Dormant Cells (Akinetes) of Filamentous Cyanobacteria Demonstrate a Great Variability in Morphology, Physiology, and Ecological Function

Akinetes are dormant cells of cyanobacteria species from the Nostocales and Stigonematales orders, allowing these phototrophic bacteria to survive in harsh and starvation conditions. These spore-like thick-walled, nonmotile cells differentiate from vegetative cells in response to environmental fluctuations. They serve a perennating role as they maintain the ability to resume the morphology and functions of vegetative cells including the renewal of cell division after a long period of dormancy. Here, we review recent advances in studies of akinetes emphasizing environmental triggers, cellular responses, morphological, and structural changes that occur during akinete differentiation and germination. Variations in akinete formation, structure, and metabolism among different species are highlighted and their role in bloom formation of Nostocales species is demonstrated.