Figure 5.

Redox-dependent regulation of the cell cycle. (A) Ratios (405/488 nm) of roGFP2 during the cell cycle in a synchronized population of wild-type C. crescentus expressing rogfp2 from the chromosomal xylX locus (xylX::P_xyl-rogfp2). The cells were treated with 0.3% xylose to induce the production of roGFP2. The data are an average of eight independent experiments ±SE. (B) Immunoblots of nonreducing SDS-PAGE of NstA-GFP in synchronized populations of cells at 0 and 60 min after synchronization. nstA-gfp was expressed from the xylX locus (xylX::P_xyl-nstA-gfp). (C) Immunoblots of NEM and MP modifications of synchronized samples of the xylX::P_xyl-nstA-gfp collected at 0 and 60 min after synchronization. The samples were treated as described in Figure 4G. The increased-molecular-weight form (NstA-GFP-MP) in the cells at 60 min denotes the existence of disulfide bridges while the cytoplasm is in an oxidized state during cell cycle. No disulfide bridge was formed in the reduced cytoplasm at 0 min, leading to the absence of higher-molecular-weight forms of NstA-GFP. (D) Growth of wild-type (WT) and ΔnstA cells in the presence of the oxidizing agent H₂O₂. Sixfold diluted cultures were spotted onto medium containing 40 µM H₂O₂. (A–C) (Red) Reduced cytoplasm; (green) oxidized cytoplasm. Bar, 2 μm.