Characteristics Endospores are produced within cells and are refractile - light cannot penetrate them so that they are very easy to see in the phase microscope. See Figure below. They are resting structures, meaning that there is little or no metabolism inside the spore and it is a real form of suspended animation. Spores can survive for a very long time, and then regerminate. Spores that were dormant for thousands of years in the great tomes of the Egyption Pharohs were able to germinate and grow when placed in appropriate medium.
Spores are resistant to heat, radiation, chemicals, and dessication.
Spores are capable of detecting their environment and under favorable nutrient conditions germinating and returning to the vegetative state. Everything that is needed to function once returned to the vegetative state. Coats - Outside of the cortex are several protein layers that are impermeable to most chemcials. The formation of a spore is an expensive and complex process for the bacterial cell. Spores are only made under conditions where cell survival is threatened such as starvation for certain nutrients or accumulation of toxic wastes.