Multistability and dynamic transitions of intracellular Min protein patterns

Abstract

Cells owe their internal organization to self‐organized protein patterns, which originate and adapt to growth and external stimuli via a process that is as complex as it is little understood. Here, we study the emergence, stability, and state transitions of multistable Min protein oscillation patterns in live Escherichia coli bacteria during growth up to defined large dimensions. De novo formation of patterns from homogenous starting conditions is observed and studied both experimentally and in simulations. A new theoretical approach is developed for probing pattern stability under perturbations. Quantitative experiments and simulations show that, once established, Min oscillations tolerate a large degree of intracellular heterogeneity, allowing distinctly different patterns to persist in different cells with the same geometry. Min patterns maintain their axes for hours in experiments, despite imperfections, expansion, and changes in cell shape during continuous cell growth. Transitions between multistable Min patterns are found to be rare events induced by strong intracellular perturbations. The instances of multistability studied here are the combined outcome of boundary growth and strongly nonlinear kinetics, which are characteristic of the reaction–diffusion patterns that pervade biology at many scales.

Mapping out Min protein patterns in fully confined fluidic chambers

“…Note that in vitro we report the MinE signal while in vivo we imaged MinD (as the MinE signal was low in this strain). Essentially this does not alter the conclusion that is drawn here since in this strain the MinE signal merely follows the MinD signal (see [Wu et al, 2016]).…”

“…Strain FW1919 (W3110 [minDE :: exobrs-sfGFP-minD minE-mKate2 :: frt]) (Wu et al, 2016) was used in order to view Min oscillations in vivo . Cells were inoculated into LB and were grown overnight at 37°C with 250 rpm shaking.…”

“…( a – d ) Four examples of in vivo MinD oscillations in cells with various length of strain FW1919 (see Wu et al, 2016) Mol Sys Biol 12: 873). Panels show montages of the corresponding supporting Supplementary file 2.…”

Geometric cues stabilise long-axis polarisation of PAR protein patterns inC. elegans

“…In particular, it was predicted 23,24 that delayed reattachment to the cell membrane (e.g., due to cytosolic nucleotide exchange) is key to geometry sensing. Indeed, recent experimental studies support the idea that axis selection depends on the interplay between reaction kinetics and cellular geometry 25 . 4 These results suggest that the protein dynamics in the cytoplasm of the C. elegans embryo may also influence the selection of the long over the short axis during polarity maintenance.…”

“…To answer these questions we draw on previous studies of other intracellular pattern-forming protein systems which revealed that even the typically rather fast cytosolic diffusion does not eliminate protein gradients in the cytosol [23][24][25][26] . As a consequence, protein patterns are generically sensitive to cell geometry through coupling between processes in the cytosol and on the membrane.…”