NudC N udix hydrolase from P seudomonas syringae , but not its counterpart from P seudomonas aeruginosa , is a novel regulator of intracellular redox balance required for growth, motility and biofilm formation

Summary Nudix pyrophosphatases, ubiquitous in all organisms, have not been well studied. Recent implications that some of them may be involved in response to stress and in pathogenesis indicate that they play important biological functions. We have investigated NudC Nudix proteins from the plant pathogen P seudomonas syringae pv. tomato str. DC 3000 and from the human pathogen P seudomonas aeruginosa   PAO 1161. We found that these homologous enzymes are homodimeric and in vitro preferentially hydrolyse NADH . The P . syringae mutant strain deficient in NudC accumulated NADH and displayed significant defects in growth, motility and biofilm formation. The wild type copy of the nudC gene with its cognate promoter delivered in trans into the nudC mutant restored its fitness. However, introduction of the P . syringae   nudC gene under the control of the strong tacp promoter into either P . syringae or P . aeruginosa cells had a toxic effect on both strains. Opposite to P . syringae   NudC , the P . aeruginosa   NudC deficiency as well as its overproduction had no visible impact on cells. Moreover, P . aeruginosa   NudC does not compensate the lack of its counterpart in the P . syringae mutant. These results indicate that NudC from P . syringae , but not from P . aeruginosa is vital for bacteria.