Single-Cell Biophysics: Measurement, Modulation, and Modeling

Single-Cell Biophysics: Measurement, Modulation, and Modeling

Poster Abstracts

88-POS Board 44 The Modulation of Min and Nucleoid Occlusion Systems in Escherichia Coli Wei-Chen Tsai 1 , Jie-Pan Shen 1 , Yi-Ren Chang 2 , Chia-Fu Chou 1 . 1 Academia Sinica, Taipei, Taiwan, 2 National Taiwan Normal University, Taipei, Taiwan. Spatial control of prokaryotic cell division is solely achieved by directing Z-ring assembly at specified position. In E. coli, Min oscillation, together with nucleoid occlusion (NO), destabilize Z-ring in the regions away from midcell to ensure faithful septation. Min oscillation, driven by MinD-ATPase hydrolysis via MinE activation on the membrane, establishes a time-averaged MinCD gradient to yield a pronounced minimum of MinC’s inhibition on Z-ring at midcell. Because early-division proteins ZipA and ZapA/B, along with FtsZ, assemble into complexes that counter-oscillate with Min system, stable oscillations to suppress Z-ring assembly is expected to allow MinC residing in each polar zone longer than the half-time of FtsZ turnover. Even though Min oscillation has been displayed by synthetic systems, it’s unclear the interplays of Min proteins and compartment geometry are sufficient to bolster oscillation stability in vivo. Here the Min-nucleoid interaction is reported as the physicochemical element missing in previous researches to commit stable Min oscillation in vivo. We found, compared with unperturbed cells, Min oscillation in anucleate and nucleoid-perturbed cells was deviated up to a quarter-cycle, but the frequency was higher in anucleate and lower in nucleoid-perturbed cells. Enhanced stability and lowered frequency were observed in cells expressing excess NO factor SlmA. Further, cell filamentation by excess SlmA and associated DNA-binding sites was antagonized by overproduced Min proteins, and as such asymmetric septation was enabled to reduce cell size. Our results reveal an unanticipated role of the nucleoid in the modulation of frequency and stability of Min system; moreover, SlmA is indicated to facilitate such modulations, potentially via directly interacting with Min system. we propose a fresh perspective that frequency modulation of Min system is mediated via the act of nucleoid-associated factor; and envision a model of Min-nucleoid interaction.

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