When some bacteria organisms sense that nutrients in its environment are low, they start to make structures called endospores through a process called the sporulation cycle. A single bacterial cell will make one endospore inside itself when nutrient sources are low, or if the cell is starving, and release it when the cell undergoes autolysis. Endospores are highly differentiated cells that are resistant to heat, chemicals, and radiation. They can survive in a dormant state until optimal growth conditions occur. This survival is due to its unique cellular structure. This unique structure is what differentiates endospores from vegetative cells. First, endospores have a core, also known as a protoplast. The core contains the spore chromosomal DNA, calcium dipicolinate, ribosomes, and other enzymes but it is not metabolically active. The calcium dipicolinate is thought to protects DNA and help make the call heat resistant. It also makes up 20% of the cell’s dry weight. Small Acid Soluble Proteins (SASPs) are also partly responsible for resistance in endospores. It protects from UV radiation chemicals that damage DNA. Next is the spore wall. It is the innermost layer surrounding to the spore and contains peptidoglycan. During vegetation it becomes the cell wall of the bacteria. After the spore wall comes the cortex. This also contains peptidoglycan and is the thickest layer of the endospore. Lastly is the coat. It is this layer that is the cause for impermeability of the endospore. When the endospore is ready to become an active bacterial cell it undergoes a process called germination. To become a vegetative cell, it must first undergo activation. During this step of germination, metabolic processes start and the spore coat is ruptured or absorbed. Next is the initiation of germination, which only happens if environmental conditions are favorable. The cortex of peptidoglycan will undergo autolysis and water will be taken up. The last step in germination is outgrowth. During this phase the cell will be able to start multiplying again.