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Download date: 12 May 2018Journal of Bioenergetics and Biomembranes, Vol. 27, No. 5, 1995 Received May 29, 1995 Paracoccus denitrificans is a facultative anaerobic bacterium that has the capacity to adjust its metabolic infrastructure, quantitatively and/or qualitatively, to the prevailing growth condition. In this bacterium the relative activity of distinct catabolic pathways is subject to a hierarchical control. In the presence of oxygen the aerobic respiration, the most efficient way of electron transfer-linked phosphorylation, has priority. At high oxygen tensions P. denitrificans synthesizes an oxidase with a relatively low affinity for oxygen, whereas under oxygen limitation a high-affinity oxidase appears specifically induced. During anaerobiosis, the pathways with lower free energy-transducing efficiency are induced. In the presence of nitrate, the expression of a number of dehydrogenases ensures the continuation of oxidative pbosphorylation via denitrification. After identification of the structural components that are involved in both the aerobic and the anaerobic respiratory networks of P. denitrificans, the intriguing next challenge is to get insight in its regulation. Two transcription regulators have recently been demonstrated to be involved in the expression of a number of aerobic and/or anaerobic respiratory complexes in P. denitrificans. Understanding of the regulation machinery is beginning to emerge and promises much excitement in discovery.KEY WORDS: Respiratory network; multiple oxidases; denitrification; gene regulation; FNR; Paracoccus denitrificans; Escherichia coli.
~TRODUCTIONThe ultimate goal of living organisms is to contribute to a continued existence of their species by means of survival and reproduction. In unicellular organisms, the ability to survive depends on the cell's potential to adapt its metabolism to the available carbon and free-energy sources in its natural habitat, ensuring maintenance and growth. The more such an environment is subject to fluctuations in the supply of these substrates, the higher the demands that are made upon the potential of the cell to adjust its metabolic properties. A profound example of this flexibility is the process of bacterial respiration...
