Motion of Colonies

Several organisms have been described which exhibit colonial motility when grown on a solid medium. 

The colonies exhibited not only linear motion but also a slow rotary movement. The direction of rotation of 200 to 300 colonies observed was counterclockwise, with the exception of two colonies in which it was clockwise. 

Endospores. Endospores are bodies produced within the cells of a considerable number of bacterial species. They are more resistant to unfavorable environmental conditions, such as heat, cold, desiccation, osmosis, and chemicals, than the vegetative cells producing them. However, it is debatable if such extreme conditions -actually occur in nature. For instance, the resistance of spores to high temperatures is a laboratory phenomenon and probably never occurs in a natural environment. 

The bulk of evidence indicates the existence of a close relationship between spore formation and the exhaustion of nutrients essential for continued vegetative growth. Sporulation is a defense mechanism to protect the cell when the occasion arises. 

Spore formation is limited almost entirely to two genera of rodshaped bacteria Bacillus (aerobic or facultatively anaerobic), and Clostridium (anaerobic or aerotolerant). With one possible exception, the common spherical bacteria do not sporulate. Some spore-bearing species can be made to lose their ability to produce spores. When the ability to produce spores is once lost, it is seldom regained. SporMation is not a process to increase bacterial numbers because a cell rarely produces more than one spore. 

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