Versatile roles of rubredoxin reductase of Pseudomonas aeruginosa TBCF10839 in virulence and stress protection

Many microorganisms can degrade alkanes, using them as carbon source. The first and key step in alkane utilization is its hydroxylation, which requires a catalytic membrane-bound monooxygenase, a soluble rubredoxin and a soluble rubredoxin reductase. By comparing the phenotype of Pseudomonas aeruginosa strain TBCF10839 with an isogenic mutant that carries a plasposon within the rubredoxin reductase gene rubB (PA5349) and the complemented mutant, we report multiple, yet unknown roles of rubredoxin reductase in the physiology of P. aeruginosa beyond alkane hydroxylation. The plasposon mutant TBCF10839 rubB::Tn5 was severely compromised in its versatility to degrade protein and did not produce any N-acyl homoserine lactone signal molecules. Consequently, the quorum-sensing deficient mutant was avirulent in the Caenorhabditis elegans fast killing infection model. An intact rubB gene was essential for the TBCF10839 strain to inactivate hydrogen peroxide and to persist and multiply in human neutrophils. Upon exposure to hydrogen peroxide, the ternary complex of rubredoxin reductase, rubredoxin and catalase initially mediates the direct reduction to water followed by disproportionation into water and oxygen when the NADH pool is depleted. In summary, P. aeruginosa TBCF10839 engages the electron-transfer proteins rubredoxin reductase and rubredoxin for stress protection and virulence.