222 SULPHUR BACTERIA 



When first investigated, the thionic acid bacteria were 

 believed to be obligate autotrophs, obtaining their carbon 

 from the carbonic acid of the atmosphere, and their nitrogen 

 from nitrates or ammonium compounds. It was emphasized 

 that the source of their energy was the oxidation of thiosul- 

 phatc to the normal sulphate. Later investigations have 

 not borne out these statements. Thus Issatchenko and Salis- 

 mowskaja found that not only inorganic salts like ammonium 

 chloride, ammonium phosphate, and potassium nitrate, but 

 also organic compounds like asparagin and peptone could be 

 utilized as sources of nitrogen. It has also been necessary to 

 revise the opinions that were at first held regarding the 

 secretion of sulphur. The last-named investigators, working 

 with material from the salt marshes of the Crimea, from the 

 neighbourhood of Odessa, and from the Black Sea, found that 

 the secretion of sulphur was not a necessary accompani- 

 ment of the activities of these bacteria. This was con- 

 firmed by Trautwein who divided them into two classes 

 according to their capacity or incapacity for secreting free 

 sulphur.* 



Probably the chemical activities of these bacteria are not 

 as simple as they are represented in the equations formulated 

 by Beijerinck, and this is particularly true of those members 

 that do not secrete sulphur. 



Trautwein has shown that they are capable of considerable 

 adaptation, for he has isolated an organism of this class with 

 denitrifying powers. It reduces nitrates to nitrites and nitro- 

 gen. Further, the ferments trypsin, lipase, catalase, diastase 

 and oxidase have been identified in its cultures. With ex- 

 tended investigations the number of bacteria belonging to 

 this group has been increased. In addition to the two already 

 mentioned three species were isolated by Issatchenko and 

 Salismowskaja, and were named 



Thionsdure-hacteriimi Beijerinckii, 

 ,, Nathansohnii, 



,, Beijerinckii f. Jacobsenii. 



*See page 226 on the nomenclature of these bacteria. 



