TI - Effect of a glucose impulse on the CcpA regulon in Staphylococcus aureus . AB - Background The catabolite control protein A ( CcpA ) is a member of the LacI/GalR family of transcriptional regulators controlling carbon-metabolism pathways in low-GC Gram-positive bacteria . It functions as a catabolite repressor or activator , allowing the bacteria to utilize the preferred carbon source over secondary carbon sources . This study is the first CcpA -dependent transcriptome and proteome analysis in Staphylococcus aureus , focussing on short-time effects of glucose under stable pH conditions . Results The addition of glucose to exponentially growing S.aureus increased the expression of genes and enzymes of the glycolytic pathway , while genes and proteins of the tricarboxylic acid ( TCA ) cycle , required for the complete oxidation of glucose , were repressed via CcpA . Phosphotransacetylase and acetate kinase , converting acetyl-CoA to acetate with a concomitant subSTRate -level PHOSphorylation , were neither regulated by glucose nor by CcpA . CcpA directly repressed genes involved in utilization of amino acids as secondary carbon sources . Interestingly , the expression of a larger number of genes was found to be affected by ccpA inactivation in the absence of glucose than after glucose addition , suggesting that glucose -independent effects due to CcpA may have a particular impact in S.aureus . In the presence of glucose , CcpA was found to regulate the expression of genes involved in metabolism , but also that of genes coding for virulence determinants . Conclusion This study describes the CcpA regulon of exponentially growing S.aureus cells . As in other bacteria , CcpA of S.aureus seems to control a large regulon that comprises metabolic genes as well as virulence determinants that are affected in their expression by CcpA in a glucose -dependent as well as -independent manner .