FAMILY I. THIORHODACEAE 53 



PI. XXXIX, fig. 1-2; Tokuda, Botau. from 0.5 to 0.7 by 0.6 to 1 micron (Issat- 



Magaz., Tokyo, 50, 1936, 339, fig. 1-23. chenko, Recherches sur les microbes de 



I'ocean glacial arctique, Petrograd, 1914, 



12. Chroniatium miniitissiniuin Wino- 253), and 1 to 3 by 2 to 5 microns (Issat- 



gradskjr, 1888. (Schwefelbacterien, Leipzig, chenko, Borodin Jubilee Volume, 1929?, 9). 



1888, 100.) Illustrations : Winogradsky, op. cit., 1888, 



mi.nu.tis'si.mum. L. sup. adj. minutissi- PI. IV, fig. 8; Miyoshi, Jour. Coll. Sci., Imp. 



mtfs very small. Univ., Tokyo, Japan, 10, 1897, PI. XIV, 



Cells about 1 to 1.2 by 2 microns. Also fig. 18. 



FAMILY II. ATHIORHODACEAE MOLISCH, 1907. 



(Die Purpurbakterien, Jena, 1907, 28.) 



A.thi.o.rho.da'ce.ae. Or. pref. a without; Gr. noun ihium sulfur; Gr. noun rhodum the 

 rose; -aceae ending to denote a family; M.L. fem.pl.n. Athiorhodaceae (probably intended 

 to mean) the family of the non-sulfur red bacteria. 



Unicellular bacteria, of relatively small size, occurring as spheres, short rods, vibrios, 

 long rods and spirals. Motility is due to the presence of polar flagella. Gram-negative. They 

 produce a pigment sj^stem composed of bacteriochlorophyll and one or more carotenoids, 

 coloring the cells yellowish brown, olive-brown, dark brown or various shades of red. Color 

 usually not observable with single cells but only with cell masses. Generally microaero- 

 philic, although many representatives may grow at full atmospheric oxygen tension. Capa- 

 ble of development under strictly anaerobic conditions, but only in illuminated cultures by 

 virtue of a photosynthetic metabolism. The latter is dependent upon the presence of ex- 

 traneous hydrogen donors, such as alcohols, fatty acids, hydroxy- and keto-acids, and does 

 not proceed with the evolution of molecular oxygen. Those members which can grow in the 

 presence of air can also be cultivated in darkness, but only under aerobic conditions. 



The growth requirements of some of the species in this family have been reported by 

 Hutner (Arch. Biochem., 3, 1944, 439; Jour. Bact., 52, 1946, 217; Jour. Gen. Microbiol., 4, 

 1950, 286) ; his findings are incorporated in the descriptions which follow. 



Key to the genera of family Athiorhodaceae. 



I. Cells rod-shaped or spherical, not spiral-shaped. 



Genus I. Rhodopseudomonas , p. 53. 

 II. Cells spiral-shaped. 



Genus II. Rhodospirillum, p. 58. 



Genus I. Rhodopseudomonas Kluyver and van Niel, 19S7, emend, van Niel, 1944- 



(Includes Rhodobacillus Molisch, Die Purpurbakterien, Jena, 1907, 14; Rhodobacterium 

 Molisch, ibid., 16; Rhodococcus Molisch, ibid., 20; Rhodovibrio Molisch, ibid., 21; Rhodocystis 

 Molisch, ibid., 22; Rhodonostoc Molisch, ibid., 23; Rhodosphaera Buchanan, Jour. Bact., S, 

 1918, 472; Rhodorhagus (sic) Bergey et al.. Manual, 2nd ed., 1925, 414; Rhodomonas Kluyver 

 and van Niel, Zent. f. Bakt., II Abt., 94, 1936, 397; not Rhodomonas Orla-Jensen, Cent. f. 

 Bakt., II Abt., 22, 1909, 331 ; Kluyver and van Niel, in Czurda and Maresch, Arch, f . Mikro- 

 biol., 8, 1937, 119; Rhodorrhagus Bergey et al.. Manual, 5th ed., 1939, 905; van Niel, Bact. 

 Rev., 8, 1944, 86.) 



Rho.do.pseu.do.mo'nas. Gr. noun rhodum the rose; Gr. adj. pseudes false; Gr. noun 

 monas monad, unit; M.L. fem.n. Pseudotnonas a bacterial genus; M.L. fem.n. Rhodopseudo- 

 monas the rose Pseudomonas. 



Spherical and rod-shaped bacteria, motile by means of polar flagella. Gram -negative. 



