SURVEY OF PHOTOSYNTHETIC BACTERIA 467 



into a new pear-shaped cell; it becomes separated from the mother 

 cell by the formation of a septum in the connecting tube. 



Originally Rhodomicrobium was described as a nonmotile organism, 

 but since then it has been found that in young liquid cultures motile 

 cells, singly or in small groups of three or four, are present (19), 

 The single swarm cells arise from terminal elements of the colony, 

 and are peritrichously flagellated, in contrast to the swarm cells in 

 Hyphomicrobium cultures, which are polarly flagellated. 



Rhodo microbiiim can be grown photosynthetically in mineral media 

 supplied with an organic compound, lactate and ethanol being the pre- 

 ferred substrates, or with H2S. It does not require vitamins, and 

 appears to be obligatorily anaerobic. Thus it has not been cultivated 

 in the dark. 



The ability to grow at the expense of H2S, even though development 

 is slow under such conditions, suggests that Rhodomicrobium may 

 actually be a purple sulfur bacterium. 



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