  A comprehensive approach to cellular differentiation in cyanobacteria is
developed. To this aim, the process of heterocyst cell formation is studied
under a systems biology point of view. By relying on statistical physics
techniques, we translate the essential ingredients and mechanisms of the
genetic circuit into a set of differential equations that describes the
continuous time evolution of combined nitrogen, PatS, HetR and NtcA
concentrations. The detailed analysis of these equations gives insight into the
single cell dynamics. On the other hand, the inclusion of diffusion and noisy
conditions allows simulating the formation of heterocysts patterns in
cyanobacteria strains. The time evolution of relevant component concentrations
are calculated allowing for a comparison with experiments. Finally, we discuss
the validity and the possible improvements of the model.
