868 



MANUAL OF DETERMINATIVE BACTERIOLOGY 



of tartrate, gluconate and citrate. In a 

 concentration of 0.2 per cent, ethanol is a 

 suitable substrate, whereas the carbo- 

 hydrates and their corresponding poly- 

 alcohols are not utilized. 



Thiosulfate is not oxidized; molecular 

 hydrogen can be used by some strains. 



Rather microaerophilic ; many strains 

 upon initial isolation incapable of growth 

 at atmospheric oxygen tension. Subse- 

 quent adaptation can be induced. But 

 even such adapted cultures exhibit nega- 

 tive chemotaxis to air. 



Capable of strictly anaerobic develop- 

 ment in illuminated cultures on the basis 

 of a photosynthetic metabolism. 



Temperature optimum generally be- 

 tween 30° and 37°C. 



Distinguishing properties: The most 

 important characteristics of the species 

 are the spiral shape, combined with the 

 ability to produce a red pigment with a 

 definite absorption maximum at 550 

 millimicrons in the intact cells. Diag- 

 nostically useful are the good growth in 

 media with 0.2 per cent ethanol, alanine, 

 asparagine, aspartate or glutamate, and 

 the inadequacy of similar concentrations 

 of carbohydrates and thiosulfate as 

 substrates. 



Habitat: Regularly present in stagnant 

 bodies of water and in mud. 



Illustrations: Molisch, loc. cil., Plate 

 I, fig. 5-7; van Niel, Bact. Rev., 8, 1944, 

 fig. 9-10, p. 19; fig. 11-16, p. 24; fig. 67- 

 75, p. 103; fig. 76-84, p. 104; fig. 85-90, 

 p. 106; fig. 91-96, p. 107. 



2. Rhodospirillum fulvum van Xiel. 

 (Bact. Rev., 8, 1944, 108.) From Latin 

 fulvurn., yellowish, tawny. 



Characteristic for the species is the 

 very small size of the individual cells. 

 These are not over 0.5 micron wide, and 

 generally not longer than 2.5 microns. 

 The most common shape consists of a 

 complete turn of about 1 by 1.5 microns. 

 In media with fatty acids as a substrate 

 the spirals appear somewhat steeper than 

 in fumarate, succinate or malate cul- 

 tures. Swollen individuals resembling 



vibrios are encountered in cultures which 

 do not appear quite healthy. Formation 

 of mucus or clumping has not been ob- 

 served. 



Gelatin is not liquefied; aspartate has 

 been the only amino acid capable of in- 

 ducing growth. Thiosulfate is not oxi- 

 dized. 



Color: Quite distinct from that of 

 Rhodospirillum rubrum; colonies and 

 stab cultures are a reddish-brown, while 

 liquid cultures often appear brownish- 

 orange. The color is due to bacterio- 

 chJorophyll and carotenoid pigments; 

 among the latter spirilloxanthin, as evi- 

 denced by the absence of an absorption 

 maximum at 550 millimicrons, is not 

 represented as a major constituent. 

 Does not produce water-soluble, diffus- 

 ible pigments. 



Capable of strictly anaerobic develop- 

 ment in illuminated cultures, due to 

 photosynthetic metabolism. 



Fatty acids and the four-carbon dicar- 

 boxylic acids are uniformly good sub- 

 strates; glutarate is not used. Ethanol 

 and glucose, in a concentration of 0.2 per 

 cent, have yielded satisfactory cultures; 

 other carbohydrates, as well as the corre- 

 sponding polyalcohols, have given nega- 

 tive results. 



Little information available concern- 

 ing pH and temperature relations. Be- 

 haves generally as a strict anaerobe; 

 adaptation to microaerophilic conditions 

 has not been achieved. Negative aero- 

 taxis very pronounced. 



Distinguishing properties: The small 

 size and the color of the cultures serve 

 as adeciuate criteria for its differentia- 

 tion from Rhodospirilluui rubrum. The 

 strictl}^ anaerobic nature and the failure 

 to grow with glutarate and various 

 amino acids except aspartate can prob- 

 ably be used as supplementary specific 

 properties. 



Habitat: Bodies of stagnant water and 

 mud. 



Illustrations: Van Xiel, loc. cit., fig. 

 97-102, p. 109. 



