308 BIOLOGY OF PNEUMOCOCCUS 



ferent media containing simple and complex saccharides, organic 

 acids, alcohols, peptones, et cetera. Apart from the Type III spe- 

 cific polysaccharide he found only one other substance which 

 caused the elaboration of the specific enzyme by the SIII bacillus 

 and that was the aldobionic acid derived from the capsular poly- 

 saccharide of Type III Pneumococcus. When, however, he used an- 

 other aldobionic acid, namely, that derived from gum arabic — a 

 substance closely related immunologically to the Type III poly- 

 saccharide^ — no growth and, therefore, no enzyme could be ob- 

 tained in the synthetic medium. 



Dubos then learnt that the production of enzyme was also influ- 

 enced by the concentration of capsular polysaccharide in the me- 

 dium. The yield of enzyme rapidly increased with rising concentra- 

 tions of the soluble specific substance, but decreased when the 

 concentration exceeded 0.1 per cent and was inhibited by concen- 

 trations of 0.3 per cent or higher. Yeast extract, along with the 

 soluble specific substance, stimulated enzyme production, but Du- 

 bos' first preparations in this medium proved to be toxic for ex- 

 perimental animals. Yeast extract in itself was not toxic and only 

 when acted upon by cultures did it become so. However, Dubos was 

 able to reduce the toxicity of the enzyme preparation by lowering 

 the concentration of yeast extract to 0.03 per cent, the minimum 

 compatible with good yields of enzyme. 



Dubos then resumed his endeavors to produce a purer and more 

 potent preparation of the polysaccharide-decomposing enzyme 

 from the SIII bacillus, and in two communications (Dubos, 832 and 

 Dubos and Bauer 338 ) reported the results. It was first found that 

 the yield of enzyme was proportional within certain limits to the 

 amount of inoculum ; that it increased with a rise in the concen- 

 tration of capsular polysaccharide; and that 0.1 per cent of the 

 carbohydrate represented the optimal amount for the purpose. 

 After testing the influence of salt concentration in the medium on 

 the metabolic activity of the SIII bacillus, on the basis of the col- 

 lected data a method was devised which was described as follows 



