FAMILY THIORHODACEAE 



855 



to 60 microns in length. Shorter fila- 

 ments motile. Polar flagellate. Slime 

 formation may occur under special 

 conditions. Rose-red. Sulfur globules. 

 Probably an abnormal growth form of 

 Chromatium virosum. 



Habitat : Mud and stagnant water con- 

 taining hydrogen sulfide and exposed to 

 light; sulfur springs. 



Illustrations: Warming, loc. cit., PI. 

 VII, fig. 5; Winogradsky, loc. cit., PI. IV, 

 fig. 12; Molisch, loc. cit., PI. II, fig. 11-12. 



3. Rhabdomonas linsbaueri (Gickl- 

 horn) couib. nov. {Rhabdochromaliinn 

 linsbaueri Girklhorn, Ber. d. deut. bot. 

 Ges., 29, 1921, 312.) Named for the 

 botanist, K. Linsbauer. 



Cells: Resemble Rhabdomonas rosea. 



irregular, rod-shaped, 3 to 5 microns 

 wide, up to 30 microns in length. 



The characteristic feature of the 

 species, and the chief means of differen- 

 tiation, is the occurrence of calcium 

 carbonate inclusions in addition to the 

 sulfur globules in the cells. Whether 

 this is strictly an environmentally 

 conditioned characteristic, due to the 

 photosynthetic development of the bac- 

 teria in a medium rich in calcium ions, 

 so that calcium carbonate is precipitated 

 as the alkalinity increases, has not yet 

 been established, but seems possible. 

 In that case the identity of this species 

 with Rhahdomnaas rosea would become 

 evident. 



Source: From a ])ond near Graz, 

 -\ustria. 



Habitat: Fresh water. 



Genus XII. Rhodothece Molisch. 



(Die Purpurbakterien, Jena, 1907, 19.) From Greek rhodon, rose and theke, con- 

 tainer, capsule. 



Purple sulfur bacteria, occurring singly, not aggregated in families. Cells spheri- 

 cal, each surrounded by a rather wide capsule which is, however, rarely visible with- 

 out special staining. Motility not observed. Contain bacteriochlorophyll and caro- 

 tenoid pigments, coloring the cells reddish. Capable of photo.synthesis in the 

 presence of hydrogen sulfide; the cells then store sulfur globules, arising as an 

 intermediate oxidation product of the sulfide. 



In view of the experiences of Bavendamm and others that a number of representa- 

 tives of the purple sulfur bacteria, characterized by typical colonial aggregates when 

 found in nature, may develop as single cells in pure culture, it is quite conceivable 

 that the genus Rhodothece is synonymous with some other genus, e.g., Lamprocystis, 

 and that the two genera represent different growth forms induced by environmental 

 conditions. 



The type species is Rhodothece pendens Molisch. 



1. Rhodothece pendens Molisch. (Die 

 Purpurbakterien, Jena, 1907, 19.) From 

 Latin pendeo, to be suspended. 



Cells: Spherical, frequently occurring 

 as diplococci, occasionally as very short 

 chains or clumps of 3 to 5 individuals. 

 1.8 to 2.5 microns in diameter. Produce 

 rather abundant slime. Cells embedded 

 in individual capsules which are rarely 

 visible without staining (India ink). 

 Characteristic is the regular occurrence 

 of pseudovacuoles (aerosomes) which 



are supposed to keep the cells suspended 

 in liquid media. Refractive phenomena 

 due to the pseudovacuoles and to the 

 sulfur globules distort the cell shape 

 under ordinary illumination so that bac- 

 teria appear as polygons rather than 

 round cells. Usually 2 aerosomes and 2 

 sulfur globules per cell. Color not ob- 

 servable in individual bacteria. Cell 

 groups are rose-red. Motility not ob- 

 served. 



Habitat: Mud and stagnant water con- 



