Positive Regulation Mechanism in Localizing Cell Division Proteins in Escherichia Coli

Abstract

How cellular components self-organize in space and time is a major open question of cell biology and biophysics. Escherichia coli is capable of localizing its cell division apparatus, the divisome, relative to the center of the cell with remarkable accuracy and robustness [1]. So far, two molecular systems, the Min system and nucleoid occlusion mechanism, have been identified as playing a role in this localization process. Surprisingly, we found that E. coli without the Min and nucleoid occlusion systems was still capable of accurately localizing its divisome with respect to the cell center in slow growth conditions. In this localization process, the initial Z-ring assembly occurs over the center of the nucleoid instead of nucleoid-free regions of the cell. Using live cell fluorescent imaging we determined that divisome components track the Ter macrodomain region of the chromosome within 50 nm accuracy throughout the cell cycle [2]. The Ter macrodomain region thus acts as a landmark for cell division proteins. We furthermore found that the recognition of Ter region by divisome is mediated by MatP, ZapB and ZapA proteins - the Ter linkage. Unlike the Min system and SlmA mediated nucleoid occlusion, the Ter linkage guides initial assembly of the Z-ring through a positive regulatory mechanism.[1] Mannik J, Wu F, Hol FJH, Bissichia P, Sherratt DJ, Keymer JE, Dekker C (2012) Robustness and accuracy of cell division in Escherichia coli in diverse cell shapes. Proc Natl Acad Sci USA 109 (2012) 6957.[2] Bailey MW, Bisicchia P, Warren BT, Sherratt DJ, Mannik J (2014) Evidence for divisome localization mechanisms independent of the Min system and SlmA in Escherichia coli. PLOS Genetics 10 (2014) e1004504.