The Making of a Heterocyst in Cyanobacteria Annual Review of Microbiology

Heterocyst differentiation that occurs in some filamentous cyanobacteria, such as Anabaena sp. PCC 7120, provides a unique model for prokaryotic developmental biology. Heterocyst cells are formed in response to combined -nitrogen deprivation and possess a microoxic environment suitable for nitrogen fixation following extensive morphological and physiological reorganization. A filament of Anabaena is a true multicellular organism, as nitrogen and carbon sources are exchanged among different cells and cell types through septal junctions to ensure filament growth. Because heterocysts are terminally differentiated cells and unable to divide, their activity is an altruistic behavior dedicated to providing fixed nitrogen for neighboring vegetative cells. Heterocyst development is also a process of onedimensional pattern formation, as heterocysts are semiregularly intercalated among vegetative cells. Morphogens form gradients along the filament and interact with each other in a fashion that fits well into the Turing model, a mathematical framework to explain biological pattern formation.

Automated summary

Heterocyst differentiation in cyanobacteria like Anabaena provides a unique model for prokaryotic developmental biology. Heterocysts, which are formed in response to nitrogen deprivation, play an altruistic role in providing fixed nitrogen for neighboring cells. The development of heterocysts follows a one-dimensional pattern formation, interacting with morphogens in a manner consistent with the Turing model.