Starvation acclimation in Cyanobacteria

Prof. Dr. K. Forchhammer

When non-diazotrophic cyanobacteria are deprived for combined nitrogen, they bleach, a process, which is known as chlorosis. We could show that chlorotic cells of the strain Synechococcus PCC 7942 stay alive for many months and are able to regenerate rapidly upon the re-addition of a nitrogen source. We want to understand the molecular mechanisms of this remarkable ability to survive conditions of extreme starvation. How do the cells sense the onset of starvation, and how do they respond to this stressful condition? Several regulatory proteins are involved in survival of chlorosis, among which the NblR protein is of particular importance.
In the long-term, these cells dramatically reduce the amount of soluble intracellular protein and they conserve energy by carrying out a residual photosynthesis amounting to approx. 0,1 % activity of PSI and PSII, as compared to growing cells. The knowledge of the capacities of cyanobacteria to withstand adverse environmental conditions is fundamental to the understanding of the appearance of cyanobacteria in nature, where they play a dominant ecological role.

Additional Information:
Review Article (Acclimation of unicellular cyanobacteria to macronutrient deficiency)
Nitrogen starvation-induced chlorosis in Synechococcus PCC 7942