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Series GSE12614

Query DataSets for GSE12614

Status

Public on Dec 20, 2008

Title

Analysis of the CcpA regulon in Staphylococcus aureus

Platform organism

Staphylococcus aureus

Sample organism

Staphylococcus aureus subsp. aureus str. Newman

Experiment type

Expression profiling by array

Summary

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 S. aureus wild type and ccpA-deleted mutant, focussing on short-time effects of glucose under stable pH conditions.

Results
The addition of glucose to exponentially growing S. aureus increased enzymes of glycolytic pathway, indicating a higher glycolytic activity, while proteins required for the complete oxidation in the TCA cycle were repressed via CcpA.
Phosphotransacetylase and acetate kinase, converting acetylCoA to acetate with a concomitant substrate-level phosphorylation were neither regulated by glucose nor by CcpA. Most CcpA directly repressed genes were involved in utilization of amino acids as secondary carbon sources. More genes were found to be differentially expressed by CcpA in a glucose-independent manner than in the classical, glucose dependent way, suggesting that glucose-independent regulation by CcpA may be of
particular importance in S. aureus. In the presence of glucose, CcpA was
found to regulate expression of genes involved in metabolism, but that
of genes coding for virulence determinants.

Conclusions
This study identified the CcpA regulon of exponentially growing S. aureus, for the first time. As in other bacteria, the CcpA-regulon of S. aureus comprised a large amount of metabolic genes but also some 50 genes associated with virulence. CcpA seemed to work in a glucose- as well as glucose-independent way.

Overall design

The transcriptomes of strain Newman and its isogenic ccpA-deleted mutant were determined in early exponential growth and 30 min after the addition of 10 mM glucose, under controlled pH conditions. In the absence of glucose, the wild type grew slightly faster than the mutant, reaching an OD600 of 1 approximately 20 min earlier than the mutant.
Adding 10 mM glucose at OD600 1 increased the growth rate of the wild type but had only a minor effect on that of the mutant. 60 min after glucose addition, glucose was depleted down to 0.3 mM by the wild type, while still 3 mM glucose was left in the culture of the mutant. Despite increased glucose consumption rates in the wild type, acetate production was only slightly enhanced compared to the mutant. No lactate was excreted at any time point sampled. Acidification of the medium upon glucose metabolism was prevented by buffering, maintaining a pH of
7.5 for both strains and under both growth conditions for at least 2 h after glucose addition, allowing to rule out any pH effects.

Contributor(s)

Seidl K, Muller S, Francois P, Schrenzel J, Engelmann S, Bischoff M, Berger-Bachi B

Citation(s)

19450265

Submission date

Aug 29, 2008

Last update date

Mar 20, 2012

Contact name

FRANCOIS Patrice

E-mail(s)

[email protected]