Supplementary Figure 4: Influence of different concentrations of membrane anchors on FtsZ filament patterns.

(a) Representative snapshots of FtsZ filaments recruited to the membrane by ZipA at indicated time points after addition of GTP. The percentage of Ni²⁺-chelating lipids (18:1 DGS-NTA-Ni²⁺) defines the amount of ZipA immobilized and the amount of FtsZ recruited to the membrane. With 8% Ni²⁺ chelating lipids, FtsZ bundles densely covered the membrane. At lower concentrations (1%, 2% and 4%), bundles of FtsZ filaments start to appear after about 20 min. On membranes with 1% Ni²⁺-chelating lipids, individual FtsZ filaments could briefly be resolved (see 3 min after addition of GTP), before the filament density became too high. Similar micrographs were obtained in 5 experiments. (b) Simplified phase diagram of FtsZ–FtsA filament networks on the membrane. Filled green dots represent experiments with protein concentrations allowing for the formation of a dynamic filament network (at protein concentrations of [FtsZ]>0.7 μM and 0.125 μM<[FtsA]<1.7 μM). Empty dots represent experiments where FtsZ filaments were either too short for a continuous polymer network (with FtsZ<0.7 μM) or where they did not show rapid rearrangements (with FtsA<0.125 μM). Light green area represents the concentration ratio for FtsA and FtsZ found in vivo²⁶. Yellow filled circle represents the concentration ratio used for single FtsZ filament experiments. (c) Representative snapshots and overlays of two individual frames separated by 2 min of a time-lapse movie. At low FtsA concentrations (top), FtsZ forms static, long filaments, whereas at high FtsA concentrations (bottom), filaments were short and dynamic, but did not form a continuous filament network. Similar micrographs were obtained in 5 experiments.