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MreB is important for cell shape but not for chromosome segregation of the filamentous cyanobacterium Anabaena sp. PCC 7120

Authors

  • Bin Hu,

    1. State Key Laboratory of Protein and Plant Genetic Engineering, College of Life Sciences, Peking University, Beijing 100871, China.
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    • These authors contributed equally to this work.

  • Guohua Yang,

    1. State Key Laboratory of Protein and Plant Genetic Engineering, College of Life Sciences, Peking University, Beijing 100871, China.
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    • These authors contributed equally to this work.

  • Weixing Zhao,

    1. State Key Laboratory of Protein and Plant Genetic Engineering, College of Life Sciences, Peking University, Beijing 100871, China.
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  • Yingjiao Zhang,

    1. The National Center for Plant Genome Research, Beijing 100101, China.
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  • Jindong Zhao

    Corresponding author
    1. State Key Laboratory of Protein and Plant Genetic Engineering, College of Life Sciences, Peking University, Beijing 100871, China.
      E-mail jzhao@pku.edu.cn; Tel. (+86) 10 6275 6421; Fax (+86) 10 6275 1526.
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E-mail jzhao@pku.edu.cn; Tel. (+86) 10 6275 6421; Fax (+86) 10 6275 1526.

Summary

MreB is a bacterial actin that plays important roles in determination of cell shape and chromosome partitioning in Escherichia coli and Caulobacter crescentus. In this study, the mreB from the filamentous cyanobacterium Anabaena sp. PCC 7120 was inactivated. Although the mreB null mutant showed a drastic change in cell shape, its growth rate, cell division and the filament length were unaltered. Thus, MreB in Anabaena maintains cell shape but is not required for chromosome partitioning. The wild type and the mutant had eight and 10 copies of chromosomes per cell respectively. We demonstrated that DNA content in two daughter cells after cell division in both strains was not always identical. The ratios of DNA content in two daughter cells had a Gaussian distribution with a standard deviation much larger than a value expected if the DNA content in two daughter cells were identical, suggesting that chromosome partitioning is a random process. The multiple copies of chromosomes in cyanobacteria are likely required for chromosome random partitioning in cell division.

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