How do bacterial spores help bacteria survive harsh conditions?

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Bacteria A scanning electron micrograph of gram-positive *Mycobacterium tuberculosis* bacteria, the cause of tuberculosis and scrofula.

To survive harsh environmental conditions, many bacteria undergo sporulation, a process that creates stable, dormant structures such as endospores, cysts, or exospores.1

These structures act as a protective mechanism triggered by nutritional deprivation. The formation of an endospore involves encasing a copy of the bacterial chromosome within multiple layers, including a thick peptidoglycan cortex and a rigid spore coat. This coat possesses keratin-like properties that provide significant resistance to lethal threats, including:1

Heat and freezing1
Desiccation (dehydration)1
Radiation1
Chemical exposure1

The extreme resilience of endospores is largely attributed to their exceptionally low internal water content. While in this dormant state, the bacteria exhibit no metabolic activity. Once favorable conditions return and nutrients become available, the spores are able to differentiate back into active, vegetative cells. Other structures, such as cysts, also provide resistance to harmful conditions, though generally to a lesser degree than endospores.1