246 



SELMAN A. WAKSMAN AND J. S. JOFFE 



the same action. A detailed study of the influence of stimulants 

 on the oxidation of sulfur by a pure culture of Thiobacilllus 

 thiooxidans is presented in table 2. 



The medium was buffered with phosphoric acid and mono- 

 potassium-phosphate to a pH of about 3.0 It was distributed 



TABLE 2 

 Influence of stimulants on the oxidation of sulfur 



'Titration = cubic centimeter of j^ NaOH necessary to neutralize 1 cc. of 

 culture, with phenolphthalein as an indicator. 



in 100 CC. portions in 250 cc. Erlenmeyer flasks containing 1 

 gram portions of powdered sulfur and the proper amounts of 

 Cas (P04)2, where present. The flasks were plugged with cotton 

 and sterihzed in flowing steam, for thirty minutes, on three 

 consecutive days. The organic substances were sterilized separ- 

 ately, then added to the sterile medium. The flasks were all 

 inoculated with one drop of the same pure culture and incubated 



