1032 COMPREHENSIVE KEY 



Cells spherical to cylindrical. Develop in small clusters, the compact clusters of 4 to 20 

 cells being widely separated in an almost spherical and seemingly cartilagenous cap- 

 sule, the outer laj^er of which is neither sharply differentiated nor obviously deliques- 

 cent. As each cluster proliferates, it eventually separates into a number of smaller 

 clusters within the zoogloea. Single cells are rare. At some stage individual clusters 

 leave the mass as a result of either swelling and dispersion of the whole mass or a soften- 

 ing of the mass at one or more points. After separation, the cluster becomes motile. 

 The process of separation of clusters occupies 3 weeks. Generation time is approxi- 

 mately two days Thiocystis p. 4^ 



Cells spherical to cylindrical; heavily encapsulated, the capsules remaining attached to 

 form zoogloeae. The individual capsules are very thick. Following division the cells 

 become separated in space by the developing capsules and are eventually arranged 

 at an obtuse angle to each other. Swarming is preceded bj' a softening of the capsule 

 and an irregular rearrangement of the cells. Individual cells separate by a slow rota- 

 tory action and once free are actively motile (c/. Chromatium) . Cells are pale gray. 

 Sulfur granules are small and confined to the peripheral layer of cytoplasm 



Thiothece p. ^2 

 7. Cells spindle-shaped; 1.5 to 1.7 by 2.5 to 5.0 microns. Cell families may consist of a long 

 irregular body made up of cells 2 to 3 layers thick arranged in parallel fashion. When 

 separated from other cell masses the cells rearrange to form an open pyramidal net- 

 work in which the cells meet only at their tips. Colonies may be several hundred 

 microns across and resemble Hydrodictyon of the blue -green algae. Small cell groups 

 detached from the mass are motile; compact masses form under unfavorable condi- 

 tions. Individual cells contain an elongated vacuole and are pale in color; sulfur 

 is confined to the peripheral cytoplasm Thiodictyon p. 41 



Cells compressed into a compact mass; colored rose-red; surrounded by a capsule com- 

 posed of an inner, poorly refracting layer and an outer, strongly refracting layer. 

 Placed in a favorable environment, the cyst cracks and the cell mass slowly creeps out 

 (1 to 2 days). The empty cyst remains unchanged for some time. The group of cells 

 does not disperse but grows in an irregularly contoured mass. Whole families are 

 motile. Most cells are spherical. Division occurs only in one direction. Cells may be 

 compressed or may be freelj^ separated in the non-encysted state. There are rarelj' 

 more than two to four within a group in the colony. Thej' are continually changing 

 position and proximity in the colony. Internal colonial movement can occur without 

 much lateral movement. Coordinated lateral movement is amoeboid. Single cells oc- 

 casionally become isolated from the mass and then are drawn back. Masses ultimately 

 may separate into smaller groups. No capsular material can be discerned in the fami- 

 lies. Families can be penetrated by small motile bacteria with ease. Winogradsky 

 considered that the connection was via plasma threads, but he was unable to demon- 

 strate them. He considered the dense compact masses to occur in the presence of O2 

 and the open structure in the presence of hydrogen sulfide 



Aiiioebobacter p. 44 



Shapeless, thick aggregates of small spherical vividly colored cells; non-motile; do not 

 form hollow spherical structures. The extremely smooth surface of the colony suggests 

 a limiting capsular material, but no obvious capsule is visible. Eventually growth, in 

 the form of threads and flaps, appears on the surface, and cells become separated 



Thiopoly coccus p. 45 



