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Journal of Bacteriology, November 2000, p. 6192-6202, Vol. 182, No. 21
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

Gene Expression Analysis of the Streptococcus pneumoniae Competence Regulons by Use of DNA Microarrays

Scott Peterson,1 Robin T. Cline,1 Hervé Tettelin,2 Vasily Sharov,3 and Donald A. Morrison4,*

Department of Functional Genomics,1 Department of Microbial Genomics,2 and Department of Bioinformatics,3 The Institute for Genomic Research, Rockville, Maryland 20850, and Laboratory for Molecular Biology, Department of Biological Sciences, University of Illinois at Chicago, Chicago, Illinois 606074

Received 25 April 2000/Accepted 31 July 2000

Competence for genetic transformation in Streptococcus pneumoniae is coordinated by the competence-stimulating peptide (CSP), which induces a sudden and transient appearance of competence during exponential growth in vitro. Models of this quorum-sensing mechanism have proposed sequential expression of several regulatory genes followed by induction of target genes encoding DNA-processing-pathway proteins. Although many genes required for transformation are known to be expressed only in response to CSP, the relative timing of their expression has not been established. Overlapping expression patterns for the genes cinA and comD (G. Alloing, B. Martin, C. Granadel, and J. P. Claverys, Mol. Microbiol. 29:75-83, 1998) suggest that at least two distinct regulatory mechanisms may underlie the competence cycle. DNA microarrays were used to estimate mRNA levels for all known competence operons during induction of competence by CSP. The known competence regulatory operons, comAB, comCDE, and comX, exhibited a low or zero initial (uninduced) signal, strongly increased expression during the period between 5 and 12 min after CSP addition, and a decrease nearly to original values by 15 min after initiation of exposure to CSP. The remaining competence genes displayed a similar expression pattern, but with an additional delay of approximately 5 min. In a mutant defective in ComX, which may act as an alternate sigma factor to allow expression of the target competence genes, the same regulatory genes were induced, but the other competence genes were not. Finally, examination of the expression of 60 candidate sites not previously associated with competence identified eight additional loci that could be induced by CSP.

* Corresponding author. Mailing address: Laboratory for Molecular Biology, Room 4110 MBR, 900 South Ashland Ave., Chicago, IL 60607. Phone: (312) 996-6839. Fax: (312) 413-2691. E-mail: DAMorris{at}uic.edu.

Journal of Bacteriology, November 2000, p. 6192-6202, Vol. 182, No. 21
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.


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