i68 SULPHUR BACTERIA 



Family 6. — AMCEBOBACTERIACEAi. 



Literature. — Winogradsky (2), 1888; Migula (3), 1900; 



Bergey (i), 1923 ; Bavendamm (i), 1924. 

 Cells united into clusters usually enclosed in slime. When 

 movement takes place the cells move in unison. 



Genus i. — Amcebobacter (Winogradsky). 



Description. — A peculiar group of three species. The cells 

 are enclosed in a slime sheath, and slowly move inwards or 

 spread outwards in unison inside the slime. As a result there 

 is a slow alteration in the shape and mass of the community 

 of cells. This united action of the cells was explained by 

 Winogradsky as being due to contractile plasma threads which 

 bound the cells together, but neither he nor Lauterborn was 

 able to see them. It is, however, difficult to explain these 

 co-ordinated movements except by postulating the existence of 

 such threads. There is also another character of interest. The 

 slime envelope is made up of two layers, an outer which is 

 strongly refractive, and an inner which is feebly refractive. 

 The cocci on the opening of the slime cyst do not separate, but 

 move out together, leaving an empty shell. They then attach 

 themselves to some object in the water and whilst in attachment 

 exhibit those slow changes of form which are characteristic of 

 Amceba. Also in each cell a perceptibly large vacuole can be 

 discerned. 



Whilst in attachment, and before slime formation has pro- 

 ceeded very far, the cells close in until they are all huddled 

 together, and then they again spread out in extended formation. 

 It is not known whether the activating force of such move- 

 ments is spontaneous, or whether the movement takes place in 

 response to external injfluences. Winogradsky considers that the 

 presence of hydrogen sulphide in the water is responsible for 

 these movements, but has not adduced proof in support of his 

 statement. If the cells are connected by plasma threads, Amoeho- 

 bacter must be regarded as a loosely compacted coenobium. 



Amcebobacter roseus (Winogradsky). 

 Literature. — Winogradsky (2), 1888 ; Macgregor Skene, 

 1914 ; Lauterborn (7), 1915. 



