Although bacteria from about a half dozen genera can form spores, the most common spore-formers are members of the genus Bacillus and the genus Clostridium . Both are gram positive rods, but Bacillus are aerobic or facultatively anaerobic whereas Clostridium are anaerobic. Each genus contains organisms that are pathogenic. The spore, which may survive for prolonged periods in the environment, may infect and germinate inside the body. The ability to verify endospore production helps in the identification of bacteria.
Further information is derived from the appearance of the endospore.
It may be found in a central, subterminal or terminal position and may be equivalent to or larger than the diameter of the parent cell. The spore coats provide a high degree of the resistance of the endospore. However, they also prevent dyes from entering the cell. The endospore stain method uses heat to help malachite green penetrate the spore surface. Water will remove this stain from vegetative cells, but not from the endospores.