70 Marine Microbiology 



stances demonstrates the importance of chemotactic locomotion 

 for survival. 



The principle of the enrichment technique developed by 

 Wijler resembles closely that of the method used by Winograd- 

 sky (21) for cultivating Beggiatoa in a flow of hquid medium. 

 It is therefore probable that the application of conventional con- 

 tinuous culture procedures will also be fmitful for the culti\'ation 

 of other colorless sulfur bacteria, particularly of those which are 

 chemotactic or sessile; stationary cultivation of purified material 

 may then prove feasible for chemotactic and activily motile 

 organisms by means of the gradient method here described for 

 Thiovulum. 



SUMMARY 



Thiovulum cells obtained by means of Wijler's enrichment 

 technique could be freed from contaminants by repeated migra- 

 tion tlirough sterile seawater. Stationary cultivation of purified 

 cell material was realised at 12-15 C in flasks wliere a concentia- 

 tion gradient of H2S and O2 was established between a sulfide- 

 containing agar layer and an overlaying seawater medium aerated 

 locally near the top. In this manner cultures were obtained which 

 were considered pure since no contaminants could be detected 

 by subculturing in various liquid media. The success of the de- 

 scribed method depends on the degree of contamination of the 

 enrichment material and the capacity of the cells to withstand a 

 sufficient number of purification steps. 



The sulfur inclusions of the organism proved to be orthorom- 

 bic. The cells were gram-negative and devoid of catalase. Electron 

 micrographs showed the presence of numerous flagella. 



ACKNOWLEDGMENT 



The stimulating advice and help of Prof. Dr. C. B. van Niel 

 in the initiation and performance of this study is gratefully ac- 

 knowledged. The author is indebted for expert cooperation to 

 Dr. A. L. Houwink and Miss W. E. de Boer who carried out the 

 election microscopy and permitted incorporation in this paper 

 of part of the results; he expresses his thanks to Dr. D. R. Kreger, 



