t'AMILY THIORHODACEAE 



853 



orgaiiisni l)elongs in the genus Rhodo- 

 spin Hum. 



Cells: l.U by 8 to 18 microns; coiled to 

 occupy H to 4 turns, the latter commonly 

 4 microns wide by 4 microns long. These 

 dimensions agree with those of Rhodo- 

 spirilliun rubrum (Esmarch) Molisch and 

 the identity of the two organisms is 

 probable. 



Habitat: Found in red slime spots on 

 the side of a well. Mud and stagnant 

 bodies of water. 



Illustration: Migula, Sj'st. d. Bakt., 

 1, 1897, PI. Ill, fig. 7. 



Appendix: Three species have been 

 placed in the genus Thiospirillum with- 

 out convincing evidence that they con- 

 form to the generic diagnosis. 



Thiospirilluin agilis Kolkwitz. 



(Kolkwitz, Kryptogamenflora d. Mark 

 Brandenburg, 5, Pilze, 1909, 162; Thio- 

 spira agilis Bavendamm, Die farblosen 



und roten Schwefelbakterien, Pflanzen- 

 forschung, Heft 2. 1924, 116.) This is 

 not known to have been a purple bac- 

 terium and hence may represent a mem- 

 ber of the genus Thiospira. 



Thiospirillunt agilis var. polonica 

 Strzeszewski. (Bull. Acad. Sci., Cra- 

 covie, Ser. B, 1913, 322.) This also may 

 belong in the genus Thiospira. 



Thiospirillum pisticnsc Czurda. 

 (Cent. f. Bakt., II Abt., 92, 1935, 409.) 

 Not described as pigmented and does 

 not contain sulfur globules. Reported 

 to be a probable agent in the production 

 of hydrogen sulfide from sulfates or 

 sulfur. It may therefore be the spirillar 

 form of Vibrio desiilfuricans Beijerinck 

 or, being thermophilic, of Vibrio thermo- 

 desulfuricans Elion. 



Thiospirilltini winogradskii Omelian- 

 sky. (Cent. f. Bakt., II Abt., U, 1905, 

 764.) This is colorless and is included 

 in Thiospira. 



Genus XI. Rhabdomonas CohnZ 



(Cohn, Beitr. Biol. Pfl., /, Heft 3, 1875, 167; Mantegazzaea Trevisan, R. Inst. 

 Lombardo de Sci. e Lett., IV, Ser. 2, 12, 1879, 137; Rhabdochro7tiaiium Winogradsky, 

 Schwefelbacterien, Leipzig, 1888, 100; in part, Rhodocapsa Molisch, Die Purpur- 

 bakterien, Jena, 1907, 17.) From Greek rhabdos, a rod, and monas, a unit (cell). 



Purple sulfur 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 rela- 

 tively inconspicuous slime capsule which can be rendered visible by India ink. The 

 less distorted cell types are frequently motile, flagella polar. Produce bacterio- 

 chlorophyll 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 inside the cells. 



The status of this genus is doubtful. Winogradsky {loc. cit.) recognized the simi- 

 larity of its members to species of Chromatium and the occurrence of many inter- 

 mediate forms which make a sharp distinction between the two genera impossible . 

 He preferred the designation of Rhabdochrornatium as a sub-genus. Warming (Vi- 

 denskab. Meddel. naturhist. Foren., Kjobenhavn, 1876, 320 ff.), Nadson (Bull. Jard. 

 Imper. Bot. St. Petersb., 3, 1903, 116), van Niel (Arch. f. Mikrobiol., 3, 1931, 61), and 

 Ellis (Sulphur Bacteria, London and New York, 1932, 151) considered the species of 

 Rhabdochromatium as abnormal growth forms (involution forms) of corresponding 

 species of Chromatium, while Lauterborn (Verhandl. naturhistor.-medizin. Vereins, 

 Heidelberg, N.F., 13, 1915, 424), Buder (Jahrb. wiss. Bot., 58, 1919, 534) and Baven- 



