The Bacterial Carbon-Fixing Organelle Is Formed by Shell Envelopment of Preassembled Cargo
(A) RbcL-roGFP1 excited with 410nm (left) and 488nm (middle) produces ratiometric (488nm/410nm) differences in emission (right). Scale bar: 1µm. (B) A histogram of this ratio measured at each carboxysome focus reveals an asymmetric distribution biased toward a relatively oxidized state. (C–F) Montages of RbcL-roGFP1 show transitions from predominantly 488nm excitation (green) to 410nm excitation (magenta) over the maturation period of carboxysomes. Carboxysomes establish an oxidizing state before the appearance of a new carboxysome, rarely reopening to the cytosol after an initial closure (G). Arrows indicate birth events. Scale bar: 1µm. Interval: 20 minutes.