Aspects coopératifs de la régulation des sidérophores – COOPIRON

To be resolved at the scale of individuals, microbial population must be studied under a microscope. However, standard methods don't enable to monitor more than 8 generations because the space becomes filled up with microbes. To circumvent this effect, we propose to set up a laser ablation procedure to free space.

We have already shown that cooperation via siderophore secretion (iron chelator) is achieved through local exchange between adjacent cells.

From an experimental point of view, we are currently able to run the laser ablation procedure to maintain a single cell over 15 generations by automatically ablating one of the two sister cells after each division.

The beginning of the project revealed that the understanding of the interactions is essential to understand the global dynamics of the population. Since, the interactions we have measured are correlated over very short distances, the local geometry of cell-cell contacts matters. hence, we aim at understanding the mechanisms at play during the morphogenesis of microbial colonies.

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In tissues, the activity of cells is coordinated to ensure stable tissue function (homeostasis). In spite of considerable progress in the understanding of cell regulation, the coordination between individual and collective behaviours is often not fully understood. For instance, the homeostasis of iron, which is involved in many cellular processes, has never been simultaneously studied at the individual and collective (tissue or colony) scales. We hereby propose to use the intrinsic fluorescence of a bacterial siderophore in order to characterize the homeostasis of iron at both these scales. In Pseudomonas aeruginosa, the low availability of free iron from the environment triggers the synthesis of large amounts of pyoverdine, a strong iron chelator. Pyoverdine is secreted to the environment wherefrom other cells can recapture it. This project is designed to determine the role of collective regulation in iron uptake by monitoring the fluorescence dynamics of all the colony members. We want to investigate the coupling between the behaviour towards iron of a single cell (production, import, export) and its metabolic cost in the environment of the colony.