1008 MANUAL OF DETERMINATIVE BACTERIOLOGY 



Thaxter proposed the term "pseudoplasmodium" as a satisfactory descriptive name 

 for the vegetative colony, while Jahn preferred the use of "swarm stage." Inasmuch 

 as the term "colony" in relation to bacterial growth implies large numbers of vege- 

 tative cells developing as a unit without regard for size, shape or structure, it is equally 

 suitable. Stanier (Bact. Rev., 6, 1942, 183) speaks of the condition as "reproductive 

 communalism." 



Pigmentation of the fruiting bodies is commonly employed in the differentiation 

 of species. Species that produce colorless cysts and some with black pigment have 

 been reported; in general the fruiting bodies are brightly colored in shades of yellow, 

 red, orange or brown. The color seems to originate in the slime or cyst walls rather 

 than in the encysted cells; its nature is not well understood. The Krzemieniewskis 

 (Bull. Acad. Polon. Sci. Lettres, Classe Sci. Math. Nat., S^r. B, Sci. Nat., I, 1937, 

 11) noted that the orange-red fruiting bodies of Sorangium compositum became gray- 

 brown in strong alkali ; the pigment was highly soluble in acetic acid and alcohol and 

 easily soluble in ether and chloroform. It was insoluble in benzol, carbon di-sulfide 

 and petroleum ether. They suggested that it was a carotin derivative rather than 

 true carotin. 



Beebe (1941, loc. cit.) found that the pigments of Polyangium fuscuin, Podangium 

 erectum, Myxococciis virescens, Chondrococcus blasticus and Mrjxococcus xanthus 

 gave typical carotin reactions in concentrated sulfuric acid, but were insoluble in 

 chloroform, ether, acetone and methyl and ethyl alcohol. An atypical carotin reaction 

 resulted with hydrochloric and nitric acids. He concluded the pigments to be 

 related to the carotins. 



The fruiting bodies. After growth as a vegetative colony the pseudoplasmodium 

 usually forms fruiting bodies which may in the different species be of many shapes and 

 sizes. Differentiation of species, genera and families is based almost entirely upon 

 the character of fruiting body developed. In some cases a stalk is produced, in 

 some not. 



In some forms the stalk is delicate and white, consisting of little-changed slime, in 

 other cases it may be stiff and colored. The rods evidently are carried up by the 

 slime which they secrete. In some forms the stalk is simple and short, in others 

 relatively long and branched. 



The rods ordinarily associate in more or less definite clumps to form cysts. These 

 cysts may be sessile or stalked. Usually the rods shorten and thicken materially 

 before the cyst ripens. In some forms they shorten so much as to become short ovoid 

 or cylindrical, functioning as spores. They are not endospores such as are found in 

 the genus Bacillus. 



The cysts may or may not possess a definite membrane produced from slime. Usu- 

 ally the cysts are bright colored, frequently red, orange or yellow. The spores within 

 the cysts when dried retain their vitality for considerable periods of time. Jahn 

 records germination of Polyangium fuscum after 5f years, of Myxococcus fulvus after 

 8 years. 



Methods of isolation. One technic of isolation used by the Krzemieniewskis 

 (1927, loc. cit.) was to sieve the fresh soil, place it on blotting paper in petri dishes, 

 and add sterilized rabbit dung. The soil was saturated with water to 70 to 100 per 

 cent, and the plates incubated at 26° to 30°C. After 5 to 10 days fruiting bodies began 

 to appear on the dung. Numerous species were isolated by this method. 



Mishustin (loc. cit.) employed silica gel plates on the surface of which sterilized 

 filter paper had been placed. Small lumps of soil were placed on the filter paper and 

 the plates incubated for several days at various temperatures. Vegetative myxo- 



