Effect of a glucose impulse on the CcpA regulon in Staphylococcus aureus

Abstract

BackgroundThe 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.ResultsThe 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.ConclusionThis 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.

A Novel Mode of Regulation of the Staphylococcus aureus Catabolite Control Protein A (CcpA) Mediated by Stk1 Protein Phosphorylation

“…42) but not in bacilli (43,44) highlight that some fundamental differences in the regulation of CcpA activity between staphylococci and bacilli exist. Moreover, in combination with our recent observations that CcpA also seems to regulate the expression of some of its target genes in the absence of glucose (13) and that CcpA can readily bind to its cre sequences in absence of its coregulator Hpr-Ser(P)-46 ( Fig. 4 and Ref.…”

“…To test this hypothesis, we analyzed the binding capacities of the nonphosphorylated CcpA form (CcpA) and that of the hyperphosphorylated CcpA form (CcpA-P) to a couple of gene promoter elements that were recently shown to be affected by this regulatory protein (Fig. 4C) (7,(12)(13)(14). Although the unphosphorylated CcpA interacted with all the double-stranded DNA probes tested in our electrophoretic mobility shift assays (Fig.…”

“…In S. aureus, which is one of the leading causes for nosocomial infections and an important human pathogen responsible for a wide variety of diseases, including soft tissue infections, toxic shock syndrome, and necrotizing pneumonia (11), CcpA was shown to affect antibiotic resistance, biofilm formation, expression of toxins such as hla (encoding ␣-hemolysin) and tst (encoding toxic shock syndrome toxin), and infectivity of this bacterium (7,(12)(13)(14)(15). Recent transcriptome and proteome analyses confirmed the broad effects of CcpA on gene expression in S. aureus and suggested this LacI/GalR type of regulator to be active in the presence and absence of glucose (13).…”

“…Recent transcriptome and proteome analyses confirmed the broad effects of CcpA on gene expression in S. aureus and suggested this LacI/GalR type of regulator to be active in the presence and absence of glucose (13). However, the regulatory mechanism(s) that modulates the DNA binding properties of the S. aureus CcpA in the absence of glucose has not yet been identified.…”

Library Screen Identifies Enterococcus faecalis CcpA, the Catabolite Control Protein A, as an Effector of Ace, a Collagen Adhesion Protein Linked to Virulence

“…and the ilv-leu operon for amino acid biosynthesis (24), suggesting the involvement of CcpA in anabolism as well. Moreover, in S. aureus, a large amount of CcpA-dependent gene regulation occurs in the absence of glucose, suggesting a glucose-independent CcpA regulatory mechanism (25).…”