Role of Burkholderia pseudomallei rpoS in regulation of catalase activities under hydrogen peroxide induction

Abstract

Burkholderia pseudomallei is the causative agent of melioidosis. A previous study showed that the B. pseudomallei rpoS mutant is more sensitive to hydrogen peroxide than is the wild type strain, suggesting the RpoS may play a critical role in resistance to oxidative stress. Analysis of rpoS gene expression by β-galactosidase activity assay indicated that rpoS is activated when exposed to hydrogen peroxide on entry into the stationary phase. In addition, native gel electrophoresis and staining for catalase activities revealed that there are two types of catalases (I and II) in B. pseudomallei. Catalase I in the rpoS mutant exhibited higher activity than the parent strain, whereas catalase II was not detected in the rpoS mutant strain. Interestingly, even though catalase II was the prominent activity in the stationary phase culture of the wild type, it did not increase in response to hydrogen peroxide treatment. Construction of the B. pseudomallei katE mutant indicated that the katE gene encodes catalase II. Our experiments showed that katE is directly controlled by the RpoS and is not induced by hydrogen peroxide. These results suggest that the B. pseudomallei RpoS is activated under an oxidative stress condition and controls the activities of both catalases, I and II, in different manners.