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Journal of Bacteriology, February 2001, p. 915-920, Vol. 183, No. 3
Institute of Biology/Genetics,
Humboldt-University, D-10115 Berlin, Germany,1
and Station Biologique, CNRS, INSU, and Université Pierre
et Marie Curie, F-29682 Roscoff Cedex,2 and
Laboratoire de Physique et Chimie Marines, ESA 7077, CNRS,
INSU, and Université Pierre et Marie Curie,
Villefranche,3 France
Received 14 August 2000/Accepted 7 November 2000
The cell cycle of the chlorophyll b-possessing marine
cyanobacterium Prochlorococcus is highly synchronized under
natural conditions. To understand the underlying molecular mechanisms we cloned and sequenced dnaA and ftsZ, two key
cell cycle-associated genes, and studied their expression. An axenic
culture of Prochlorococcus sp. strain PCC 9511 was grown in
a turbidostat with a 12 h-12 h light-dark cycle for 2 weeks. During
the light periods, a dynamic light regimen was used in order to
simulate the natural conditions found in the upper layers of the
world's oceans. This treatment resulted in strong cell cycle
synchronization that was monitored by flow
cytometry. The steady-state mRNA levels of dnaA and
ftsZ were monitored at 4-h intervals during four
consecutive division cycles. Both genes exhibited clear diel expression
patterns with mRNA maxima during the replication (S) phase. Western
blot experiments indicated that the peak of FtsZ concentration occurred
at night, i.e., at the time of cell division. Thus, the transcript
accumulation of genes involved in replication and division is
coordinated in Prochlorococcus sp. strain PCC 9511 and
might be crucial for determining the timing of DNA replication and cell division.
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.3.915-920.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Diel Expression of Cell Cycle-Related Genes in
Synchronized Cultures of Prochlorococcus sp. Strain
PCC 9511
*
Corresponding author. Mailing address:
Humboldt-University Berlin, Inst. of Biology/Genetics, Chausseestr.
117, D-10115 Berlin, Germany. Phone: 49-30-2093-8144. Fax:
49-30-2093-8139. E-mail: Wolfgang-Hess{at}rz.hu-berlin.de.
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