Different microorganisms in different environments during sterilization have different resistance to the destructive principles that causes the organism or spore to die (lethality) Some extreme thermophile organisms have their optimal growth temperature at 110°C, whereas most vegetative cells are killed at 60°C. Some species (not necessarily spore formers) are highly radiation resistant. The chemical environment causes significant variance in the death rate of a microorganism. Very dense cell walls, spore coats, or slime layers outside the cell can severely limit the ingress of what is being used to sterilize the product.