sporulation /spôr′yəlā″shən/ [Gk, sporos + L, atus, process] , 1. a type of reproduction that occurs in fungi, algae, and protozoa and involves the formation of spores by the spontaneous division of a cell into four or more daughter cells, each of which contains a part of the original nucleus. 2. the formation of a refractile body, or resting spore, within certain bacteria that makes the cell resistant to unfavorable environmental conditions. The cell regains its viability when conditions become favorable. See also spore.