Regulation of polyhydroxyalkanoate synthases (phaC1 and phaC2) gene expression in Pseudomonas corrugata

In this study we examined polyhydroxyalkanoate (PHA) synthases phaC1 and phaC2 gene expression in two strains of Pseudomonas corrugata (Pc) grown in a minimum mineral medium with related (oleic acid and octanoate) or unrelated (glucose) carbon sources. Analysis of transcription was performed by Northern blot and conventional reverse transcriptase (RT) polymerase chain reaction (PCR). In addition, we developed a RT-real-time PCR method to quantitatively evaluate phaC1(Pc) and phaC2(Pc) gene expression. Primers and a TaqMan probe were designed for the specific detection of both synthase transcripts as well as of the housekeeping 16S rRNA, and the relative expression of target genes was calculated. We showed that phaC1(Pc) and phaC2(Pc) were not cotranscribed and, on the contrary, were independently regulated. In cultures grown with oleic acid as the sole carbon source, only the expression of phaC1(Pc) was induced (a tenfold increase after 72 h of culture), whereas that of phaC2(Pc) remained unchanged. In cultures grown with glucose or sodium octanoate, the expression of both phaC1(Pc) and phaC2(Pc) was upregulated but at different rates. Cellular PHA content was compared to the gene expression of the PHA synthases and significant correlations were found between PHA production and phaC1(Pc)/phaC2(Pc) expression.