Burkholderia pseudomallei RpoS regulates OxyR and the katG-dpsA operon under conditions of oxidative stress

Burkholderia pseudomallei, the causative agent of the potentially fatal tropical disease melioidosis, is known to be highly resistant to oxidative stress although the mechanism of this resistance remains to be fully elucidated. Previous studies have shown that an OxyR is involved in the regulation of oxidative stress via the katG and dpsA genes encoding KatG and DpsA and that the alternative sigma factor, RpoS, plays a critical role in resistance to oxidative stress by regulating katG and katE genes. Here it is shown that RpoS is essential for expression of the oxidative stress regulator OxyR, since a mutant strain lacking RpoS failed to induce oxyR expression both during normal growth and under conditions of oxidative stress. It is further demonstrated that the RpoS acts as a positive transcriptional regulator of oxyR and dpsA expression, while OxyR acts as a negative transcriptional regulator of the katG-dpsA operon via OxyR repressor under normal growth conditions, and as a positive transcriptional regulator via OxyR under conditions of oxidative stress. Therefore both RpoS and OxyR are required to promote expression of both the katG-dpsA operon and dpsA gene.