Fig. 1

a Gel filtration of YFP-MreB after streptactin purification and expression under low salt (100 mM NaCl) or under osmotic stress (expression overnight, addition of 500 mM sorbitol and 1 mM betaine). Molecular standards are shown above the elution peaks. Fraction A2 = void volume, fraction A6 = monomeric YFP-MreB, as shown in the SDS-PAGE inserts (Purification buffer: 100 mM Tris HCl, 300 mM NaCl, 1 mM EDTA, 0.2 mM ATP, 5% Glycerol pH 7.5). b Monomer peaks of YFP-MreB, CFP-Mbl, mCherry-MreBH obtained under osmotic stress conditions (indicated by arrows), as outlined previously. c Sucrose gradient (5–15%) of isolated monomer peaks of YFP-MreB, CFP-Mbl, mCherry-MreBH. Biorad gel-filtration standard was used as a reference. (Marker proteins appearing in lane 1: Myoglobin, 2: Ovalbumin, 4: Gamma-Globulin, 10: Thyroglobulin; YFP-MreB, CFP-Mbl, mCherry-MreB appear in lane 2). d Mass photometric analysis of isolated YFP-MreB, CFP-Mbl, mCherry-MreBH monomers and embedded western blot with specific antibodies against the respective protein (V: void volume, M: isolated monomer peak, S: after dialysis to low salt polymerization buffer)