46 ORDER I. PSEUDOMONADALES 



Capable of photosynthesis in the presence of hydrogen sulfide, when the cells store elemen- 

 tal sulfur as droplets inside the cells. 

 The type species is Thiopoly coccus ruber Winogi'adsky. 



1. Thiopolycoccus ruber Winogradsky, taining hydrogen sulfide and exposed to 



1888. (Schwefelbacterien, Leipzig, 1888, 79.) light; sulfur springs. 



ru'ber. L. adj. rwber red. Illustrations: Winogradsky, loc. cil., PI. 



Cells spherical, about 1.2 microns in di- IV, fig. 16-18; Issatchenko, Recherches sur 



ameter. No motility observed. les microbes de I'ocean glacial arctique. 



Habitat: Mud and stagnant water con- Petrograd, 1914, PI. II, fig. 7. 



Genus X. Thiospirillum Winogradsky, 1888. 



{Ophidomonas Ehrenberg, Die Infusionstierchen, Leipzig, 1838, 43; Winogradsky, Schwe- 

 felbacterien, Leipzig, 1888, 104.) 



Thi.o.spi.ril'lum. Or. noun thium sulfur; M.L. dim.neut.n. Spirillum a bacterial genus; 

 Gr. noun spira a spiral; M.L. neut.n. Thiospirillum suUur Spirillum. 



Sulfur purple bacteria, occurring singly as spirally wound cells, motile by means of polar 

 flagella. Contain bacteriochlorophyll and carotenoid pigments, coloring the cells brownish 

 to purplish red. Capable of photosynthesis in the presence of hydrogen sulfide, during which 

 they produce and store, as an intermediate oxidation product, elemental sulfur in the form 

 of droplets inside the cells. 



The differentiation of species in this group has been based exclusively on observations 

 with material from natural collections and from laboratory mass cultures. The criteria 

 used are the size and shape of the spirals and the color of the organisms. Not a single repre- 

 sentative has so far been obtained and studied in pure culture, so that no information is 

 available concerning the constancy or variability of these characteristics. It is likely, how- 

 ever, that such properties may be greatly influenced by environmental factors. Hence, the 

 following key and descriptions of species are apt to be modified when more extensive studies 

 have been made. The published descriptions of some species make it seem probable that 

 they should not even be incorporated in Thiospirillum. 



The type species is Thiospirillum jenense (Ehrenberg) Winogradsky. 



Key to the species of genus Thiospirillum. 



I. Width of cells 2.5 microns or more. 



A. Color of cells, especially in masses, yellowish brown to orange-brown. 



1. Thiospirillum jenense. 



B. Color of cells deep red or violet. 



1. Cells long, typical spirals; clearly red. 



2. Thiospirillum sanguineum. 



2. Cells short, slightly curved, vibrio-shaped; color purple to violet-red. 



3. Thiospirillum viokiceum. 

 II. Width of cells less than 2.5 microns. 



A. Width of cells 1.5 to 2.5 microns. 



4. Thiospirillum rosenbergii. 



B. Width of cells about 1 micron. 



5. Thiospirillum rufum. 



1. Thiospirillum jenense (Ehrenberg, bacterien, Leipzig, 1888, 104; Thiospirillum 



1838) Winogradsky, 1888. (Ophidomonas cmssi<A« Hama, Jour. Sci. Hiroshima Univ., 



jenensis Ehrenberg, Die Infusionstierchen, Ser. B, Div. 2, Bot., 1, 1933, 157.) 



Leipzig, 1838, 44; Winogradsky, Schwefel- je.nen'se. M.L. adj. jenensis pertaining to 



