LONGEVITY OF BACTERIA 45 



is why many food products have to be heated for such a long time, 

 or to such a high temperature to keep them. 



The manner of formation of spores within the body of the organ- 

 ism is characteristic. They develop within the cell body and hence 

 are called " endospores." They are formed by the bacilli and spirilla, 

 but not by the cocci. The beginning of spore formation is marked 

 by a granulation of the cell contents. As the process proceeds the 

 granules become larger and eventually fuse and collect at one por- 

 tion of the cell which is then surrounded by a spore wall. The spore 

 may be either smaller or larger than the mother cell. In the latter 

 case there is a bulging of the mother cell. The spore may be equa- 

 torial, polar, or intermediate within the cell depending on its position. 

 When situated equatorially and larger than the mother cell it gives 

 to it a boat-shape appearance (clostridia) . If situated at the pole 

 and large, we have the capitate or drumstick appearance. When 

 bacteria are found in chains and spores form in the end, there is a 

 tendency for them to occur in adjacent ends of contiguous cells. 

 A cell usually forms only one spore ; hence, this cannot be considered 

 a process of reproduction. 



When the spores are brought under favorable conditions of food 

 supply, temperature, and moisture they germinate. The process 

 differs according to species. In some species the spore ruptures at 

 the pole and the young cell emerges in such a way that its long axis 

 is in the same direction as the long axis of the spore, thus leaving 

 the spore membrane still visible at one of the poles. In other species 

 the spore germinates equatorially and the young cell emerges with 

 its long axis at right angles to the long axis of the spore. In still 

 other species there is no rupturing of the spore, but germination 

 occurs by a gradual elongation and absorption of the spore. 



Longevity of Bacteria. Due to their method of multiplication 

 there is no such condition as old age among bacteria since both 

 daughter cells are similar in age and composition. It is well known 

 that while in the spore condition many organisms can survive for 

 over two decades. Both the spore-forming and non-spore-forming 

 organisms have been obtained from soil which had been kept in 

 bottles in an air dry condition for more than fifty years. Recently 

 Sarcina lutea and other well-known air organisms have been obtained 

 from a Mastodon uncovered by the recession of the ice in Siberia. 

 This animal must have been covered for hundreds of years. This 

 would, therefore, seem to indicate that the longevity of bacteria 

 may be extremely great. 



