Habitat: Widely distributed in mud and stagnant water. Mass development under conditions of relatively high sulfide concentrations and low pH in environments exposed to light.
Illustrations: Nadson, op. cit., 1912, Pl. III, fig. 3-12; van Niel, Arch. f. Mikrobiol., 3, 1931, fig. 8, p. 66.
2. Chlorobium thiosulfatophilum Larsen, 1952. (Jour. Bact., 64, 1952, 187.)
thi.o.sul.fa.to′phi.lum. M.L. noun thiosulfatum thiosulfate; Gr. adj. philis loving; M.L. adj. thiosulfatophilus thiosulfate-loving.
Cells indistinguishable from those of Chlorobium limicola.
Color: As in Chlorobium limicola.
Strictly anaerobic, obligatory photosynthetic bacteria. Utilize sulfides, sulfur, thiosulfate, tetrathionate and molecular hydrogen as oxidizable substrates; produce sulfate from inorganic sulfur compounds. Unable to grow in organic media free of oxidizable, inorganic sulfur compounds.
Distinctive characters: Differs from Chlorobium limicola in its ability to oxidize thiosulfate and tetrathionate.
Source: Isolated from marine and freshwater mud.
Habitat: Same as for Chlorobium limicola.
Genus II. Pelodictyon Lauterborn, 1913.
(Allgem. botan. Ztschr., 19, 1913, 98; Verhandl. naturhistor.-medizin. Vereins, Heidelberg, N.F. 13, 1915, 431.)
Pe.lo.dic′ty.on. Gr. adj. pĕlos dark-colored; Gr. noun dictyon net; M.L. neut. n. Pelodictyon a dark-colored net.
Sulfur green bacteria, individual cells ovoid to distinctly rod-shaped, producing rather extensive mucoid capsules and generally united into large colonies of characteristic shapes. Non-motile. Contain chlorophyllous pigments different from the common green plant chlorophylls and from bacteriochlorophyll. Capable of photosynthesis in the presence of hydrogen sulfide, but do not store sulfur globules inside the cells.
The type species is Pelodictyon clathratiforme (Szafer) Lauterborn.
Key to the species of genus Pelodictyon.
I. Cells united in colonies in a net-like fashion.
1. Pelodictyon clathratiforme.
II. Cells arranged in tightly packed colonies without net-like structure.
- A. Colonies composed of irregularly arranged cell-masses, extending in three dimensions.
2. Pelodictyon aggregatum.
- B. Colonies consisting of parallel strands and extending in two dimensions.
3. Pelodictyon parallelum.
1. Pelodictyon clathratiforme (Szafer, 1910) Lauterborn, 1913. (Aphanothece clathratiforme Szafer, Bull. Acad. Sci., Cracovie, Sér. B, 3, 1910, 162; Lauterborn, Allgem. botan. Ztschr., 19, 1913, 98; also see Verhandl. naturhist.-medizin. Vereins, Heidelberg, N.F. 13, 1915,430.)
clath.ra.ti.for'me. L. part. adj. clathratus latticed; L. noun forma shape, form; M.L. adj. clathratiformis lattice-like.
Cells generally rod-shaped, ranging from slightly elongated ovoids to distinct rods, often vacuolated, about 0.5 to 1.5 by 2 to 4 microns, producing rather wide slime capsules. Characteristically united into three-dimensional colonies which present a net-like appearance with mazes of about 10 to 50 microns. Non-motile.
Color: Yellowish green.
Abnormal cell forms (involution forms) not uncommon, consisting of elongated and curved, forked, or club-shaped and swollen rods, occasionally suggesting rudimentary branching at the extremities. Such cells
