62 SULPHUR BACTERIA 



He found further that 



[a) The purple bacteria grow better in dayhght than in 



red light. 



[b) The same bacteria grow better in red than in blue light. 



Bavendamm repeated the cultural methods of Skene for. 

 the coloured, and of Keil for the colourless, sulphur bacteria. 

 He also used successfully Lieske's mineral solution for the 

 cultivation of the iron bacteria. All the culture fluids received 

 an abundant supply of pure "calcium prascipitatum." In 

 one instance he found that the growth of a raw culture of 

 Lamprocystis obtained from a mass of decomposing Chara 

 was so abundant that colonies of the organism rose to the 

 surface in large numbers. By an ingenious arrangement, for 

 details of which the reader is referred to his book, he was able 

 to regulate the supply of oxygen and of sulphuretted hydrogen. 

 He obtained the following results : — 



1. HgS optimum supply 25 m.m. Hg pressure. 



2. O2 „ ,, 26 „ 



Hydrogen was added to raise the pressure to that of the 

 normal atmosphere. His raw cultures were disturbed by the 

 appearance on the surface of a thin whitish-yellow layer of 

 sulphur in which were embedded numbers of a small colourless 

 bacillus. By subculturing he finally obtained a growth of 

 Lamprocystis which did not form a surface layer of sulphur. 

 He satisfied himself that the culture was now pure by trans- 

 ferring some of it to sterile bouillon, a procedure which did 

 not result in bacterial growth taking place in this fluid. 



Experiments with Thioporphyra volutans. — A few tentative 

 experiments have been made with this organism by the author. 

 In nature it flourishes only in sea water containing organic 

 matter resulting from the decomposition of seaweed, or from 

 the presence of sewage. Both in nature and in artificial 

 cultures active growth results only if the supplv of oxygen 

 is limited. In nature this is secured by the rapid con- 

 sumption of the dissolved oxygen by the numerous aerobic 

 saprophytic bacteria that are also present. In the laboratory 



