Endospores are dorment, environmentally resistant structures fromed by certain of bacteria. the majority of aerobic endospore-forming bacteria are harmless, saprophytic originisms found in soil and water. vegetative cells of aerobic-endospore-forming bacteria sporulate in response to adverse environmental conditions. the bacteria can persist in the endospore from for an extended period. under favorable conditions, such as readily available nutrient suply, endospores convert back to vegetative bacterial cells in a process known as germination. unlike vegetative cells, endospores resist environmental pressures, such as heat, desiccation, disinfection, and irradtion. Endospores are generally even-sized and refractile.