Fig. 1

Secondary mutations restore temperature resistance to ftsZ84 cells without increasing FtsZ concentration. a Location of the FtsZ84 (G105S) point mutation and the three intragenic suppressors of that mutation mapped onto an FtsZ dimer from Staphylococcus aureus. G10S5S (blue) is the original ftsZ84 point mutation. GDP is shown in gray. The three intragenic suppressors F39L, M206I and V293I are highlighted in the inset. The crystal structure is modified from the S. aureus FtsZ dimer structure (PDB ID: 3WGN) [52]. b Plating efficiency assays of wild-type, ftsZ84, and the three intragenic ftsZ84 suppressor strains. Tenfold dilutions of cells cultured in permissive conditions were plated under permissive and nonpermissive conditions. This experiment was repeated 3 times with identical results. One representative experiment is shown. c Growth as measured by absorbance (OD₆₀₀) of wild-type, ftsZ84, and the three intragenic ftsZ84 suppressor strains under nonpermissive conditions. Error bars represent standard deviation of 3 independent experiments. d Quantitative immunoblot indicates that intracellular FtsZ concentrations are wild type in ftsZ84 and ftsZ84* mutants under nonpermissive conditions. After ~3 mass doubling periods in LB no salt, cells were sampled at equivalent OD’s to ensure the same amount of protein was loaded per lane and protein bands were normalized to total protein (Ponceau staining) as a loading and transfer control. ImageJ software was used to quantify band intensity. The average and standard deviation of 3 independent experiments are shown below the blot