Carboxysome Content of Synechococcus Leopoliensis (Cyanophyta) in Response to Inorganic Carbon1

The carboxysome content of chemostat grown Synechococcus leopoliensis (Racib.) Komarek increases under inorganic carbon limitation. At growth rates of ca. 85%μmax the carboxysome content (±SE) was 0.57 ± 0.09 carboxysomes·cell section−1. Under severe carbon limitation (ca. 13%μmax) this increased to 3.4 · 0.3 carboxysomes·cell section−1. Corresponding to this change is a three order of magnitude decrease in the half‐saturation constant of photosynthesis for dissolved inorganic carbon. Nitrogen and phosphorus limitation had no effect on carboxysome content or the kinetics of photosynthesis with respect to inorganic carbon. These results are discussed in light of the apparent lack of photorespiration in these organisms.