The guanidinobutyrase GbuA is essential for the alkylquinolone-regulated pyocyanin production during parasitic growth of Pseudomonas aeruginosa in co-culture with Aeromonas hydrophila.

The opportunistic pathogen Pseudomonas aeruginosa controls the production of virulence factors by quorum sensing (QS). Besides cell density, QS in P. aeruginosa is co-regulated by metabolic influences, especially nutrient limitation. Previously, a co-culture model system was established consisting of P. aeruginosa and the chitinolytic bacterium Aeromonas hydrophila, in which parasitic growth of P. aeruginosa is strictly dependent on the QS-controlled production of pyocyanin in response to nutrient limitation (Jagmann et al., ). In this study, the co-culture was employed to identify novel genes involved in the regulation of pyocyanin production. Via transposon mutagenesis, the gene gbuA encoding a guanidinobutyrase was identified, deletion of which led to a loss of pyocyanin production in co-cultures and to a reduced pyocyanin production in single cultures. Addition of the natural substrate of GbuA to the mutant strain enhanced the negative effect on pyocyanin production in single cultures. The gbuA mutant showed a reduced transcription of the pqsABCDE operon and could be complemented by PqsE overexpression and addition of alkylquinolone signal molecules. The strong effect of gbuA deletion on the QS-controlled pyocyanin production in co-cultures showed the value of this approach for the discovery of novel gene functions linking metabolism and QS in P. aeruginosa.