Figure 2.
FtsZL169R cells survive without the normally essential ZipA. (A) Spot dilutions of indicated strains in WT (W3110) or zipA1 ts backgrounds at 30º or 42ºC. Mid- exponential phase cultures of strains without plasmids were plated on plain LB plates and those with plasmids were plated on LB plates with chloramphenicol and 0.1 μM sodium salicylate to induce expression of ftsZ derivatives. Note that pKG110 includes an unorthodox ribosome-binding site, leading to relatively modest overexpression, while pKG116 has a strong ribosome binding site, leading to high overexpression. (B) Spot dilutions of indicated strains in WT backgrounds or successfully transduced with zipA::kan. Plasmids induced with sodium salicylate as in (A) (C) Representative IFM images of indicated strains. Cells in the zipA1(ts) background were imaged during mid-exponential growth, ~60 minutes following shift to the nonpermissive temperature of 42ºC. Cells permitting bypass of zipA (zipA::kan) were grown at 37ºC and sampled as normal during mid-exponential growth. Signals and scale as in Figure 1A; plasmids induced with sodium salicylate as in (A).