THE FORMATION OF SPORES BY BACTERIA 129 



DPA has already progressed to the point where heat-resistant spores 

 have been formed. We have examined the inhibited cultures for DPA 

 and find that very small amounts are present. It is to be noted that a 

 few heat-resistant spores are formed, so that the ethyl oxamate does 

 not block the synthesis of DPA completely, but it does interfere with 

 the synthesis enough so that more than 95 per cent of the spores that 

 are formed are heat-sensitive. The amount of DPA found in such 

 preparations is slightly more than one would expect if one assumes that 

 the heat-resistant spores have their normal content and the heat-sensi- 

 tive spores have none. It is possible, therefore, that some DPA may be 

 present also in the heat-sensitive spores. 



Somewhat similar results are obtained with diethyl pimelate. This 

 inhibitor, however, interferes with the development of normal vegeta- 

 tive cells if it is added to the culture at time, or very early in the 

 growth of the vegetative cells. The vegetative cells look abnormal, and, 

 in fact, many of them lyse before they can begin to produce spores. 

 This inhibitor may very well interfere with the synthesis of cell walls. 

 If the inhibitor is added after the pH has started to rise (at which 

 time the production of vegetative cells has been completed and pre- 

 sumably there is no further synthesis of cell wall), we find that the 

 inhibitor does not interfere with the production of spores, but the 

 spores produced are heat-sensitive, as shown in Table VIII. In fact, the 

 results are almost identical to those obtained with ethyl oxamate. Here 

 again, better than 95 per cent of the spores are heat-sensitive. These 

 heat-sensitive spores appear to be perfectly normal, as far as staining 



TABLE VIII 



The Effect of Time of Addition of Diethyl Pimelate (M/lOO) 



on Sporulation 



For purposes of counting, cells were spun down and resuspended in M/lOO 

 phosphate buffer, pH 7.2. 



Vegetative cells and germinated spores are killed immediately on exposure to 

 octyle alcohol (0.06ml/ 100ml H2O). 



