Oxidation of Sulphur by Microorganisms. 3 



phosphates and bicarbonates, the acid produced interacts with 

 the basic element giving salts or acid salts tending to make the 

 medium less acid. But as soon as the neutralizing agent is used 

 up, the acid begins to accumulate, if there is an excess of elementary 

 sulfur in the medium. It is characteristic to note here one thing: 

 while the lack of acid production in the work of Winogradsky 

 was explained by the fact that the presence of sufficient carbonates 

 in the medium kept it at a neutral point, we find, in the case of 

 our organism, that the neutralization of the basic substances is 

 accomplished at a P H 3.6 to 2.0, which is a distinctly acid zone, 

 in fact even a more acid zone than the final acidity of the majority 

 of acid producing bacteria (lactic, acetic, etc.) and yeasts. 



We reported elsewhere that the sulfur-oxidizing bacteria, 

 which we have isolated and a complete description of which will 

 be published soon, produce a greater concentration of acids and 

 remain alive in that acid medium, than any biological phenomena 

 ever known. 



Age of Culture. 



Ph. 



Titrat. 

 Acidity c.c. 

 N/10 Alkali 

 per 5 c.c. 

 of Culture. 



Mgs. in 100 c.c. of 

 Solution. 



Sol. SO* 1 Insol. SO4 



Sulfur 

 Dissolved 

 Mgs. 



Soluble + 

 Phosphates 

 (as P) Mgs 

 in 100 c.c. . 



At start 



5-4 



0.8 



209 



0 



0 



45 





5-3 



0.9 



211 



0 





47 



4 " 



4.0 



1-3 



240 



40 



20 



60 



8 u 



2.7 



3-9 



444 



56 



87 



87 



12 " 



2-3 



5-0 



253. 



378 



140 



183 



23 *' 



2.4 



5-4 



300 



275 1 



115 



194 





2.1 



6.2 



314 



310 



158 



196 



30 " 



1.6 



9.6 



530 



360 



210 



194 



What we attempted in our work is not only the isolation of 

 strong sulfur-oxidizing organisms, but the production of acid at 

 such a rate and under such conditions that it should transform 

 insoluble tri-calcium phosphate into soluble phosphates and 

 phosphoric acid. The insoluble phosphates are used as neutral- 

 izing agents. 



1 The decrease is due to the fact that the determinations were based on separate 

 flasks, in which the ratio between the soluble and insoluble SO7 was not alike, for 

 some reason or another. 



