prokaryotic cell endospore BTO:0002779 http://purl.obolibrary.org/obo/cl.owl A rounded, inactive form that certain bacteria assume under conditions of extreme temperature, dryness, or lack of food. The bacterium develops a waterproof cell wall that protects it from being dried out or damaged. [database_cross_reference: GOC:tfm][database_cross_reference: ISBN:0618947256] bacterial spore