Burkholderia Sequencing Project
Burkholderia pseudomallei is a prevalent environmental organism in tropical areas of the world, particularly in Southeast Asia and Northern Australia. In endemic areas it causes a severe human disease, melioidosis, posing a public health challenge. Melioidosis brings with it high mortality, diagnostic and therapeutic challenges, and the failure of long term efforts to develop an effective vaccine. B. pseudomallei exhibits extensive genome variability including functional prophage in islands of laterally transferred genes. These components of genome variability may contribute to the variability of disease phenotypes in infected patients. B. pseudomallei is listed as a CDC category B select agent.
We have sequenced phenotypically characterized strains of B. pseudomallei that differ in geographic origin. We also have sequenced multiple bacteriophage genomes isolated from various geographic and clinical sources of B. pseudomallei. A striking feature of the B. pseudomallei K96243 genome sequence (http://www.sanger.ac.uk/) is the presence of 16 genomic islands, some of which appear to be prophages, and together made up 6.1% of the genome. It is unclear from the sequence analysis alone whether any of these prophages are capable of lysogeny although one of the putative prophage sequences was shown to be a productive bacteriophage (termed fK96243). The islands have been shown to be variably present in a collection of invasive and soil isolates but are entirely absent from the clonally related organism Burkholderia mallei.
Temperate bacteriophages are responsible for much of the laterally transferred DNA in bacteria and they play a major role in the evolution of bacterial pathogens by providing new virulence determinants. In addition, prophages are a major source of strain-specific differences in several pathogenic bacteria. Variable horizontal gene acquisition by B. pseudomallei is an important feature of recent genetic evolution, and has resulted in a genetically diverse bacterial species. The goal of this project is to identify the specific nucleotide sequences and/or single nucleotide polymorphisms that are correlated with expression of virulence and disease via comparative genomic analysis between B. pseudomallei strains as well as between various bacteriophages harbored within B. pseudomallei. A repository of well-characterized strains will be made publicly available for further studies. This work increases our knowledge of the virulence of this understudied pathogen and provides a foundation for the development of diagnostic and therapeutic countermeasures, as well as a protective vaccine for melioidosis.
Funding
National Institute of Allergy and Infectious Disease (NIAID)