<P> The endospore consists of the bacterium's DNA, ribosomes and large amounts of dipicolinic acid . Dipicolinic acid is a spore - specific chemical that appears to help in the ability for endospores to maintain dormancy . This chemical accounts for up to 10% of the spore's dry weight . </P> <P> Endospores can survive without nutrients . They are resistant to ultraviolet radiation, desiccation, high temperature, extreme freezing and chemical disinfectants . Thermo - resistant endospores were first hypothesized by Ferdinand Cohn after studying Bacillus subtilis (pictured to the right) growth on cheese after boiling the cheese . His notion of spores being the reproductive mechanism for the growth was a large blow to the previous suggestions of spontaneous generation . Astrophysicist Steinn Sigurdsson said "There are viable bacterial spores that have been found that are 40 million years old on Earth--and we know they're very hardened to radiation ." Common anti-bacterial agents that work by destroying vegetative cell walls do not affect endospores . Endospores are commonly found in soil and water, where they may survive for long periods of time . A variety of different microorganisms form "spores" or "cysts," but the endospores of low G + C gram - positive bacteria are by far the most resistant to harsh conditions . </P> <P> Some classes of bacteria can turn into exospores, also known as microbial cysts, instead of endospores . Exospores and endospores are two kinds of "hibernating" or dormant stages seen in some classes of microorganisms . </P> <P> Bacteria produce a single endospore internally . The spore is sometimes surrounded by a thin covering known as the exosporium, which overlies the spore coat . The spore coat, which acts like a sieve that excludes large toxic molecules like lysozyme, is resistant to many toxic molecules and may also contain enzymes that are involved in germination . It is composed of keratin and other core specific proteins, which makes the endospore extremely hardy . The cortex lies beneath the spore coat and consists of peptidoglycan . The core wall lies beneath the cortex and surrounds the protoplast or core of the endospore . The core contains the spore chromosomal DNA which is encased in chromatin - like proteins known as SASPs (small acid - soluble spore proteins), that protect the spore DNA from UV radiation and heat . The core also contains normal cell structures, such as ribosomes and other enzymes, but is not metabolically active . </P>

Describe what a spore is in relation to bacteria