Light-dependent and asynchronous replication of cyanobacterial multi-copy chromosomes
Article first published online: 18 JAN 2012
© 2012 Blackwell Publishing Ltd
Volume 83, Issue 4, pages 856–865, February 2012
How to Cite
Watanabe, S., Ohbayashi, R., Shiwa, Y., Noda, A., Kanesaki, Y., Chibazakura, T. and Yoshikawa, H. (2012), Light-dependent and asynchronous replication of cyanobacterial multi-copy chromosomes. Molecular Microbiology, 83: 856–865. doi: 10.1111/j.1365-2958.2012.07971.x
- Issue published online: 2 FEB 2012
- Article first published online: 18 JAN 2012
- Accepted manuscript online: 10 JAN 2012 05:51AM EST
- Accepted 31 December, 2011.
While bacteria such as Escherichia coli and Bacillus subtilis harbour a single circular chromosome, some freshwater cyanobacteria have multiple chromosomes per cell. The detailed mechanism(s) of cyanobacterial replication remains unclear. To elucidate the replication origin (ori), form and synchrony of the multi-copy genome in freshwater cyanobacteria Synechococcus elongatus PCC 7942 we constructed strain S. 7942TK that can incorporate 5-bromo-2'-deoxyuridine (BrdU) into genomic DNA and analysed its de novo DNA synthesis. The uptake of BrdU was blocked under dark and resumed after transfer of the culture to light conditions. Mapping analysis of nascent DNA fragments using a next-generation sequencer indicated that replication starts bidirectionally from a single ori, which locates in the upstream region of the dnaN gene. Quantitative analysis of BrdU-labelled DNA and whole-genome sequence analysis indicated that the peak timing of replication precedes that of cell division and that replication is initiated asynchronously not only among cell populations but also among the multi-copy chromosomes. Our findings suggest that replication initiation is regulated less stringently in S. 7942 than in E. coli and B. subtilis.