse models of infection indicating a role during Bp pathogenesis. To characterize these transcriptional regulators I have: i) elucidated the regulation networks using an RNA-seq strategy; ii) determined the direct DNA binding sequences to discover the genes directly controlled by each transcriptional regulator with a ChIP-seq approach; and iii) determined what genes within each regulon contribute to pathogenesis. In addition to the characterization of three novel transcriptional regulators, two potential vaccine candidates were tested showing significant promise towards the development of a protective melioidosis vaccine.