Evidence for Divisome Localization Mechanisms Independent of the Min System and SlmA in Escherichia coli
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Authors: | Matthew W Bailey Paola Bisicchia Boyd T Warren David J Sherratt Jaan M?nnik |
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Institution: | 1.Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee, United States of America;2.Department of Biochemistry, University of Oxford, Oxford, United Kingdom;3.Department of Microbiology, University of Tennessee, Knoxville, Tennessee, United States of America;4.Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee, United States of America;University of Geneva Medical School, Switzerland |
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Abstract: | Cell division in Escherichia coli starts with assembly of FtsZ protofilaments into a ring-like structure, the Z-ring. Positioning of the Z-ring at midcell is thought to be coordinated by two regulatory systems, nucleoid occlusion and the Min system. In E. coli, nucleoid occlusion is mediated by the SlmA proteins. Here, we address the question of whether there are additional positioning systems that are capable of localizing the E. coli divisome with respect to the cell center. Using quantitative fluorescence imaging we show that slow growing cells lacking functional Min and SlmA nucleoid occlusion systems continue to divide preferentially at midcell. We find that the initial Z-ring assembly occurs over the center of the nucleoid instead of nucleoid-free regions under these conditions. We determine that Z-ring formation begins shortly after the arrival of the Ter macrodomain at the nucleoid center. Removal of either the MatP, ZapB, or ZapA proteins significantly affects the accuracy and precision of Z-ring positioning relative to the nucleoid center in these cells in accordance with the idea that these proteins link the Ter macrodomain and the Z-ring. Interestingly, even in the absence of Min, SlmA, and the putative Ter macrodomain – Z-ring link, there remains a weak midcell positioning bias for the Z-ring. Our work demonstrates that additional Z-ring localization systems are present in E. coli than are known currently. In particular, we identify that the Ter macrodomain acts as a landmark for the Z-ring in the presence of MatP, ZapB and ZapA proteins. |
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