SPORE GERMINATION OF B. Ucheuiformis 65 



metabolism prevent the germination — at least in most species of 

 bacteria tested. These reactions have been shown to be part of the 

 metabolism of the germinating spore, but it is not yet possible 

 to define which of them is responsible for the beginning of 

 germination and therefore constitutes the 'prime event". 



It might be helpful in the study of this problem to find a 

 system in which it would be possible to separate the 'prime 

 event" ('trigger reaction") from later occurring metabolic steps. 

 Working with a strain of B. licheniformis we found that 

 'triggering', i.e. initiation of germination, can be brought about 

 under conditions which are distinct from those under which 

 germination of a 'triggered' cell can occur. Spores of this strain 

 could be 'triggered' by L-alanine at temperatures above 20°, and 

 after exposure to such temperatures for a short time were able 

 to germinate (as manifested by a drop in optical density) even 

 at a temperature as low as 0°. We interpret this to mean that the 

 'trigger reaction" can occur at a temperature higher than is 

 required for a subsequent m.etabolic step. UtiUsing this observa- 

 tion, and with the intention of investigating the initiation of 

 germination separately from its subsequent steps, an experiment 

 was designed in which the heat-activated spores were preincu- 

 bated with L-alanine at 37' for a few minutes, and were then 

 cooled to 15° or 18°. 



As previously stated, alanine failed to initiate activation in 

 cells treated directly at 15°. Nevertheless, optical density of 

 spore suspensions preincubated at 37° for a few minutes con- 

 tinued to decrease at 15\ The final drop in optical density at 

 15° and 18° depended on the duration and temperature of 

 preincubation. 



Fig. 1 presents data of such an experiment. Two minutes of 

 preincubation of a spore suspension at 37° are not enough for 

 germination to start after transfer to 0% but after 4 min of 

 preincubation, about 30% of the spores are activated. This can 

 be seen when the preincubated suspension is transferred to 0°. 



The 'prime event' starting the chain of reactions apparently 

 precedes in time the measurable manifestation of germination. 



References p. 70 



