48 ORDER I. PSEUDOMONADALES 



sulfur globules. Color of protoplasm not losen und roten Schwefelbakterien Jena, 

 recorded. 1924, 132) or Huber-Pestalozzi (Die Bin- 

 Habitat: Mud and stagnant water con- nengewasser, ^6, Heft 1, Das Phytoplankton 

 taining hj'-drogen sulfide and exposed to des Siisswassers, Stuttgart, 1938, 304) that 

 light. Probably widely distributed, but less the cells ever contain sulfur globules. Only 

 frequently recorded as the organism is not the red color is emphasized. Consequently, 

 so spectacular as the large Thiospirillum it is quite possible that this organism be- 

 jenense and Thiospirillum sanguineum. longs in the genus Rhodospirillum. 



Illustration: Warming, op. cit., 1876, PI. Cells 1.0 by 8 to 18 microns; coiled to 



X, fig. 12. occupy 1}4 to 4 turns, the latter commonly 



4 microns wide by 4 microns long. These 



5. Thiospirillum rufum (Perty, 1852) dimensions agree with those of Rhodospiril- 



Migula, 1900. {Spirillum rufum Perty, Bern, lum ruhrum (Esmarch) Molisch, and it 



1852, 179; Migula, S3^st. d. Bakt. 2, 1900, seems probable that the two organisms are 



1050.) identical. 



ru'fum. L. adj. rujus red, reddish. Habitat: Found in red slime spots on the 



General characteristics presumably those side of a well. Mud and stagnant bodies of 



of the genus, although it does not appear water. 



either from Perty's description or from that Illustration: Migula, Syst. d. Bakt., 1, 



of Migula {loc. cit.), Bavendamm (Die farb- 1897, PI. Ill, fig. 7. 



Genus XI. Rhabdomonas Cohn, 1875. 



(Cohn, Beitr. Biol. Pfl., 1, Heft 3, 1875, 167; Rhahdochromalium Winogradsky, Schwefel- 

 bacterien, Leipzig, 1888, 100.) 



Rhab.do.mo'nas. Or. noun rhabdus a rod; Or. noun monas a unit, monad; M.L. noun 

 Manas a protozoan genus; M.L. fem.n. Rhabdomonas the rod monad. 



Sulfur purple bacteria, as a rule occurring singly in the form of rather irregular, long 

 rods to filaments, exhibiting more or less pronounced swellings, or club and spindle shapes. 

 Filamentous structures, sometimes with constrictions, giving the filament the appearance 

 of a string of beads. These may be surrounded by a relatively inconspicuous slime capsule 

 which can be rendered visible by India ink. The less distorted cell t3^pes are frequently 

 motile b}^ means of polar flagella. Produce bacteriochlorophyll and carotenoid pigments, 

 coloring the cells pinkish to purplish red. Capable of photosynthesis in the presence of 

 hydrogen sulfide and then storing sulfur globules as an intermediate oxidation product in- 

 side the cells. 



The status of this genus is doubtful. Winogradsky (loc. cit.) recognized the similarity of 

 its members to species of Chromatium and the occurrence of many intermediate forms which 

 make a sharp distinction between the two genera impossible. He preferred the designation 

 of Rhabdochromatium as a sub-genus. Warming (Videnskab. Meddel. naturhist. Foren., 

 Kjobenhavn, 1876, 320 ff.), Nadson (Bull. Jard. Imp(5r. Bot. St. P^tersb., 3, 1903, 116), van 

 Niel (Arch. f. Mikrobiol., 8, 1931, 61) and Ellis (Sulphur Bacteria, London and New York, 

 1932, 151) considered the species of Rhabdochroinatium as abnormal growth forms (involu- 

 tion forms) of corresponding species of Chromatium, while Lauterborn (Verhandl. natur- 

 histor.-medizin. Vereins, Heidelberg, N.F., 13, 1915, 424), Buder (Jahrb. wiss. Bot., 68, 

 1919, 534) and Bavendamm (Die farblosen und roten Schwefelbakterien, Pflanzenforschung, 

 Heft 2, 1924, 129) favor generic rank. 



The type species is Rhahdoinonas rosea Cohn. 



Key to the species of genus Khabdomonas. 



I. Cells not containing calcium carbonate inclusions in addition to sulfur globules. 

 A. Cells more than 3 microns in width. 



1. Rhabdomonas rosea. 



