IPLS Seminar- Dr Saul Ares (Universidad Carlos III de Madrid)

Title: Formation and maintenance of nitrogen fixing cell patterns in filamentous cyanobacteria 

Abstract: In the study of the transition between unicellular and multicellular living forms, cyanobacteria forming one-dimensional filaments are important model organisms. The genus Anabaena has received special interest because under nitrogen-limiting conditions, some cells of the filament differentiate into heterocysts, which lose the possibility to divide but are able to fix environmental nitrogen for the colony. These heterocysts form a quasi-regular pattern in the filament, representing a prototype of patterning and morphogenesis in prokaryotes. Recent years have seen advances in the identification of the molecular mechanism regulating this pattern. We use this data to build a theory on heterocyst pattern formation. We find that it is important to model both genetic regulation and the effects of cell division and filament growth. For the genetic regulation, we explicitly model the dynamics of hetR, patS and hetN expression. Our theory reproduces quantitatively the experimental dynamics of pattern formation and maintenance for wild type and mutants.