Fig. 4.

Redox responses of fluorescence of FROG/B in Anabaena 7120. (A) Fluorescence images of Anabaena 7120 strain expressing FROG/B (frog/b) transiently and those of wild-type strains (wt). The images were obtained using a diode 405-nm laser for excitation. The images from 420 to 462 nm for the blue range and those from 500 to 562 nm for the green range were observed. Autofluorescence of Anabaena 7120 cells from 651 to 701 nm was also collected, and merged images from these three images were created. Typical heterocyst (open arrow) and vegetative cell (closed arrow) are shown. (Scale bar, 10 μm.) (B) Emission spectra of vegetative cells and heterocysts measured using a confocal microscope in lambda mode. Blue and green boxes show the observed wavelength range used for the blue and green ranges, respectively. Emission spectra of the vegetative cell of frog/b (closed circle; the cells shown in A, closed arrow), the heterocyst of frog/b (open circle; the cells shown in A, open arrow), the vegetative cell of wt (closed triangle; the cells shown in A, closed arrow), and the heterocyst of wt (open triangle; the cells shown in A, open arrow) are shown. (C) F_G/F_B of the vegetative cells (V) and heterocysts (H) determined under the different conditions. The cyanobacterial cells were incubated under dark conditions (0 μmol photons m⁻² s⁻¹, >12 h) or light conditions (50 μmol photons m⁻² s⁻¹, 2 h), and the images were obtained. F_G/F_B values were calculated from these images. Short bars show the averaged values. (D) F_G/F_B changes of FROG/B under mutual light (50 μmol photons m⁻² s⁻¹)/dark conditions. The light period is indicated by the white rectangle above the graph.