Talk about akinetes.

Under unfavorable conditions, some Cyanobacteria form resistant spores called akinetes - enlarged vegetative cells with a thickened outer wall. Akinetes are dormant cells. They are resistant to cold and drought (desiccation). They also accumulate and store various essential materials, thus allow the Cyanobacteria to survive under unfavorable environmental conditions. Once conditions become more favorable for growth, the akinete can then germinate back into a vegetative cell.