866 



MANUAL OF DETERMINATIVE BACTERIOLOGY 



Cells: Generally single, nearly spheri- 

 cal, diameter without slime capsule 

 variable, depending upon medium, I'ang- 

 ing from 0.7 to 4 microns. In young 

 cultures actively motile by means of 

 polar fiagella; motility soon ceases in 

 media which are or become alkaline. 

 Copious slime production in media at 

 pH above 7. In strongly alkaline cul- 

 tures abnormal cell-shapes occur in the 

 form of irregular, swollen and distorted 

 rods, often having the appearance of 

 spore-bearing cells, simulated by the 

 production of fat bodies. In sugar-con- 

 taining media egg-shaped cells, meas- 

 uring as a rule 2.0 to 2.5 by 2.5 to 3.5 

 microns, are frequently found. Gram- 

 negative. 



Color : Anaerobic cultures develop with 

 brown color, ranging in shade from 

 a light, dirty greenish-brown to a dark 

 brown. Cultures grown in the presence 

 of oxygen are distinctly red. As in the 

 case of Rhodopseudonionas capsulatus, 

 the brown color of an anaerobic culture 

 can be changed to red by shaking with 

 air, light stimulating the color change. 

 Color due to bacteriochlorophyll and 

 carotenoid pigments. The large ma- 

 jority of cultures of this species produces 

 in addition a water-soluble, non-caro- 

 tenoid, bluish-red pigment which diffuses 

 into the culture medium. 



Gelatin is not liquefied, and growth 

 with single amino acids appears some- 

 what erratic. No definite correlations 

 have been observed. 



Development is possible over a wide 

 pH range, extending from at least 6.0 

 to 8.5. 



All cultures exhibit an unpleasant pu- 

 trid odor. 



Requires for optimal development 

 higher concentrations of yeast extract 



as a supply of growth factors than either 

 Rhodopseudonionas palustris or Rhodo- 

 pseudomonas capsulatus and is more 

 sensitive to low fatty acid concentra- 

 tions. With 0.2 per cent propionate in 

 a neutral medium, no growth occurs; 

 caproic and pelargonic acids are toxic in 

 concentrations below 0.1 per cent. On 

 the other hand, tartrate and gluconate 

 can serve as oxidation substrates, as can 

 also ethanol, glycerol, mannitol, sorbi- 

 tol, glucose, fructose and mannose in 

 0.2 per cent concentrations. 



In sugar-containing media, acid is pro- 

 duced; the pH may drop to below 4.0 

 before development ceases. Acid pro- 

 duction from glucose occurs both in 

 presence and absence of air, and in 

 illuminated as well as in non-illuminated 

 cultures. In cultures exposed to light, 

 the acid usually disappears later on. 



Thiosulfate is not oxidized; hydrogen 

 oxidation has not been observed. 



Oxygen does not prevent growth; 

 colonies develop on the surface of agar 

 plates exposed to air, with a red pig- 

 mentation. Capable of strictly an- 

 aerobic development in illuminated cul- 

 tures by photosynthesis. 



Temperature optimum below 30°C. 



Distinguishing properties: Spherical 

 cell-shape in most media; brown color of 

 anaerobic and red pigmentation of 

 aerobic cultures; growth with 0.2 per 

 cent tartrate, gluconate, ethanol, glyc- 

 erol, mannitol, sorbitol, glucose, fruc- 

 tose and mannose; failure to grow with 

 0.2 per cent propionate. 



Habitat: Regularly found in stagnant 

 bodies of water and in mud. 



Illustrations: Molisch, loc. cil., Plate 

 II, fig. 15; van Niel, loc. cil., fig. 7-8, 

 p. 19; fig. 39-45, p. 96; fig. 46-54, p. 97. 



Genus II. Rhodospirillum Molisch emend, van Nicl. 



(Molisch, Die Purpurbakterien, Jena, 1907, 24 ; van Niel, Bact. Rev., 8, 1944, 86; the 

 genus now includes the genus Phaeospirillum Kluyver and van Niel, Cent. f. Bakt., 

 II Abt., 9Jt, 1936, 396.) From Greek rhodon, red and M.L. spirillum, spirillum. 



Spiral-shaped bacteria, motile by means of polar fiagella. Gram-negative. 



