Burkholderia pseudomallei Secretes Metallo- and Serine Proteases in Culture

Burkholderia pseudomallei is a Gram-negative bacterium that causes melioidosis in humans and livestock in Southeast Asia and Northern Australia. Several virulence factors including an extracellular protease have been implicated in the pathogenesis of melioidosis. In the study reported here, our aim was to monitor the optimum length of time for protease production and determine the class of extracellular protease over seven consecutive days of in vitro culture. All the harvested culture filtrates of B. pseudomallei were ammonium sulfate precipitated, dialysed and lyophilized prior to DEAE-Sephacel anion exchange chromatography. The purified protease was characterized using serine, cysteine, aspartate and metalloprotease inhibitors. Protease characterization by SDS-PAGE and zymography identified a protein of 37 kDa. Protease activity was evaluated both in culture filtrates and partially purified protease by azocasein hydrolysis at 405 nm absorbency. Based on the data, we conclude that B. pseudomallei in culture secretes a metallo and a serine protease which could be involved in disease manifestation