BACTERIUM FBODIGIOSUM. 273 



Most Important Literature. — Scliottelius (C. B. II, 439); Wasserzug 

 (A. P., 1888); Kiibler (C. B. v, 383 ) ; Scheurlen (A. H. xxvi, 1). 



Microscopic Appearance. — From solid nutrient me- 

 dia, very short bacilli, often looking like cocci. The ends 

 are somewhat pointed or rounded. The greatest diameter 

 is 1 /i (21, XI ; 22, ix). In bouillon, especially if it is 

 faintly acid, there occur longer forms, distinct rods, and 

 shorter and longer threads. 



Motility.— In young bouillon cultures there is active 

 motion, produced by from 6 to 8 long, peritrichous flagella 

 (21, XII ; 22, xi). On the contrary, older agar and 

 potato cultures appear non-motile, and in them the bacil- 

 lus produces abundant slimy material, which limits mo- 

 tion. Scheurlen attributes the mucous formation to the 

 abundant production of alkali. 



Staining Properties. — Easily stained, but not by 

 Gram's method. 



Relation to Oxygen. — Facultative anaerobe; grows 

 better as an aerobe. Also as an anaerobe it liquefies gelatin 

 (also with the addition of 2 per cent, sugar), but forms 

 no pigment. 



Requirements as Regards Temperature and Com- 

 position of Nutrient Media. — Optimum at 22°-25° ; in 

 the incubator, especially at 38°-39°, the formation of pig- 

 ment is suspended. A more prolonged cultivation at a 

 higher temperature permanently lessens the formation of 

 pigment. ' It grows also, with production of pigment, 

 upon non-albuminous nutrient media. 



Gelatin Plate. — (a) Natural size: At first the super- 

 ficial colony is a grayish-white point, and the gelatin is 

 liquefied at once. The area of liquefaction is shaped like 

 a plate. The peripheral zone is lighter than the central 

 zone. Original colonies are often colored reddish, but often 



with the Bact. prodigiosum, since both are identical (compare p. 

 276). 



' It may be heie remarked that, without known cause, chromo- 

 genesis by the Bact. prodigiosum is often much reduced. As is often 

 seen, of 20 cultures made at the same time and from the same origi- 

 nals upon the same nutrient media, many form pigment abundantly 

 and others very feebly. Also, upon plates fainter and more deeply 

 colored colonies always occur side by side. 

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