THE CULTURE OF THE SULPHUR BACTERIA 



59 



Jegunow bestow a second name to the aggregated bacteria, 

 namely Fountain Plate. 



By letting down into the fluid a very line and weighted 

 thread which had first been treated with very dilute ferric 

 chloride, and then with ammonia, so that tlic thread was 

 coloured a faint bluish-yellow, he was able to show some inter- 

 esting relationships between the organism and the medium. 

 Below the plate the thread turned black, following the for- 

 mation of ferrous sulphide. This demonstrated the presence 

 of hydrogen sulphide below the plate : — 



FeClg + 3NH4OH = Fe(0H)3 + 3NH4CI, 

 Fe(0H)3 + H2S = Fe^Ss + 6H,0. 



In the plate itself the bacteria were filled with globules 

 of sulpfhur, whilst above the plate the colour was taken out 

 of the thread by the action of the sulphate formed by the 

 bacteria. 



It must be stated that the phenomena described above 

 are not of frequent occurrence, and their incidence is probably 

 due to physical causes, in this case probably the presence of 

 slime. 



Macgregor Skene, working with raw cultures of purple 

 sulphur bacteria, concluded that when more favourable results 

 were obtained by the addition of certain organic compounds, 

 this was to be attributed not directly to the organic compounds 

 but to the ammonium sulphate liberated from these com- 

 pounds by saprophytic bacteria. The most vigorous develop- 



