62 Marine Microbiology 



have been developed for the cultivation of Thiomdum mafus 

 Hinze, a colorless sulfur bacterium at present included in the 

 Thiohacteriaceae. 



Early descriptions and illustrations of Thiovuhim have been 

 given by Miiller (13), Warming (20), Hinze (8), Lauterborn 

 ( 12 ) and Bavendamm ( 2 ) . The cells are round to ovoid, measur- 

 ing from 5 to 25 /». in diameter. They normally contain sulfur 

 inclusions, frequently concentrated at one end, but sometimes 

 filling the cells almost entirely. The cells multiply by longitudinal 

 fission preceded by constriction. The organism is extremely mo- 

 tile and rotates around an axis coinciding with the path of travel. 

 It is strongly chemotactic and as a result the cells concentrate in 

 white, sharply defined veils, consisting of separate, ever moving 

 cells. By staining fixed specimens, Hinze (8) demonstrated peri- 

 trichous flagellation with great difficulty. This has not been con- 

 firmed by subsequent authors, including Faure-Fremiet and 

 Rouiller (5), who in a cytological study discovered a polar cyto- 

 plasmatic organelle and structures resembling an endoplasmatic 

 reticulum. The importance of these findings for comparative 

 cytology was discussed by Murray (14). 



The first physiological studies on Thiovulum, conducted at 

 the Hopkins Marine Station by van Niel, Wijler and Lascelles, 

 (unpublished) showed that it is extremely microaerophilic, and 

 that, like in Beggiatoa, its sulfur inclusions are lost soon after 

 the medium has become devoid of H2S, whereupon the organisms 

 perish. Taking advantage of the chemotaxis of Thiovulum, Wijler 

 developed a method for its enrichment. A layer of decaying algae 

 (Ulva), placed on the bottom of jar filled with sea water, served 

 as a continuous source of HjS, and a slow trickle of seawater, 

 introduced near the bottom, provided a continuous supply of O2. 

 The overflow flushed out many contaminating organisms, and 

 Thiovulum grew in characteristic veils in areas where the opti- 

 mum H2S and O2 concentrations prevailed. Massive transfers 

 to a similar jar without algae could be maintained by adding 

 small amounts of Hl;S once or twice daily. 



Part of this work has been recorded by van Niel (16); the 

 present study is a further extension of it. 



