114 G. G. KRISHNA MURTY 



heat activation period was extended for longer than 90 minutes. Murty re- 

 ported that the activation of glucose oxidation in the same strain of spores 

 as used here required considerably longer time at 65 °C. This difference in 

 their work and ours may be due to difference in age and the method of 

 preparation of the spores. 



In order to further characterize the extent of the enzyme-activated sys- 

 tem, the oxidative capacity of the activated spore was examined with other 

 carbohydrates. The results indicated that gluconate, 2-ketogluconate, and 

 pyruvate were oxidized by the heat-activated spore, in addition to glucose. 

 However, hexosediphosphate, fructose-6-phosphate, maltose, ribose, arabin- 

 ose, lactose, and fructose were not oxidized. As will be detailed by Dr. Har- 

 lyn Halvorson, these results are consistent with the demonstration in spore 

 extracts of a non-phosphorylated and a phosphorylated shunt pathway and 

 an active tricarboxylic acid cycle for glucose metabolism. 



The oxidative capacity of heat-activated spores towards glucose remains 

 optimal for at least 2 hours after activation. However, the activation was 

 transient and steadily diminished during prolonged storage at 5°C. Follow- 

 ing 24 hour storage after heat-activation, the spore retained only 15% of 

 its glucose-oxidizing capacity. However, the results indicated that the glu- 

 cose-oxidizing capacity, which was largely lost during 24 hour storage of 

 heat-activated spores, was fully restored by a second heat shock treatment. 

 When the originally heat-activated spores were stored for periods longer 

 than 24 hours the extent of reactivation decreased. After one week of stor- 

 age at 5°C the glucose oxidation was irreversibly lost. The ultimately ir- 

 reversible loss in heat-activated spores may be due to a slow catabolism of 

 some endogenous component required for metabolic activity. Some of the 

 previous difficulty in demonstrating glucose oxidation may thus be related 

 to a prior heat-shock treatment followed by a prolonged storage period. 



The level of glucose oxidation by a spore preparation was also influenced 

 by the age of the spores. Freshly harvested, heat-activated spores had a neg- 

 ligible endogenous respiration and a Q02 (N) of 6 on glucose. The optimal 

 endogenous (Qo2(N)=5) and glucose oxidation (Qo2(N)=30) was found 

 in the same spore preparation which had been aged for at least 4 months 

 at -20 °C after harvesting. Storage up to 4 years did not increase the respi- 

 ratory level of the spore preparation. In both fresh and aged spores, heat 

 activation was required for respiratory activity. 



In spores of B. cereus var. terminalis glucose acted both as a substrate 

 for oxidation and as an agent for germination. The ability of glucose to act 

 under certain conditions as a substrate but not as a germinating agent was 

 shown when glucose was initially added at concentrations of less than 10"^ 

 M. However, when this concentration of glucose was added after a pro- 



