and carotenoid pigments, coloring the cell masses purplish to red. Capable of photosynthesis, in the presence of hydrogen sulfide, whereby elemental sulfur is formed as an intermediate oxidation product which is deposited as droplets inside the cells.
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 rufa.
1. Thiocystis violacea Winogradsky, 1888. (Schwefelbacterien, Leipzig, 1888, 65.)
vi.o.la′ce.a. L. adj. violaceus violet-colored.
Cells about 2.5 to 5.5 microns in diameter, spherical to ovoid. Swarmers actively motile by means of polar flagella.
Colonies: Small, inside a common capsule, containing not over 30 cells. Several such colonies form loosely arranged aggregates, most characteristically composed 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 somewhat 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 pseudocapsules are formed.
Habitat: Mud and stagnant water containing hydrogen sulfide and exposed to light; sulfur springs.
Illustrations: Zopf, Zur Morphologie der Spaltpflanzen, Leipzig, 1882, Pl. V, fig. 12; Winogradsky, op. cit., 1888, 65, Pl. II. Fig. 1-7.
2. Thiocystis rufa Winogradsky, 1888. (Schwefelbacterien, Leipzig, 1888, 65.)
ru′fa. L. adj. rufus red, reddish.
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 usually contains a far greater number of closely packed individual colonies than is the case in Thiocystis violacea.
Habitat: Mud and stagnant water containing hydrogen sulfide and exposed to light; sulfur springs.
Illustration: Winogradsky, loc. cit., Pl. II, fig. 8.
Genus VII. Lamprocystis Schroeter, 1886.
(In part, Clathrocystis Cohn, Beitr. Biol. Pfl., 1, Heft 3, 1875, 156; in part, Cohnia Winter, in Rabenhorst, Kryptogamen-Flora, 2 Aufl., 1884, 48; not Cohnia Kunth, Enumeratio plantarum, 5, 1850, 35; Schroeter, Die Pilze Schlesiens, in Cohn, Kryptogamen-Flora von Schlesien, 3, 1, 1886, 151.)
Lam.pro.cys′tis. Gr. adj. lamprus bright, brilliant; Gr. noun cystis the bladder, a bag; M.L. fem.n. Lamprocystis a brilliant bag.
Sulfur purple bacteria which form more or less large aggregates of cells enclosed in a common gelatinous capsule. Individual cells spherical to ovoid. Small aggregates closely resemble those of Thiocystis, even to the extent of the tetrad-like arrangement 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-like structure. This behavior has been ascribed to a change in the mode of cell division which at first appears to take place in three perpendicular planes and later presumably changes to a division in only two directions. Cells
