ORDER VII. BEGGIATOALES BUCHANAN, Ordo Nov.[1]
Beg.gi.a.to.a'les. M.L. fem.n. Beggiatoa type genus of the order; -ales ending to denote an order; M.L. fern. pi. n. Beggiatoales the Beggiatoa order. Cells occur mostly in trichomes in three of the families and singly in the fourth family. When in contact with a substrate, the motile organisms glide over the surface or show a slow, rolling, jerky type of motion. No flagella or other organs of locomotion are known. Non-motile trichomes may also occur. The trichomes may show bending and flexing. With respect to gliding and oscillating, the trichomes function as distinct units except in the genus Bacloscilla, where the trichomes show bending at the joints between the cells. Multi- plication is by transverse fission throughout the entire length of the trichomes or of the singly occurring cells; gonidia occur in one family, Leucoirichaceae. Do not possess chloro- phyll or phycocj^anin. Under favorable environmental conditions, sulfur globules, some- times in accompaniment with calcium carbonate crystals, may be found in or on the cells. Found in fresh-water (with or without hydrogen sulfide) and marine habitats, in soil and in decomposing organic matter, especially algae. Key to the families of order Beggiatoales. I. Cells occur in trichomes. A. Trichomes motile by means of a gliding type of motility when in contact with a sub- strate. 1. Cells, when growing in the presence of hydrogen sulfide, contain granules of sul- fur. Family I. Beggiatoaceae, p. 837. 2. Cells do not contain granules of sulfur, even when growing in the presence of hydrogen sulfide. Family II. Vitreoscillaceae, p. 844. B. Trichomes non-motile, although gonidia (single-celled, gliding, reproductive cells) occur. Family III. Leucoirichaceae, p. 850. II. Cells occur singly and show a rolling, jerky type of motility when in contact with a substrate. Family IV. Achromatiaceae, p. 851.
FAMILY I. BEGGIATOACEAE MIGULA, 1894.[2]
(Migula, Arb. Bakt. Inst. Karlsruhe, 1, 1894, 238; in part, Leuco-Thiohacteria Bavendamm, Die farblosen und roten Schwefelbakterien, Pflanzenforschung, Heft 2, 1924, 102.) Beg.gi.a.to.a'ce.ae. M.L. fem.n. Beggiatoa type genus of the family; -aceae ending to
denote a family; M.L. fem.pl.n. Beggiatoaceae the Beggiatoa family.
837
