Diazotrophy under continuous light in a marine unicellular diazotrophic cyanobacterium, Gloeothece sp. 68DGA, by Y. Taniuchi, S. Yoshikawa, S. Maeda, T. Omata and K. Ohki
Microbiology vol. 154, part 7, pp. 1859 - 1865
Fig. S1. Left: oscillation of nitrogenase activity (acetylene reduction activity) in Gloeothece sp. 68DGA cultured under 12h light/12 h dark cycles (LD). Nitrogenase activity was observed only during the dark phase, with the peak around the middle of the dark phase. Right: immunocytochemical detection of nitrogenase (the Fe-protein) in individual cells grown under LD. Cells were collected at 3 h intervals from an LD-acclimated culture, fixed with paraformaldehyde and preserved in methanol at -30 °C. The fixed and preserved cells were treated with DMSO (for permeabilization) and non-immune rabbit serum (for blocking) and then incubated with an anti-Fe-protein antibody. The immunoreaction was visualized with horseradish peroxidase-conjugated secondary antibody and the chromogenic substrate 3,3'-diaminobenzidine tetrachloride (DAB) in the presence of H2O2. A dark brown deposit of oxidized DAB was observed in nitrogenase-containing cells. The immunostained cells accounted for about 97% of the total cell population in the middle of the dark phase. The proportion of immunostained cells decreased to about 30% during the middle of the light phase, and the staining became faint. [PDF] (572 kb)
Fig. S2. Left: nitrogenase activity (acetylene reduction activity) of Gloeothece sp. 68DGA in cells acclimated to continuous light (CL). Nitrogenase activity was observed constantly at the same level. Right: immunocytochemical detection of nitrogenase (the Fe-protein) in individual cells acclimated to CL. Cells were collected at 4.8 h intervals from a CL-acclimated culture. The conditions for immunodetection of nitrogenase were the same as those in Fig. S1. The dark brown deposit of oxidized DAB was always observed in almost all cells. The mean abundance of the immunostained cells in the CL-acclimated culture was 93.8±5.4% (mean for 72 h during CL). [PDF] (791 kb)
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