Cultivation and Properties of Thiovulum majus Hinze 69 



of flagella, distributed at random over the greater part of the cell 

 surface. The length of the flagella was about one-third of the 

 length of the cells; their width measiued between 100 and 150 A, 

 which is comparable to that of flagella of other bacteria. A more 

 detailed account on the electron microscopy of Thiovulum will 

 be published by de Boer et al. (3). 



DISCUSSION 



The necessity of using a specific inoculum for successful 

 enrichments with sea water from two difi^erent spots at the Dutch 

 coast suggests tliat the occurrence of Thiovulum is restricted to 

 a definite ecological zone, as may well be expected from its ex- 

 treme sensitivity to environmental conditions. 



The rediscovery of flagella, first observed by Hinze in 1913, 

 solves the problem of the mechanism of locomotion. The nega- 

 tive findings of previous authors may be explained by a high 

 sensitivity towards osmotic changes and other adverse conditions 

 since no flagella were observed in unfixed preparations even if 

 centrifuging had been omitted. The identity of the organism 

 studied by Faure-Fremiet and Rouiller with that studied by us 

 seems to be well-established by the unique characteristics they 

 have in common. 



Our results have demonstrated the possibility of isolating 

 Thiovulum and of growing it in stationary cultures. The success 

 of the method depends on the one hand on the degree of con- 

 tamination of the starting material which determines the num- 

 ber of successive washings needed to achieve purity; and on the 

 other hand on its capacity to survive these treatments. The rea- 

 son why enrichments with water from the North Sea were un- 

 satisfactor\' in these respects is not yet understood and is being 

 further investigated. 



The evidence obtained thus far is consistent with the as- 

 sumption that Thiovulum is a chemo-autotroph but far from suf- 

 ficient to prove this. Whether or not the oxidation of sulfide ful- 

 fils the energy requirements of the cell, it is certain that sulfide 

 and oxygen are of great significance in its metabolism. The sensi- 

 tivity of the organism to changes in concentration of these sub- 



