Regulation of Fatty Acids Degradation in Bacteria
Fatty acids occupy a central role in bacterial metabolism; they serve as an energy reservoir, as integral components of the membrane, and as signal molecules. As such, their biosynthesis and degradation pathways are tightly regulated. This regulation is controlled directly; for example, in the presence of free fatty acids, the global FadR regulator derepresses genes that encode fatty acid transport and degradation proteins. Fatty acid pathways are also regulated indirectly. This is because Fad genes respond in an integrated manner to different environmental cues. In Escherichia coli, expression of the Fad genes is modulated by (i) the carbon source, mediated by the catabolic repression protein CRP; (ii) oxygen levels, mediated through the ArcA/ArcB two-component system; (iii) osmotic stress, mediated by the EnvZ-OmpR system; and (iv) the physiological status of the cell, mediated by RpoS and ppGpp through direct and indirect mechanisms. In addition to this transcriptional regulation, the glyoxylate shunt is also regulated at the protein level by the phosphorylation of the isocitrate dehydrogenase. This complex network of regulation emphasizes the importance of maintaining the appropriate types and levels of fatty acids according to physiological and environmental conditions and the relevance of fatty acid modulation during the stress response.
This work was funded by Abengoa Research.
We thank Ben Pakuts for editing the manuscript.
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