In all organisms,regulation of gene expression plays an essential part in acclimation to changes in the environment and the metabolic status of cells.However,little is known about the mechanisms by which nutritional and metabolic signals mediate this control.Nonetheless,it is clear that bacterial and eukaryotic gene expression is modulated by carbon metabolism (Wellen and Thompson,2012;Barar(n)ska et al.,2013),and that DNA replication and/or transcription are adjusted in accordance with the demands of the organism as reflected in the levels of specific metabolites.