FAMILY THIORHODACEAE 



The type species is Thiocystis violacea Winogradsky. 



Key to the species of genus Thiocystis. 



I. Individual cells more than 2 microns in width. 



1. Thiocystis violacea. 

 II. Individual cells about 1 micron or less in width. 



2. Thiocystis riifa. 



847 



1. Thiocystis violacea Winogradsky. 

 (Winogradsky, Schwefelbacterien, Leip- 

 zig, 1888, 65; Planosarcina violacea 

 Migula, in Engler and Prantl, Die na- 

 turl. Pflanzenfamilien, /, la, 1895, 20.) 

 From Latin violaceus, violet-colored. 



Cells: About 2.5 to 5.5 microns in 

 diameter, spherical to ovoid. Swarmers 

 actively motile by means of polar fla- 

 gella. 



Colonies: Small, inside a common cap- 

 sule, containing not over 30 cells. Sev- 

 eral such colonies form loosely arranged 

 aggregates, most characteristically com- 

 posed of about 10 to 20 colonies in a single 

 capsule. The result is a nearly spherical 

 zoogloea. In small colonies, the cells 

 appear as rather distinct tetrads; in 

 larger colonies, the cells become some- 

 what compressed and the tetrad-like 

 arrangement may be lost. 



In pure cultures, the species often fails 

 to produce the characteristic capsules; 

 the organisms then occur as actively 

 motile single cells or diplococci, with 



little or no slime formation. No pseudo- 

 capsules are formed. 



Habitat: Mud and stagnant water con- 

 taining hydrogen sulfide and exposed to 

 light; sulfur springs. 



Illustrations: Zopf, Zur IMorphologie 

 der Spaltpflanzen, Leipzig, 1882, PI. V, fig. 

 12; Winogradsky, loc. cit., PI. II, Fig. 1-7. 



2. Thiocystis rufa Winogradsky. 

 (Schwefelbacterien, Leipzig, 1888, 65.) 

 From Latin rufus, red. 



Cells: Less than 1 micron in diameter. 

 Color red, usually darker than in the 

 type species. When the cells are stuffed 

 with sulfur globules, the aggregates 

 appear almost black. 



The common gelatinous capsule usu- 

 ally contains a far greater number of 

 closely packed individual colonies than 

 is the case in Thiocystis violacea. 



Habitat : Mud and stagnant water con- 

 taining hydrogen sulfide and exposed to 

 light; sulfur springs. 



Illustration: Winogradsky, loc. cit., 

 PI. II, fig. 8. 



Genus VII. Lamprocystis Schroeter. 



(In part, Clathrocystis Cohn, Beitr. Biol. Pfl., 1, Heft 3, 1875, 156; in part, Cohnia 

 Winter, in Rabenhorst, Kryptogamen-Flora, 2 Aufl., 1884,48; Schroeter, Die Pilze 

 Schlesiens, in Cohn, Kryptogamen-Flora von Schlesien, 3, 1, 1886, 151; Cenomesia? 

 de Toni and Trevisan, in Saccardo, Sylloge Fungorum, 8, 1889, 1039; Lankasteron 

 Ellis, Sulphur Bacteria, London and New York, 1932, 135.) From Greek lampros, 

 bright, shining, and kystis, sac or bladder. 



Purple sulfur bacteria which form more or less large aggregates of cells enclosed 

 in a common gelatinous capsule. Individual cells spherical to ovoid. Small aggre- 

 gates closely resemble those of Thiocystis, even to the extent of the tetrad-like ar- 

 rangement of cells in the small colonies. Behavior of the large aggregates during 

 development appears to be different; the small individual cell groups or colonies do 

 not emerge from the slime capsule until the initially relatively compact cell mass 

 becomes broken up into smaller clusters, these eventually forming a somewhat net- 



