858 ORDER VIII. MYXOBACTERALES 



by Jahn (op. cit., 1924). The definition of the family Myxococcaceae is now modified to per- 

 mit inclusion of the non-fruiting genus Sporocytophaga, as proposed by Stanier (op. cit., 6, 

 1942, 143). The fifth family, Cytophagaceae (Stanier, loc. cit.), consists of myxobacters which 

 produce neither fruiting bodies nor resting cells. 



Key to the families of order Myxobacterales. 



I. Neither fruiting bodies nor resting cells produced. 



Family I. Cytophagaceae, p. 858. 

 II. Resting cells produced. 



A. Resting cells cylindrical, not spherical or ellipsoidal. Fruiting bodies produced. 



1. Resting cells not contained in cysts. Fruiting bodies consist of mesenteric masses 

 or finger-like aggregations of resting cells. 



Family II. Archangiaceae, p. 863. 



2. Resting cells contained in cysts of definite shape borne on the fruiting bodies. 



a. Cysts angular. Vegetative cells always thick and short, with blunt, rounded 

 ends. 



Family III. Sorangiaceae, p. 866. 

 aa. Cysts rounded. Vegetative cells usually long and thin, with tapering ends. 

 Family IV. Polyangiaceae, p. 870. 



B. Resting cells (microcysts) spherical or ellipsoidal, surrounded by a distinct wall. 

 Fruiting bodies formed except in the genus Sporocytophaga. 



Family V. Myxococcaceae, p. 882. 



FAMILY I. CYTOPHAGACEAE STANIER, 1940. 

 (Jour. Bact., 40, 1940, 630.) 



Cy.to.pha.ga'ce.ae. ]\I.L. fem.n. Cytophaga type genus of the family; -aceae ending to 

 denote a familj^; M.L. fem.pl.n. Cytophagaceae the Cytophaga family. 



Flexible, sometimes pointed rods showing gliding motility. No fruiting bodies or resting 

 cells (microcysts) are formed. 



Genus I . Cytophaga Winogradsky, 1929. 



(Winogradsky, Ann. Inst. Past., 43, 1929, 578; includes Promyxobacterium Imsenecki and 



Solntzeva, Mikrobiologia, 14, 1945, 220; and Flexoscilla Pringsheim, Jour. Gen. 



Microbiol., 5, 1951, 145; in part Flexibacter Soriano, Re vista 



Argentina de Agronomia, 12, 1945, 120.) 



Cy.to'pha.ga. Gr. noun cytus hollow place, vessel, cell; Gr. v. phagein to devour; M.L. 

 fem.n. Cytophaga cell destroyer. 

 Description same as for the family. 

 The type species is Cytophaga hutchinsonii Winogradsk}-. 



Key to the species of genus Cytophaga. 



I. From soil. Not obligately halophilic. 



A. Vigorous growth on cellulose. Starch not utilized. 



1. Produce yellow pigment. 



1. Cytophaga hutchinsonii. 



2. Cytophaga lutea. 



2. Produces orange pigment. 



3. Cytophaga aurantiaca. 



