The effects or changing environmental conditions on expression of the pdh operon were studied in strains containing pyruvate dehydrogenase (PDH) complexes having either one or three lipoyl domains per lipoate acetyltransferase chain. The expression of the pdh operon was lowered during growth on reduced carbon sources and when the mode of energy generation was changed from aerobic respiration to anaerobic respiration and fermentation. In contrast, growth at non-optimal pH increased expression. Operon expression was generally higher in the 1 lip strain compared to the 3 lip strain. Expression of the pdh operon was shown to be tightly controlled in response to environmental stimuli, consistent with its importance in defining metabolic flux.
Cassey, B., Guest, J. R., & Attwood, M. M. (1998). Environmental control of pyruvate dehydrogenase complex expression in Escherichia coli. FEMS Microbiology Letters, 159(2), 325–329. https://doi.org/10.1016/S0378-1097(97)00587-9