FAMILY III. THIOBACTERIACEAE 



81 



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 constric- 

 tion 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 mo- 

 tion, 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 hy- 

 drogen sulfide. 



Habitat: Found in fresh-water environ- 

 ments containing sulfide and calcium ions, 

 as in shallow basins and streams in the upper 

 layers of the mud. 



2. Macromonas bipunctata (Gicklhorn, 

 1920) Utermohl and Koppe, 1925. (Pseudo- 

 nonas bipunctata Gicklhorn, Cent. f. Bakt., 

 [I Abt., 50, 1920, 425; Utermohl and Koppe, 

 A.rch. f. Hydrobiol., Suppl. Bd. 5, 1925, 235.) 



bi.punc.ta'ta. L. bis twice; L. part. adj. 

 punctatus punctate, dotted; M.L. adj. bi- 

 punctatiis twice punctate. 



Cells colorless, occurring singly; cylindri- 

 cal with hemispherical ends, after cell divi- 

 sion often temporarily pear-shaped. 3 to 5 

 by 8 to 12 microns. Multiplication by con- 

 striction in the middle. 



Actively motile by means of a single polar 

 flagellum, about 10 to 15 microns long, al- 

 ways posteriorlj^ placed with respect to the 

 direction of movement. Flagellum delicate, 

 not visible without staining. Rate of move- 

 ment sluggish, about 600 microns per min- 

 ute. 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 glo- 

 bules have not been demonstrated with 

 certainty as yet. 



Microaerophilic, but it is uncertain 

 whether hj^drogen 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 dif- 

 ference in size of cells has not been found to 

 be significant elsewhere among sulfur bac- 

 tei'ia. 



Source: From stems, leaves, etc. of fresh- 

 water plants in ponds near Graz, Austria. 



Habitat: Found in fresh-water environ- 

 ments 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. 



Genus III. Thiovulum Hinze, 1913.* 

 (Ber. d. deutsch. bot. Ges., 31, 1913, 195.) 



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 cj^to- 

 plasm; 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 



* Prepared by Prof. Dr. Alexander Janke, Technische Hochschule, Vienna, Austria, De- 

 cember, 1954. 



