Inactivation of Pseudomonas putida KT2440 pyruvate dehydrogenase relieves catabolite repression and improves the usefulness of this strain as a tool in biotechnology

Pyruvate dehydrogenase (PDH) catalyses the irreversible decarboxylation of pyruvate to acetyl-CoA, which feeds the tricarboxylic acids cycle. We analysed how the lack of PDH affects Pseudomonas putida metabolism. Inactivating PDH generated a strain that can no longer use compounds whose assimilation converges into pyruvate, including sugars and several amino acids. Compounds generating acetyl-CoA supported growth. Interestingly, inactivation of PDH led to loss of the carbon catabolite repression (CCR) effect that inhibits the assimilation of non-preferred compounds when other preferred ones are also present. P. putida can degrade many aromatic compounds, most of which generate acetyl-CoA, and is a useful bacterium for biotransformation and bioremediation processes. However, the genes involved in these metabolic pathways are frequently inhibited by CCR when substrates such as glucose or mixtures of amino acids are also present. Our results show that the PDH-null strain could efficiently degrade aromatic compounds in the presence of other preferred substrates, a condition in which the wild type strain could not mineralise them. Since lack of PDH limits the assimilation of many sugars and amino acids, and relieved CCR, the PDH-null strain could be useful in biotransformation or bioremediation processes that imply growth with mixtures of preferred substrates and aromatic compounds. Overall design: We compared the transcriptome of the bacteriaum Pseudomonas putida KT2440 with that of a mutant derivative in which the aceE gene, coding for a component of the pyruvate dehydrogenase, had been inactivated.