Endospores form in some bacteria through a process called sporulation. This occurs under unfavorable environmental conditions, such as nutrient depletion or extreme temperatures. During sporulation, the bacterium forms a highly resistant, dormant structure known as an endospore. The endospore contains the bacterium’s DNA, surrounded by a tough protein coat that protects it from harsh conditions. Once the environment becomes favorable again, the endospore can germinate and give rise to a new, vegetative bacterial cell.