ScienceDaily (Apr. 8, 2010) — A team of researchers at MIT and the University of California at San Diego has shown how cell division in a type of bacteria known as cyanobacteria is controlled by the same kind of circadian rhythms that govern human sleep patterns.
Physics Professor Alexander van Oudenaarden, left, works in his lab with physics graduate student Bernardo Pando. (Credit: Photo by Patrick Gillooly)
The researchers demonstrate, for the first time, how the circadian clock regulates the bacteria's rate of cell division (their method of reproduction) in single cells. "These cells have to keep dividing, and the circadian oscillator regulates when they divide," says Bernardo Pando, an MIT graduate student in physics and one of the lead authors of a paper describing the findings in the March 18 online edition of Science.
In multicellular animals, including humans, cell division is critical for renewal and repair, while out-of-control cell division leads to cancer, so "understanding how cells are dividing is really of fundamental importance," says Susan Golden, professor of molecular biology at the University of California at San Diego and an author of the paper.
Cyanobacteria maintain their circadian rhythms even when isolated from the naturally occurring daily light-dark cycles of the sun, just as humans do. The researchers found that under conditions of moderate constant light, the cyanobacteriaundergo cell division about once per day, and the divisions take place mostly at the midpoint of the 24-hour cycle.
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Vol. 327. no. 5972, pp. 1522 - 1526
DOI: 10.1126/science.1181759
Circadian Gating of the Cell Cycle Revealed in Single Cyanobacterial CellsQiong Yang,1,* Bernardo F. Pando,1,* Guogang Dong,2 Susan S. Golden,2 Alexander van Oudenaarden1,3,
Although major progress has been made in uncovering the machinery that underlies individual biological clocks, much less is known about how multiple clocks coordinate their oscillations. Wesimultaneously tracked cell division events and circadian phases of individual cells of the cyanobacterium Synechococcus elongatus and fit the data to a model to determine when cell cycle progression slows as a function of circadian and cell cycle phases. We infer that cell cycle progression in cyanobacteria slows during a specific circadian interval but is uniform across cell cycle phases. Our model is applicable to the quantification of the coupling between biological oscillators in other organisms.
1 Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
2 Center for Chronobiology and Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA.
3 Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
* These authors contributed equally to this work.
To whom correspondence should be addressed. E-mail: avano@mit.edu
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