Carbon Catabolite Repression in Bacillus subtilis : Quantitative Analysis of Repression Exerted by Different Carbon Sources

Abstract

In many bacteria glucose is the preferred carbon source and represses the utilization of secondary substrates. In Bacillus subtilis, this carbon catabolite repression (CCR) is achieved by the global transcription regulator CcpA, whose activity is triggered by the availability of its phosphorylated cofactors, HPr(Ser46-P) and Crh(Ser46-P). Phosphorylation of these proteins is catalyzed by the metabolite-controlled kinase HPrK/P. Recent studies have focused on glucose as a repressing substrate. Here, we show that many carbohydrates cause CCR. The substrates form a hierarchy in their ability to exert repression via the CcpA-mediated CCR pathway. Of the two cofactors, HPr is sufficient for complete CCR. In contrast, Crh cannot substitute for HPr on substrates that cause a strong repression. Determination of the phosphorylation state of HPr in vivo revealed a correlation between the strength of repression and the degree of phosphorylation of HPr at Ser46. Sugars transported by the phosphotransferase system (PTS) cause the strongest repression. However, the phosphorylation state of HPr at its His15 residue and PTS transport activity have no impact on the global CCR mechanism, which is a major difference compared to the mechanism operative in Escherichia coli. Our data suggest that the hierarchy in CCR exerted by the different substrates is exclusively determined by the activity of HPrK/P.

Metabolic Fluxes during Strong Carbon Catabolite Repression by Malate in Bacillus subtilis

“…This differs from the commonly held view that B. subtilis first metabolizes PTS carbohydrates followed by non-PTS carbohydrate and, finally, organic acids (3,5,7,8). Such a preference of gluconeogenic substrates over carbohydrates is also referred to as reverse catabolite repression (2) and found in Pseudomonas aeruginosa (46 -48).…”

“…Consistent with the above hypothesis, glucose and malate were fully co-utilized at a specific rate of growth that was higher than on the individual substrates. These physiological data, in particular the concomitant uptake of glucose and malate, demonstrate that malate does not comply with the previously proposed hierarchy in carbon source utilization for B. subtilis (3,5,7,8).…”

“…This effect is propagated throughout the cell by the pleiotropic transcription factor CcpA (6), whose binding to the target sites for catabolite repression is controlled by the presence of HPr(Ser-P). CcpA imposes a strict hierarchy on carbon source utilization, where carbohydratestransportedviathephosphoenolpyruvate(PEP) 2 -dependent phosphotransferase system (PTS) are catabolized first followed by non-PTS carbohydrates and, last, by organic acids (3,5,7,8).…”

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

“…In the presence of glucose or other rapidly metabolized carbon sources, CcpA is activated by formation of a complex with its co-regulator Hpr that needs to be phosphorylated on residue Ser-46 by its cognate kinase HprKP. The CcpA⅐Hpr-Ser(P)-46 complex has an increased affinity for particular cis-acting sequences, termed catabolite-responsive element (cre) sequences, and thereby represses or enhances gene expression depending on the position of the cre in relation to the operator sequence (3,4). In a number of Gram-positive pathogens such as Bacillus anthracis (5), Clostridium difficile (6), Staphylococcus aureus (7), Staphylococcus epidermidis (8), Streptococcus pneumoniae (9), and Streptococcus pyogenes (10), CcpA is also involved in the regulation of virulence determinants.…”

NanI Sialidase, CcpA, and CodY Work Together To Regulate Epsilon Toxin Production by Clostridium perfringens Type D Strain CN3718

“…CcpA interacts with proteins like phosphorylated HPr, which increases its affinity for certain DNA binding sites and results in repression or activation of gene transcription (20,24). There is accumulating evidence that CcpA can also be involved in the control of virulence gene expression by several Gram-positive pathogens, including C. difficile and S. aureus (25)(26)(27)(28)(29).…”