THE BACTERIAL ENDOSPORE 37 



may be materially speeded up at these higher temperatures. 



A variety of dormant enzymes have since been found to 

 exist in spores, in addition to those mentioned above. These 

 become activated when the spores germinate or are ruptured 

 mechanically. In the dormant state they must be resistant to 

 heat, because such enzymes can be found in spores that are 

 germinated after heating. In fact, it appears from the work of 

 Church and Halvorson^^ that a higher activity may be obtained 

 from extract of spores following heat shock than from unheated 

 spores. Although these enzymes are resistant to heat in the 

 dormant state, they are heat sensitive following germination 

 and mechanical rupture of the spores. The mechanisms which 

 are involved in conferring heat resistance on spores also appear 

 to render them inactive. I shall not attempt to discuss this 

 further since it may be covered in the subsequent lecture. 



The third observation which I mentioned above, namely, 

 that spores contain the chemical dipicolinic acid, has also 

 proven to be a very powerful stimulus to researchers of spore 

 physiology. This observation, as well as the one concerning the 

 heat-resistant enzymes, was a natural consequence from Hills' 

 early discovery. Powell et al.^, while studying germination, 

 detected a number of organic compounds which had been 

 secreted during the process. They then proceeded to examine 

 the supernatants from germinated spore suspensions and, thus, 

 discovered that dipicolinic acid along with other materials was 

 released from the spores during germination. Among the other 

 materials were calcium ions and a spore peptide. The occurrence 

 of dipicolinic acid was of special interest because this was the 

 first time this chemical had been reported in a natural product. 

 A follow up of these studies has shown that dipicolinic acid is a 

 normal constituent of all spores of bacteria (both aerobes and 

 anaerobes) and that it is present in considerable quantities, 

 varying from 6% to 12% of the dry weight of normal spores. 

 As soon as these announcements were made, everyone who was 

 interested in spore research examined their spores for this 

 chemical and were able to confirm the observation of Powell. 



References p. 59 



