Apr. 28,1923 
Oxidation of Sulphur in Black Alkali Soils 
303 
Nathanson (<?), who first studied the Thiobacillus group, of which 
Thiobacillus B (not T. ihiooxidans) is a representative, stated that thio¬ 
sulphate is oxidized to sulphate and tetrathionate, with the production 
of free sulphur; however, on sodium sulphid agar plates, when free 
sulphur is formed abundantly in a nonbiological way, this sulphur is 
oxidized by the bacteria. The reaction proposed by Nathanson 
(3Na2S203-f-50=Na2S40e4-2Na2S0J could hardly be justified, particu¬ 
larly in view of the fact that the sulphur was supposed to be produced 
in a purely nonbiological way, by the interaction of the tetrathionate 
with the remaining thiosulphate, and was not supposed to play any 
part in the reaction. Beijerinck (j), who identified Nathanson's organ¬ 
ism with his T. ihioparus^ then suggested the following reaction: 
Na 2 S 203 4 - O = Na 2 S 04 +S. 
But Jacobsen (4), who worked in Beijerinck’s laboratory, found that 
the same organism oxidized elemental sulphur quantitatively to sulphate, 
which would again hardly justify Beijerinck's formula, if the organism 
was the same. Trautwein (12), however, obtained the separation of 
elemental sulphur from thiosulphate only in crude cultures of the organ¬ 
isms; but, in pure culture, no separation of elemental sulphur was 
found. At the same time a large part of the thiosulphate was trans¬ 
formed to sulphate. At first he thought the following reaction to be 
justified: 
Na2S203 -}- 4 O -f" H2^ “ Na2S04 -h H2SO4. 
In view of the fact that the reaction of the medium did not turn acid 
and that a large quantity of persulphate was formed, he finally con¬ 
cluded that the reaction takes place as follows: 
I. 4Na2S203+12 0 = 4Na2S206. 
II. 3Na^S203+ 5 0=Na2S206+2Na2S04. 
In the investigations carried on in this laboratory with pure cultures 
of Thiobacillus By it was found that this organism transforms thiosul¬ 
phate into persulphate, sulphate, and elemental sulphur, with only a 
limited production of acid (Ph changed in culture solution from 9.8 to 
6.4 or 7.0). When T. ihiooxidans is added to the culture solution, the 
elemental sulphur separated by the Thiobatillus B is rapidly oxidized to 
sulphuric acid and the final reaction may go down from Ph 9.8 to Ph 1.2 
as a result of the action of the two organisms. The culture solution 
used in this case consists of 5 gm. sodium thiosulphate, i gm. sodium 
bicarbonate, 0.2 gm. dipotassium phosphate, o.i gm. magnesium chlorid, 
o.i gm. ammonium chlorid, 0.25 gm. calcium chlorid, and 1,000 cc. of 
tap water. 
These discrepancies in the type of reaction that takes place when 
thiosulphate is acted upon by sulphur-oxidizing bacteria can be explained 
by the fact that different workers used different forms of a closely related 
group of organisms; in some cases the culture used possibly contained 
not one organism but a mixture of two or more organisms. Thiobacillus 
By isolated in this laboratory and closely related, in its morphology and 
physiology, to T. thioparus and allied forms studied by Nathanson {8)n 
Beijerinck (z), Trautwein {12) y and others (4), was possibly contaminated 
in some cases by T. thiooxidanSy which oxidizes actively elemental 
sulphur and is described by Waksman and Joffe (15). T. thioparus will 
act upon sulphur compounds under distinctly alkaline conditions, as in 
