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Light‐dependent and asynchronous replication of cyanobacterial multi‐copy chromosomes
Author(s) -
Watanabe Satoru,
Ohbayashi Ryudo,
Shiwa Yuh,
Noda Aska,
Kanesaki Yu,
Chibazakura Taku,
Yoshikawa Hirofumi
Publication year - 2012
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2012.07971.x
Subject(s) - biology , origin of replication , dna replication , genetics , gene , chromosome , control of chromosome duplication , dna , genome , circular bacterial chromosome , bacillus subtilis , microbiology and biotechnology , bacteria
Summary 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 . 7942 TK 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 .