A role for the regulator PsrA in the polyhydroxyalkanoate metabolism of Pseudomonas putida KT2440.

Pseudomonas putida KT2440 is a Gram-negative bacterium capable of producing medium-chain-length-polyhydroxyalkanoates (mcl-PHA). When fatty acids are used as growth and polymer precursors, the biosynthesis is linked to fatty acid metabolism via ß-oxidation route. In the close-related Pseudomonas aeruginosa, the transcriptional repressor PsrA regulates the ß-oxidation, but little is known about the regulatory system in P. putida. To analyze the effect of the absence of psrA gene on the growth and PHA production in P. putida, a set of different carbon sources were assayed in the wild type strain and in a generated psrA deficient strain (KT40P). The growth rates were in all cases, lower for the mutant. The amount of PHA produced by the mutant strain is lower than the wild type. Moreover, the monomeric composition seems to be different among the strains, as there is enrichment in monomers with shorter carbon length in the mutant strain. To understand the role of the psrA gene on the metabolism of fatty acids, we have determined the expression profile of several genes related to fatty acid metabolism in the wild type and in the mutant strain. The results indicated that PsrA mostly negatively regulate genes related to fatty acid metabolism.