A CIRCADIAN RHYTHM IN CELL DIVISION IN A PROKARYOTE, THE CYANOBACTERIUM SYNECHOCOCCUS WH7803

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Authors

  • Beatrice M. Sweeney,

    Corresponding author
    1. Department of Biological Sciences, University of California, Santa Barbara, California 93106
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  • M. Beatriz Borgese

    1. Department of Biological Sciences, University of California, Santa Barbara, California 93106
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    • Museo Argentino de Ciencias Naturales, Avd. Angel Gallardo 470, Basilla de Correozzo 220, Sucursal 5, 1405 Buenos Aires, Rep. Argentina.


  • Received 25 July 1988. Accepted 19 September 1988.

  • This research was supported by Grant No. PCM83 14314 from the National Science Foundation. We are grateful to Prof. Barbara B. Prézelin for supplying us with a culture of Synechococcus strain WH7803.

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ABSTRACT

Circadian rhythms are common in eukaryotes, but the several claimed cases in prokaryotes are all open to alternative interpretation. We report here a clearcut circadian rhythm in cell division in a marine Synechococcus sp. strain WH7803, under conditions where the generation time is longer than one day, that is entrained by a light–dark cycle, and that persists for at least four cycles in continuous light (2 μE·m−2·s−1) and constant temperature (22, 20 or 16°C) with a maximum in dividing cells at about 24 h intervals. Thus, the prokaryote, Synechococcus, satisfies the criteria for the possession of a true temperature-compensated circadian clock. Were the existence of such a rhythm confirmed, current hypotheses that intracellular compartments are required for circadian timing may require modification.

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