Abstract
The bacterial Min protein system provides a major model system for studying reaction-diffusion processes in biology. Here we present the first in vitro study of the Min system in fully confined three-dimensional chambers that are lithography-defined, lipid-bilayer coated and isolated through pressure valves. We identify three typical dynamical behaviors that occur dependent on the geometrical chamber parameters: pole-to-pole oscillations, spiral rotations, and traveling waves. We establish the geometrical selection rules and show that, surprisingly, Min-protein spiral rotations govern the larger part of the geometrical phase diagram. Confinement as well as an elevated temperature reduce the characteristic wavelength of the Min patterns, although even for confined chambers with a bacterial-level viscosity, the patterns retain a ~5 times larger wavelength than in vivo. Our results provide an essential experimental base for modeling of intracellular Min gradients in bacterial cell division as well as, more generally, for understanding pattern formation in reaction-diffusion systems.
Highlights
The Min protein system determines the localization of the division site in a wide range of bacterial cells (Loose et al, 2011b; Lutkenhaus, 2012; Shih and Zheng, 2013; Rowlett and Margolin, 2015)
When E. coli cells were mutated to form a Y shape, a sequence of oscillation nodes along the cell arms was observed that depended on the relative length of the Y shape arms (Varma et al, 2008). These results show that the Min system can adapt to the cell geometry and modify its dynamical behavior
After the supported lipid membranes (SLB) was formed in the device, as described in the Materials and methods, the chip was connected to a syringe pump containing Min buffer
Summary
The Min protein system determines the localization of the division site in a wide range of bacterial cells (Loose et al, 2011b; Lutkenhaus, 2012; Shih and Zheng, 2013; Rowlett and Margolin, 2015). Though it was commonly assumed that it binds the membrane only in its ATP-bound form (de Boer et al, 1991; Hu and Lutkenhaus, 2001; Lackner et al, 2003), a recent work showed that MinD can bind the membrane in the ADP-bound form (Zheng et al, 2014). Several authors showed that MinE can persist on the membrane after MinD detachment (Loose et al, 2011a; Park et al, 2011) or can even interact with the membrane by itself (Hsieh et al, 2010; Shih et al, 2011; Zheng et al, 2014).
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