Regulation of polyhydroxyalkanoate biosynthesis in Pseudomonas putida and Pseudomonas aeruginosa.

Regulation of medium-chain-length polyhydroxyalkanoate biosynthesis in Pseudomonas aeruginosa and Pseudomonas putida was studied conducting PHA accumulation experiments and transcriptional analysis of PHA biosynthesis genes with wild type strains and rpoN-negative mutants. In P. putida PHA accumulation was RpoN-independent, whereas in P. aeruginosa PHA accumulation was RpoN-dependent. Transcriptional analysis applying reverse transcriptase-polymerase chain reaction showed strong induction of phaG, encoding the transacylase, under nitrogen starvation in P. putida KT2440 and the respective rpoN-negative mutant, indicating an RpoN-independent regulation of phaG. No transcription of phaG and no PHA accumulation was detected in the rpoN-negative mutant of P. aeruginosa neither from gluconate nor from octanoate as carbon source. Alginate-overproducing mutant P. aeruginosa FRD1 showed strongly decreased PHA accumulation from gluconate but no difference in phaC1 (encoding the PHA synthase) transcription, indicating that alginate biosynthesis competes with PHA biosynthesis regarding acetyl-CoA as precursor for both biopolymers. Transcription of phaF and phaI-F was nitrogen independent.