Induction and repression of the sty operon in Pseudomonas putida CA-3 during growth on phenylacetic acid under organic and inorganic nutrient-limiting continuous culture conditions

The effects of various nutrient-limiting conditions on expression of the sty operon in Pseudomonas putida CA-3 were investigated. It was observed that limiting concentrations of the carbon source phenylacetic acid, resulted in high levels of phenylacetyl coenzyme A (CoA) ligase activity, this was accompanied also by upper pathway styrene monooxygenase enzyme activity. The introduction of inorganic nutrient limitations, (nitrate, sulfate and phosphate), caused a dramatic reduction in detectable levels of phenylacetyl CoA ligase activity, particularly in the presence of the primary carbon source, succinate. Under these conditions it was no longer possible to detect styrene monooxygenase activity. Reverse transcription PCR analysis of total RNA, isolated under each of the continuous culture conditions examined, revealed that variations in the levels of enzyme activity coincided with altered patterns of corresponding paaK (phenylacetyl CoA ligase) and styA (styrene monooxygenase) gene expression. Transcription of the upper pathway regulatory sensor kinase gene styS was also observed to be growth condition-dependent. These observations suggest that induction/repression of the sty operon in P. putida CA-3, during growth on phenylacetic acid under continuous culture conditions, involves regulatory mechanisms coordinately affecting both the upper and lower pathways and acting at the level of gene transcription.