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MANUAL OF DETERMINATIVE BACTERIOLOGY 



Habitat: Regularly found in mud and 

 stagnant bodies of water. 



Illustrations: Molisch, loc. cit., Plate 

 I, fig. 1, 2; Plate II, fig. 10; van Niel, 

 Loc. cit., fig. 1-3, p. 18, and fig. 18-26, p. 90. 



2. Rhodopseudomonas gelatinosa (Mo- 

 lisch) van Niel. {Rhodocystis gelatinosa 

 Molisch, Die Purpurbakterien, Jena, 

 1907, 22; van Niel, Bact. Rev., 8, 1944, 

 98.) From Latin gclatio, freezing, indi- 

 cating solidification, or in this case, 

 clumping. 



Cells: In young cultures, short and 

 small rods, approximately 0.5 by 1 to 2 

 microns. In old cultures much longer, 

 up to 15 microns, and then irregularly 

 curved rods, often swollen and gnarled 

 in places up to 1 micron in width. In 

 this stage the cells bear some resemb- 

 lance to those found in old cultures of 

 Rhodopseudomonas palustris, but the 

 characteristic Mycobacterium-like clus- 

 ters of the latter are absent. Single 

 cells infrequent due to a copious mucus 

 production in all media which causes 

 the cells to clump together. While 

 young cells are actively motile by means 

 of polar flagella, motility is often diffi- 

 cult to ascertain as a result of the pro- 

 nounced tendency to conglomerate; the 

 individuals in the clumps appear to be 

 non-motile. Gram-negative. Gelatin 

 is liquefied; of the single amino acids 

 alanine, asparagine, aspartic and glu- 

 tamic acids appear generally satisfactory 

 substrates. 



Color: Quite distinctive in most an- 

 aerobic cultures as a pale, delicate, pink- 

 ish shade, rather peach-colored. Only 

 in the presence of rather high concentra- 

 tions of yeast extract (when a much 

 heavier growth is obtained than with low 

 concentrations supplemented with 0.2 

 per cent of various single oxidation sub- 

 strates) do the slimy cell masses appear 

 a dirty, faded brown. Color is due to 

 bacteriochlorophyll and carotenoid pig- 

 ments. Occasionally a water-soluble, 

 non-carotenoid, bluish-red pigment is 



produced which diffuses into the culture 

 medium. 



In yeast extract, growth occurs over a 

 pH range extending from at least 6.0 

 to 8.5. 



Cultures produce a characteristic 

 acrid odor. 



More sensitive to fatty acids than 

 other species of Rhodopseudomonas; with 

 0.2 per cent propionate no growth occurs. 

 The best single oxidizable substrates 

 appear to be ethanol, glucose, fructose 

 and mannose, as well as a variety of 

 amino acids. Citrate also permits good 

 growth; not, on the other hand, glycerol, 

 mannitol, sorbitol or tartrate in the 

 usual concentration of 0.2 per cent. 



Thiosulfate is not oxidized; behavior 

 towards molecular hydrogen unknown. 



More pronouncedly microaerophilic 

 than the other Rhodopseudomonas spe- 

 cies; most cultures cannot develop on 

 aerobically incubated slants or agar 

 plates. 



Capable of strictly anaerobic develop- 

 ment in illuminated cultures by virtue 

 of a photosynthetic metabolism. 



Temperature relations so far unknown. 



Distinguishing properties: The small 

 size of the individual cells, and the pro- 

 nounced clumping which causes the 

 cultures to be exceptionally stringy; the 

 unusual color of the cell masses; the 

 ability to liquefy gelatin, to utilize ci- 

 trate and a number of amino acids. 

 Correlated with these is the failure to 

 grow in media with 0.2 per cent pro- 

 pionate, tartrate and glycerol. 



Habitat: Regularly present in stagnant 

 bodies of water and in mud. 



Illustrations: Molisch, loc. cit., Plate 

 I, fig. 8; van Niel, loc. cit., fig. 55-60, 

 p. 99; fig. 61-66, p. 100. 



3. Rhodopseudomonas capsulatus (Mo- 

 lisch) van Niel. {Rhodonostoc capsu- 

 lalum Molisch, Die Purpurbakterien, 

 Jena, 1907, 23; van Niel, Bact. Rev., 8, 

 1944, 92.) From Latin capsula, con- 

 tainer (sheath). 



