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Oxidation of Thiosulphate by Certain Bacteria in Pure Culture. 



By William T. Lockett. 



(Communicated by Prof. P. F. Frankland, F.R.S. Received February 14, — 



Eead March 26, 1914.) 



In the course of investigations on the oxidation of thiosulphate on bacterial 

 sewage filters,* it was found that partially oxidised filtrates, still containing 

 appreciable quantities of thiosulphate, were slowly but completely oxidised by 

 simple aeration in the presence of living organisms, practically no oxidation 

 taking place in the control experiments with corresponding solutions rendered 

 sterile by steaming. 



Further investigations were undertaken with a view to the isolation of the 

 organism or organisms capable of bringing about this oxidation. 



Accordingly, gelatine and agar plates were made from active filtrates from 

 time to time and in general about 100 organisms per cubic centimetre were 

 noted, which were mainly of the non-liquefying and chromogenic types. 

 Subcultures in peptone water and peptone broth of several of the pre- 

 dominating types were made and after a few days' incubation added to 

 solutions of thiosulphate, which were then aerated under sterile conditions. 

 Many experiments were carried out in this manner without success. 

 Variations were introduced with regard to the age of the cultures and 

 the nature of the culture media, without effect, practically no oxidation of 

 the thiosulphate solutions taking place after several weeks' aeration. 



Subsequently it was observed that a bacteriological slide made of a 

 loopful of an active filtrate showed proportionately a greater number of 

 organisms per cubic centimetre than was indicated by the gelatine and 

 agar plates of the same solutions. Further, the microscopic appearance of 

 these — consisting mainly of one particular type — was very different from 

 that of the organisms previously subcultured. 



All attempts to grow the particular and characteristic organism on the 

 -usual media, e.g. nutrient gelatine and nutrient agar, failed. Minor investi- 

 gations indicated that the organism was most active in neutral solutions 

 containing only small quantities of organic matter, whilst ammonium sulphate 

 was a decided stimulant. 



Ultimately it was found on plating out very small quantities {e.g. O'OOl c.c.) 

 .of an active filtrate on a solid gelatine medium made without bouillon, but 



* ' Journ. Soc. Chem. Ind.,' June 16, 1913, vol. 32, No. 11, p. 579. 



2 L 2 



