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


CONCLUSIONS
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.
Seidl
Kati
K
Institute of Medical Microbiology, University of Zürich, Zürich, Switzerland. katiseidl@gmail.com
Müller
Susanne
S
François
Patrice
P
Kriebitzsch
Carsten
C
Schrenzel
Jacques
J
Engelmann
Susanne
S
Bischoff
Markus
M
Berger-Bächi
Brigitte
B
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D005947:Glucose / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D020543:Proteome / Q000235:genetics / Q000378:metabolism; D012329:RNA, Bacterial / Q000235:genetics; D018085:Regulon; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D013211:Staphylococcus aureus / Q000235:genetics* / Q000378:metabolism
D001426:Bacterial Proteins; D020543:Proteome; D012329:RNA, Bacterial; D012097:Repressor Proteins; C069286:catabolite control proteins, bacteria; D005947:Glucose