44 



H. O. HALVORSON 



2.0x10® 

 '2.0x108 



oc-picolinic acid added at 3h 

 (1.2x10"5m) 



«-picolinic acid added at 2h 

 (1.2 x10"5M) 



— D n D 



addition of acid 



< 10- 



4 8 12 



Time in hours 



Fig. 6. Effect of dipicolinic acid on the sporulation of B. cereus T. 



with the subsequent utilization of the acids, while the pH 

 remains low and no spores result. If this material is added to the 

 culture after the pH begins to rise, there is no effect; the pH 

 rises normally, and the result is a normal spore crop. This 

 inhibitor may, therefore, interfere with the development of the 

 adaptive enzyme required for the utilization of the acetic acid. 

 In view of the unexpected result with a-picolinic acid, we felt 

 we should try other pyridine carboxylic acids. The results are 

 shown in Table I. It is seen from this that a-picolinic acid is the 

 only acid able to inhibit sporulation. 



TABLE I 



EFFECT OF PYRIDINE-CARBOXYLIC ACIDS ON THE SPORULATION OF B. CCVeUS T. 



Compound added 



Sporulation 



None -f 



Nicotinic acid (Pyridine-3-carboxylic acid) + 



Isonicotinic acid + 



Quinolinic acid + 



Pyridine-2,4-dicarboxylic acid + 



Pyridine-2,5-dicarboxylic acid + 



Dipicolinic acid (Pyridine-2.6-dicarboxylic acid) + 



a-Picolinic acid (Pyridine-2-carboxylic acid) — 



