(a) The 0.1 μM FtsA*, showing short straight polymeric structures; (b) 0.5 μM FtsA*, showing mostly arcs and short curved protofilaments. Inset shows × 2.5 magnification of a portion of the image, highlighting some FtsA* arcs (scale bar in inset, 40 nm). (c) The 0.1 μM or (d) 0.5 μM FtsA*+5 μM FtsZ, showing bundling of FtsZ protofilaments (large arrow) and FtsA* arcs (smaller arrows). (e) The 0.5 μM FtsA*+ 5 μM FtsZ*, showing assembly of very large FtsZ protofilament bundles/sheets (arrow). (f,g) The 0.5 μM FtsA+5 μM FtsZ*, showing persistence of FtsZ* bundles in the presence of FtsA minirings. (h) Same as (f,g) except with 2.5 μM FtsZ*. Arrows highlight FtsZ* protofilament bundles. (i) Mock experiment with FtsZ* on monolayers, but no FtsA added, showing an unusually dense area with FtsZ* polymers on the monolayer for comparison. Scale bar, 100 nm.