66 



A. KEYNAN AND M. HALMANN 



10 20 30 60 10 20 30 40 

 A minutes B 



120 300 



Fig. 1. Decrease in optical density of a spore suspension of B. licheniformis 

 at 0° after preincubation with alanine at 37' for different times. 

 Conditions of experiment : Spores were washed 30 times, heat shocked for 

 16 h at 60° in water, and suspended in 7 x 10- M phosphate buffer, pH 8. 

 Activation by L-alanine in final concentration = 1/75 M. Total volume 

 1.5 ml in test tubes of 6 mm diameter. Measurement of optical density in 

 Coleman Junior spectrophometer at 540 //. A, Decrease in optical density 

 of spore suspension incubated at 37 \ B, Decrease in optical density of 

 spore suspension incubated at ' after preincubation at 37 \ #, preincubated 

 for 0-2 min; A, preincubated for 4 min; -r, preincubated for lOmin. 



This can be shown from the preceding observations. In the 

 above experiment a drop in optical density started at 37° only 

 after 6 min. However, when spores which did not yet show a 

 decrease in optical density after preincubation for 4 min were 

 transferred to 0°, they showed germination. This means that the 

 'trigger reaction' occurred some time between the second and 

 the fourth minute, preceding any other measurable change. The 

 fact that the induction of germination precedes any measurable 

 change has been established previously by Harrell and Hal- 



