When a cyanobacteria filament is deprived of combined nitrogen, some vegetative cells differentiate into heterocysts, Which are terminally differentiated nitrogen-fixing cells.

NtcA presents autoregulation [22, 24, 25] and indirectly activates the key gene that controls cell differentiation and pattern formation: hetR [26—28].

The study of cell differentiation and its underlying mechanisms constitutes one of most intriguing problems in biology.

The approach presented here deals With a simple system, heterocyst formation in cyanobacteria filaments, yet compleX enough to capture the main ingredients of some of the mechanisms for cell differentiation and pattern formation under external driving.

However, in the absence of combined nitrogen (cN), a subset of the vegetative cells differentiate into heterocysts, which are terminally differentiated nitrogen-fixing cells.

A chain lacking both PatS and HetN leads to a lethal phenotype in which all cells differentiate [43].