48 H. O. HALVORSON 



TABLE V 



EFFECT OF MINERALS ON THE INHIBITION OF SPORULATION OF 



B. cereits t. by a-picoLiNic acid or versene 



Concentration of the minerals found in the medium, see 1 able IV. 



inhibition with a-picolinic acid. The only mineral ions that 

 reverse the inhibition are zinc, cobaU, and nickel. It is to be 

 noted that manganese, magnesium, calcium, iron, and copper 

 do not have this effect, nor can we reverse the inhibition by 

 increasing the normal minerals of the medium fourfold. From 

 these data one might conclude that «-picolinic acid does bring 

 about its inhibition by removing some essential ion. If this is so, 

 then the ion must be bound more firmly than the ions of man- 

 ganese, magnesium, calcium, iron, and copper, but less firmly 

 than zinc, cobalt, and nickel ions. In the light of these results, 

 we also tried versene. It is to be noticed that versene, added to 

 the extent of 1.5 mg/ml, also interferes with sporulation; but the 

 effect of the versene can be overcome by doubhng the concen- 

 trations of the minerals which are normally present in the growth 

 medium. A general chelating asent such as versene must there- 

 fore have a different effect than the a-picolinic acid. If a-picolinic 

 acid is producing its effect through a chelating action, it must 

 have a rather specific effect upon some special mineral. It 

 would be interesting to pursue this further, but in view of other 

 interesting problems we have not taken the time to do so. 



