44 ORDER I. PSEUDOMONADALES 



when free are motile by means of polar fiagella. In pure culture also this type rarely, if ever, 

 produces large aggregates with the development here mentioned as characteristic for the 

 genus (Bavendamm, Die farblosen und roten Schwefelbakterien, Pflanzenforschung, Heft 

 2, 1924, 76). This, along with the other similarities, makes it doubtful whether future studies 

 will result in the retention of the genera Lamprocijsiis and Thiocystis side by side. Produce 

 bacteriochlorophyll and carotenoid pigments, coloring the cell masses purplish pink to red. 

 Capable of photosynthesis in the presence of hj'drogen sulfide, storing elemental sulfur as 

 globules inside the cells. 

 The type species is Lamprocystis roseopersidna (Kiitzing) Schroeter. 



1. Lamprocystis roseopersicina (Kiitz- Winogradsky reports that the cells fre- 

 ing, 1849) Schroeter, 1886. (Protococcus quently contain pseudovacuoles. 

 roseopersicinus Kiitzing, Species Algarum, Habitat: Mud and stagnant water con- 

 Leipzig, 1849, 196; Schroeter, in Cohn, taining hydrogen sulfide and exposed to 

 Kryptogamen-Flora von Schlesien, 3, 1, light; sulfur springs. 

 1886, 151.) Illustrations: Warming, Videnskab. 



ro.se.o.per.si.ci'na. L. adj. roseus rosy; Meddel. naturhistor. Foren., Kjobenhavn, 



Gr. noun persiCMS the peach (Persian apple); 1876, PI. VIII, fig. 3 g; Zopf, Z. Morphol. 



M.L. adj. roseopersicinus rosy peach (-col- d. Spaltpflanzen, Leipzig, 1882, PI. V, fig. 8, 



ored). 13; Winogradsky, Schwefelbacterien, Leip- 



Cells spherical to ovoid, 2 to 2.5 microns zig, 1888, PI. II, fig. 9-15; Bavendamm, Die 



in diameter, up to 5 microns long before cell farblosen und roten Schwefelbakterien, 



division. Motile by means of polar flagella. Jena, 1924, PI. II, fig. 3. 



Genus VIII. Amoebobacter Winogradsky , 18SS. 



(Schwefelbacterien, Leipzig, 1888, 71.) 



A.moe.bo.bac'ter. M.L. noun Amoeba a protozoan genus; Gr. noun amoebe change, trans- 

 formation; M.L. noun bacter a rod; M.L. mas.n. Amoebobacter changeable rod. 



Sulfur purple bacteria, usually occurring in aggregates composed of many individuals 

 without a characteristic common capsule. Slime formation can, nevertheless, be observed 

 with very small colonies. With growth of the individual cells, the capsule bursts and the 

 cell mass slowly moves out while the bacteria remain united. The colonies change their 

 shape during growth and in response to environmental influences; the individual cells ap- 

 pear motile and cause the movements of the entire colon3^ Winogradsky ascribes the co- 

 herence of the cell masses to the existence of interconnecting protoplasmic filaments be- 

 tween cells, but these have never been observed, and their occurrence is extremely doubtful. 

 It is much more probable that the bacteria are held together by mucus, though not so much 

 of the latter is produced as to form a clearly discernible capsule. Produce bacteriochloro- 

 phyll and carotenoid pigments. Capable of photosynthesis in the presence of hydrogen 

 sulfide, then storing sulfur as droplets inside the cells. 



The type species is Amoebobacter roseus Winogradsky. 



The characterizations of the genera Amoebobacter, Lamprocystis, Thiocystis, Thiocapsa 

 and Thiothece are based upon the arrangement of individual bacteria in a common capsule. 

 However, from Winogradsky's descriptions of Amoebobacter and from pure-culture studies 

 with Thiocystis and Lamprocystis, the capsules have been shown to vary considerably, de- 

 pending upon developmental stages and environmental conditions. Therefore 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, al)Out 2.5 to 3.5 microns in diameter and up to 6 microns in 

 length prior to cell division. 



1. Amoebobacter roseus. 



