Bacteria Genomes - BURKHOLDERIA THAILANDENSIS

Burkholderia thailandensis is a nonpathogenic gram-negative bacillus that is closely related to Burkholderia mallei and Burkholderia pseudomallei. B. mallei and B. pseudomallei are serious human health hazards and are potential bio-warfare agents. B pseudomallei is the aetiologic agent of melioidosis (also called Whitmore's disease) and is responsible for disease in both humans and animals. It is endemic to a number of tropical regions, particularly South-East Asia and Northern Australia. B. pseudomallei is especially problematic in North-East Thailand where approximately 20% of community-acquired septicaemias can be attributed to this bacterial pathogen.

Burkholderia thailandensis is a motile rod that is commonly found in stagnant waters, soils, and rice paddies in the central and northeastern areas of Thailand.

B.thailandensis sp. nov., is being studied because it is a Burkholderia pseudomallei-like species (genetically and physiologically similar) but is a non-pathogenic soil saprophyte (lives on decaying organic matter in the soil) and does not cause disease in humans. Resaerchers are investigating the genomic factors resulting in such a dramatic difference between two related species.

Biochemically, these two organisms have similar abilities to metabolize various carbon sources, with the exception of L-arabinose, which only B . thailandensis assimilates. Comparative analysis of the B . pseudomallei and B . thailandensis 16S rRNAs revealed differences in 15 nucleotides, which justified the classification of this new Burkholderia species. The most striking difference between these organisms is their ability to cause acute disease in a Syrian hamster model . An intraperitoneal challenge of <101 CFU (colony forming units) of B . pseudomallei causes mortality in hamsters within 3 to 5 days, in contrast to a dose of >106 CFU (colony forming units) for B . thailandensis.

Research results suggest that divergent evolution of a small set of genes, rather than acquisition or loss of pathogenic islands, is associated with the development of different life styles in these bacteria of similar genomic contents. Further divergence between B. mallei and B. pseudomallei may reflect different adaptive processes of B. mallei and B. pseudomallei fine-tuning into their host environments.

One goal of the research is to identify and develop vaccine candidates to protect against the potential misuse B. mallei and B. pseudomallei as a biological weapon.

References:

http://www.tigr.org/tigr-scripts/CMR2/GenomePage3.spl?database=gbt