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Journal of Bacteriology, July 2008, p. 5111-5119, Vol. 190, No. 14
0021-9193/08/$08.00+0     doi:10.1128/JB.00310-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Population Heterogeneity in Corynebacterium glutamicum ATCC 13032 Caused by Prophage CGP3{triangledown}

Julia Frunzke,1,{dagger} Marc Bramkamp,2 Jens-Eric Schweitzer,1 and Michael Bott1*

Institut für Biotechnologie 1, Forschungszentrum Jülich, D-52425 Jülich, Germany,1 Institut für Biochemie, Universität zu Köln, 50674 Köln, Germany2

Received 29 February 2008/ Accepted 7 May 2008

The genome of Corynebacterium glutamicum type strain ATCC 13032 (accession number BX927147) contains three prophages, CGP1, CGP2, and CGP3. We recently observed that many genes within the CGP3 prophage region have increased mRNA levels in a dtxR deletion mutant that lacks the master regulator of iron homeostasis (J. Wennerhold and M. Bott, J. Bacteriol. 188:2907-2918, 2006). Here, we provide evidence that this effect is due to the increased induction of the prophage CGP3 in the dtxR mutant, possibly triggered by DNA damage caused by elevated intracellular iron concentrations. Upon induction, the CGP3 prophage region is excised from the genome and forms a circular double-stranded DNA molecule. Using quantitative real-time PCR, an average copy number of about 0.1 per chromosome was determined for circular CGP3 DNA in wild-type C. glutamicum. This copy number increased about 15-fold in the dtxR mutant. In order to visualize the CGP3 DNA within single cells, a derivative of the wild type was constructed that contained an array of tet operators integrated within the CGP3 region and a plasmid-encoded YFP-TetR fusion protein. As expected, one to two fluorescent foci that represented the chromosomally integrated CGP3 prophage were detected in the majority of cells. However, in a small fraction (2 to 4%) of the population, 4 to 10 CGP3 DNA molecules could be observed in a single cell. Interestingly, the presence of many CGP3 copies in a cell often was accompanied by an efflux of chromosomal DNA, indicating the lysis of the corresponding cell. However, evidence for the formation of functional infective CGP3 phage particles could not be obtained.

* Corresponding author. Mailing address: Institut für Biotechnologie 1, Forschungszentrum Jülich, D-52425 Jülich, Germany. Phone: 49 2461 61 3294. Fax: 49 2461 61 2710. E-mail: m.bott{at}fz-juelich.de

{triangledown} Published ahead of print on 16 May 2008.

{dagger} Present address: Institute of Microbiology, ETH Zürich, CH-8093 Zürich, Switzerland.

Journal of Bacteriology, July 2008, p. 5111-5119, Vol. 190, No. 14
0021-9193/08/$08.00+0     doi:10.1128/JB.00310-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





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