Endospore – A differentiated cell formed within cells of certain Gram-positive bacteria that are extremely resistant to heat and other harmful conditions and agents.
Endopsore are the resting stage during the life cycle of some bacteria, formed in response to adverse conditions. The bacterial cell changes into a partially dehydrated core, enclosed in a multilayered protein coat. On return to favorable conditions the spore germinates and reverts back to the normal vegetative form of the organism and continues its life cycle.
Endospores can remian viable for long periods of time, potentially thousands of years.