PART II 

 SPECIAL BACTERIOLOGY 



CHAPTER XVI 

 SOME COMMON BACTERIA SLIGHTLY PATHOGENIC 



Bacterium Prodigiosum (Ehrenberg). This bacillus, 

 formerly called micrococcus, is very common, and was one of 

 the first noticed, because of the brilliant red pigment it 

 forms on cooked vegetables and starchy substances. "The 

 bleeding host" miracles are said to have been due to it. 



Morphology. Short rods, often in filaments, resembling 

 cocci, ends slightly pointed, i ju in size ; spores absent. 



Facultative anaerobic, that is, it can grow without air; but 

 the pigment requires oxygen for its development. 



Flagella and motion present in young bouillon cultures. 

 Absent in older and those grown on potato. 



Stain easily with ordinary watery stains, but not with 

 Gram. 



Cultural Features. A gar stroke: Growth limited to stroke; 

 filiform, varying from a light pink to dark purple in color, 

 due to pigment (prodigiosin) formed by the growing colcnies. 

 Odor of trimethylamin present. Media colored brown under- 

 neath growth. 



On potato, growth of pigment appears best. At first rose 

 red, then in a few days dark purple, with a glistening, green- 

 gold luster, resembling the dry fuchsin dye. Odor more 

 pronounced. 



Gelatin Stab. In six hours liquefaction begins on surface, 

 and spreading downward; funnel shape; the liquid portion 

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