PANTOTHENIC ACID 627 



pantothenate in preventing growth inhibition was similarly delayed. The 

 disappearance of pantothenic acid from the culture medium of either 

 streptococci or Corynebacterium diphtheriae was quickly inhibited by 

 pantoyltaurine and promptly recurred after removal of pantoyltaurine. 

 By quantitative experiments, it was shown that the amount of panto- 

 thenic acid consumed in such a process by streptococci and other 

 organisms during normal growth was in considerable excess of their 

 ordinary needs. No correlation was apparent between the rate of destruc- 

 tion of pantothenic acid by an organism and the sensitivity of the 

 organism to pantoyltaurine. The process of pantothenic acid destruction 54 

 has been shown to be independent of growth and oxygen consumption, 

 but was associated with the presence of glucose and a casein hydrolyzate 

 (or related materials) and perhaps magnesium ions. Pantoyltaurine in- 

 hibited both growth and the destruction of pantothenic acid, but did 

 not prevent glycolysis appreciably. However, inhibition of glycolysis 

 prevented the inactivation of pantothenic acid. The concentrations of 

 pantoyltaurine (or other analogues) necessary to prevent the disappear- 

 ance of pantothenic acid from the medium varied over a 300-fold range 

 with strains of streptococci, of Corynebacterium diphtheriae, and of 

 Proteus morganii, but were correlated with the concentrations required 

 for inhibition of growth of the respective organisms. 



Pantothenic acid was found to be present in a bound form in two 

 strains of /^-hemolytic streptococci. Autolysis or enzymatic digestion 

 liberated free pantothenic acid, but even high concentrations of pantoyl- 

 taurine did not displace the pantothenic acid from the combined form. 

 Pantothenic acid which was loosely bound was released into saline solu- 

 tions, but pantoyltaurine did not decrease the quantity remaining with 

 the organism. Thus, no gross displacement of pantothenic acid occurred. 55 



From these results, it was concluded that pantoyltaurine acts as a 

 bacteriostatic agent by preventing the conversion of pantothenic acid 

 to a functional derivative in susceptible bacteria. 



In pantothenic acid-deficient yeast, pantoyltaurine does not inhibit 

 fermentation processes stimulated by pantothenic acid. 56 In Streptococcus 

 hemolyticus, 57 pantoyltaurine inhibits the rate of glycolysis slightly 

 (10-25 per cent), and the effect was prevented by pantothenic acid which 

 alone accelerates glycolysis to a slight extent. 57 The concentrations of 

 pantoyltaurine affecting glycolysis had no effect on growth. 



Pantoyltaurine depressed the growth of Streptococcus hemolyticus by 

 increasing the lag period and decreasing the rate of growth. 57 The 

 logarithmic period of growth involved two phases — an initial phase dur- 

 ing which the rate of growth was considerably decreased, as compared 

 with normal growth, and a later phase characterized by an almost normal 



