FAMILY THIORHODACEAE 849 



colony. Winogradsky ascribes the coherence of the cell masses to the existence of 

 interconnecting protoplasmic filaments between cells, but these have never been 

 observed, and their occurrence is extremely doubtful. It is much more probable 

 that the bacteria are held together bj' mucus, though not so much of the latter is pro- 

 duced as to form a clearly discernible capsule. 



Produce bacteriochlorophyll and carotenoid pigments. Capable of photosyn- 

 thesis in the presence of hydrogen sulfide, and then store sulfur as droplets inside 

 the cells. 



The type species is Amoebobacter roseus Winogradsky. 



Since the characterization of the genera Amoebobacter, Lamprocystis, Thiocyslis, 

 Thiocapsa and Thiothece is based upon the arrangement of individual bacteria in a 

 common capsule, which, from Winogradsky 's descriptions of Amoebobacter and from 

 pure culture studies with Thiocystis and Lamprocystis, has been shown to vary con- 

 siderably, depending upon developmental stages and environmental conditions, it 

 is quite possible that future investigations will show the desirability of restricting 

 the number of genera. 



Key to the species of genus Amoebobacter. 



I. Cells spherical to ovoid, about 2.5 to 3.5 microns in diameter and up to microns 

 in length prior to cell division. 



1. Amoebobacter roseus. 



II. Cells distinctly rod-shaped, about 1.5 to 2 microns in width by 2 to 4 microns 

 in length. 



2. Amoebobacter bacillosus. 

 III. Cells spherical, quite small, about 0.5 to 1 micron in diameter. 



3. Amoebobacter granula. 



1. Amoebobacter roseus Winogradsky. Tokyo, Japan, 10, 1897, 158.) From 

 (Schwefelbactorien, Leipzig, 1888, 77.) Latin bacillus, resembling a rod. 

 From Latin roseus, rose. Cells rod-shaped, about 1.5 to 2 mi- 

 Cells spherical to ovoid, 2.5 to 3.5 crons by 2 to 4 microns. Cells contain 



microns in width and up to 6 microns pseudovacuoles (aerosomes). Sulfur 



in length. Motile. Often contain pseu- globules deposited exclusively in periph- 



dovacuoles. Cell-aggregates often form eral protoplasmic layer, usually quite 



transitory hollow spheres or sacks, with small. 



the bacteria occupying the periphery as Habitat : .Mud and stagnant water, con- 



a shallow layer. These are reminiscent of taining hydrogen sulfide and exposed to 



stages in the development of Lampro- light; sulfur springs. 



cystis. Illustrations: Zopf, Z. Morphol. d. 



Habitat: Mud and stagnant water Spaltpfl., Leipzig, 1882, PI. V, fig. 26-27; 



containing hj'drogen sulfide and exposed Winogradsky, loc. cit., PI. Ill, fig. 7. 

 to light; sulfur springs. Miyoshi's incomplete description of 



Illustrations: Winogradsky, loc. cit., Thiodsrmaroseum {loc. cit.), type species 



PI. Ill, fig. 1-6. of genus Thioderma, is sufficient to make 



practically certain that it is identical 



2. Amoebobacter bacillosus Winograd- with Amoebobacter bacillosus. The de- 

 sky. (Winogradskj-, Schwcfelbacterien, scription of Thiodiciyon elsgans Wino- 

 Leipzig, 1888, 78; Thioderma roseum gradsky (loc. cit.) suggests that it cannot 

 Miyoshi, Jour. Coll. Sci., Imp. Univ. be distinguished from this species. 



