crude cultures, have been greatly strengthened by studies with pure cultures of species of Chromatium. Thus van Niel (Arch. f. Mikrobiol., 3, 1931, 59) reported variations in width from 1 to 4 microns, and in length from 2 to 10 microns or even up to 50 microns; Manten (Antonie van Leeuwenhoek, 8, 1942, 164 ff.) found size differences of 1 to 14 microns with a pure culture of an organism that he identified as Chromatium okenii. Often the differences in size of a pure culture can be related to special environmental conditions. On account of such results a designation of species on the basis of size relations alone is manifestly unsatisfactory. Moreover, the available data do not suggest that differences in shape, color or arrangement of sulfur globules can be used more effectively. Lack of adequate experimental results with a sufficiently large number and variety of pure cultures prevents a more rational classification at present.
The previously proposed species have been listed below with their respective characteristics and arranged as far as possible in the order of decreasing width.
Two Chromatium species have been described as containing inclusions of calcium carbonate in addition to sulfur globules. As in the case of Rhabdomonas linsbaueri, it is not known whether this feature may be a direct consequence of the calcium ion content and pH of the environment and thus fail to have taxonomic significance.
The type species is Chromatium okenii Perty.
1. Chromatium gobii Issatchenko, 1914. (Recherches sur les microbes de l'ocėan
glacial arctique, Petrograd, 1914, 253.)
go′bi.i. M.L. gen. noun gobii of Gobi; named for Prof. X. Gobi.
Cells 10 microns by 20 to 25 microns.
Source: From sea water of the Arctic Ocean.
Habitat: Presumably ubiquitous in the colder portions of the Ocean at least.
Illustration: Issatchenko, loc. cit., Pl. II, fig. 12.
2. Chromatium warmingii (Cohn, 1875) Migula, 1900. (Monas warmingii Cohn, Beitr. Biol. Pfl., 1. Heft 3, 1875, 167; Migula, Syst. d. Bakt., 2, 1900, 1048.)
war.min′gi.i. Named for Eugene Warming, a Danish botanist; M.L. gen. noun warmingii of Warming.
Cells 8 by 15 to 20 microns, also smaller (Cohn).
Illustration: Cohn, op. cit., 1875. Pl. VI, fig. 11.
3. Chromatium linsbaueri Gicklhorn, 1921. (Ber. d. deut. botan. Ges., 39, 1921, 312.)
lins.bau′er.i. Named for K. Linsbauer, an Austrian botanist; M.L. gen. noun linsbaueri of Linsbauer.
Cells 6 by up to 15 microns (Gicklhorn); 6 to 8 microns in width (Ellis, Sulphur Bacteria, London and New York, 1932, 147) . Special characteristic is the occurrence of calcium carbonate inclusions. Otherwise resembles Chromatium okenii.
Source: From a pool in the Stiftingtal, near Graz, Austria.
Habitat: Fresh water.
Illustrations: Gicklhorn, op. cit., 1921, 314, fig. 1; Ellis, op. cit., 1932, 148, fig. 31.
4. Chromatium okenii (Ehrenberg, 1838) Perty, 1852. (Monas okenii Ehrenberg, Infusionsthierchen, Leipzig, 1838; Perty, Zur Kenntniss kleinster Lebensformen, Bern, 1852, 174.) This is the type species of
genus Chromatium.
o.ke′ni.i. Named for L. Oken, a German naturalist; M.L. gen. noun okenii of Oken.
Cells 5.6 to 6.3 by 7.5 to 15 microns (Cohn); minimum width 4.5 microns (Issatchenko, Borodin Jubilee Vol., 1929?, 8); with many transitions to Chromatium weissei (Winogradsky, Schwefelbacterien, Leipzig, 1888, 92). Also: 3.5 by 8 to 12 microns and varying in size from 1 to 15 microns (Manten, Antonie van Leeuwenhoek, 8, 1942, 164).
Illustrations: Cohn, Beitr. Biol. Pfl., 1, Heft 3, 1875, Pl. VI, fig. 12; Winogradsky, op. cit., 1888, Pl. IV, fig. 3-4; Issatchenko, Recherches sur les microbes de l'océan glacial arctique, Petrograd, 1914, Pl. II, fig. 9.
5. Chromatium weissei Perty, 1852.
