Page:Bergey's manual of determinative bacteriology.djvu/103

 Colorless sulfur bacteria always occurring singly; slightly curved, elongated ellipsoids or cylinders with broad, hemispherical ends. Width varies from 8 to 14 microns, length from 12 to 30 microns; most common size, 9 by 20 microns. Multiplication by constriction in the middle.

Cells actively motile by means of a single polar flagellum distinctly visible without special staining. It is 20 to 40 microns long, and, with respect to the direction of motion, always posteriorly placed. Rate of movement somewhat sluggish, about 800 microns per minute, probably on account of the high specific gravity of the cells.

Normally contain small sulfur droplets and, in addition, large, roughly spherical inclusions of calcium carbonate. Two to four such crystal masses almost fill a single cell. Under unfavorable conditions the calcium carbonate crystals may disappear before the sulfur globules.

Microaerophilic; apparently require hydrogen sulfide.

Habitat: Found in fresh-water environments containing sulfide and calcium ions, as in shallow basins and streams in the upper layers of the mud.

2. Macromonas bipunctata (Gicklhorn, 1920) Utermöhl and Koppe, 1925. (Pseudomonas bipunctata Gicklhorn, Cent. f. Bakt., II Abt., 50, 1920, 425; Utermöhl and Koppe, Arch. f. Hydrobiol., Suppl. Bd. 5, 1925, 235.)

bi.punc.ta′ta. L. bis twice; L. part. adj. punctatus punctate, dotted; M.L. adj. bipunctatus twice punctate.

Cells colorless, occurring singly; cylindrical with hemispherical ends, after cell division often temporarily pear-shaped. 3 to 5 by 8 to 12 microns. Multiplication by constriction in the middle.

Actively motile by means of a single polar flagellum, about 10 to 15 microns long, always posteriorly placed with respect to the direction of movement. Flagellum delicate, not visible without staining. Rate of movement sluggish, about 600 microns per minute. Probably this slow motion is due to the high specific gravity of the cells.

Normally contain calcium carbonate crystals as inclusions. These are in the form of large spherules, one or two of which nearly fill the individual cells. Sulfur globules have not been demonstrated with certainty as yet.

Microaerophilic, but it is uncertain whether hydrogen sulfide is required.

A second species that is like Macromonas bipunctata, except that the cells are smaller in size, has been named by Gicklhorn (op. cit., 50, 1920, 425). Pure-culture studies may show the two species to be identical as difference in size of cells has not been found to be significant elsewhere among sulfur bacteria.

Source: From stems, leaves, etc. of freshwater plants in ponds near Graz, Austria.

Habitat: Found in fresh-water environments containing calcium ions; but it has been found in sulfide-containing as well as in sulfide-free water. Also found in shallow basins and streams in upper layers of the mud.

Thi.o′vu.lum. Gr. noun thium sulfur; L. noun ovum egg; M.L. neut. dim. n. Thiovulum small sulfur egg.

Unicellular organisms, round to ovoid, 5.0 to 20.0 microns in diameter. Cytoplasm often concentrated at one end of the cell, the remaining space being occupied by a large vacuole. Multiplication by constriction which, in late stages, merges into fission. Actively motile; movements accompanied by rapid rotation. Flagellation not definitely demonstrated, but type of locomotion suggests polar flagellation. Normally contain sulfur globules in the cytoplasm; hence, these are frequently concentrated at one end of the cell.

It is difficult to establish distinct species. Those that have been described differ only in