Dormant form of bacterial cells in unfavourable environmental conditions. To survive over long periods (sometimes many years) and under the most adverse conditions, bacteria form spores with a solid, extremely resistant shell and cease their metabolic activity. If the external conditions become favourable again, the spores activate and germinate by breaking open the outer shell and becoming permeable to water and nutrients. A distinction is made between endospores, exospores and myxospores, as well as cysts.
Bacterial spores have a high resistance to active substances of disinfectants, which can be overcome by certain active ingredients or special pH values.