Role of Burkholderia pseudomallei Sigma N2 in Amino Acids Utilization and in Regulation of Catalase E Expression at the Transcriptional Level.

Burkholderia pseudomallei is the causative agent of melioidosis. The complete genome sequences of this pathogen have been revealed, which explain some pathogenic mechanisms. In various hostile conditions, for example, during nitrogen and amino acid starvation, bacteria can utilize alternative sigma factors such as RpoS and RpoN to modulate genes expression for their adaptation and survival. In this study, we demonstrate that mutagenesis of rpoN2, which lies on chromosome 2 of B. pseudomallei and encodes a homologue of the sigma factor RpoN, did not alter nitrogen and amino acid utilization of the bacterium. However, introduction of B. pseudomallei rpoN2 into E. coli strain deficient for rpoN restored the ability to utilize amino acids. Moreover, comparative partial proteomic analysis of the B. pseudomallei wild type and its rpoN2 isogenic mutant was performed to elucidate its amino acids utilization property which was comparable to its function found in the complementation assay. By contrast, the rpoN2 mutant exhibited decreased katE expression at the transcriptional and translational levels. Our finding indicates that B. pseudomallei RpoN2 is involved in a specific function in the regulation of catalase E expression.