We are interested in cell signaling with an emphasis on the cellular differentiation in bacteria. Our model is the filamentous cyanobacterium Anabaena PCC 7120. When combined nitrogen becomes limiting, nitrogen-fixing cells called heterocysts differentiate from vegetative cells at semi-regular intervals along the filaments (every 10 to 15 vegetative cells). In the heterocysts, the photosynthesis turns off allowing the oxygen-sensitive nitrogenase to function. Anabaena is thus a prokaryotic model to study both cell differentiation and developmental pattern formation. These developmental processes are spatio-temporally regulated.
Using genetics, cellular biology, and more recently single-cell based approaches, we aim to address major developmental questions of differentiation in Anabaena : What governs the establishment and the persistence on the differentiation pattern ? What discriminates a future-heterocyst cell from its neighbors ? What dictates the “differentiation timing” ?
Besides this developmental project, we are also interested in engineering Anabaena in order to conciliate the oxygen-sensitive hydrogen production with photosynthesis. Since, Sunlight, CO2 and water are the only prerequisite to cyanobacteria growth, these organisms are candidate of choice for the production of biofuels.
Figure 1 : Vegetative growth
Anabaena grows in multicellular filaments. Here, the FtsZ-ring that assembles during vegetative cell division is visualized
Figure 2 : Cell differentiation follows a pattern
When fixed nitrogen becomes limiting, differentiate cells referred as heterocysts (green) are formed every 10 to 15 vegetative cells (red).
Figure 3 : Cell differentiation is temporally regulated
The development of a vegetative cell into a pro-heterocyst and into a mature heterocyst is shown.