1 62 BACTERIA 



white crumbly deposit forms in the bottom of the stab. On agar 

 plates it produces yellowish-white colonies, surrounded by a zone 

 of bluish-green fluorescence. It grows luxuriantly. In agar tubes 

 it multiplies rapidly, spreading over the medium, with wavy thick- 

 ened edges. The agar quickly turns a dark greenish-blue, and 

 in old cultures the growth changes from yellow to greenish-blue. 



FIG. 53. Bacillus pyocyaneus. (Kolle and Wassermann.) 



In bouillon it is very dense and yellowish-green; a pellicle forms 

 on the surface, and a sediment is deposited. In old bouillon cul- 

 tures the bacilli undergo autolysis and disappear. In milk the 

 growth is luxuriant, the casein is coagulated, and the clot is ulti- 

 mately digested. The reaction is alkaline. On potato it varies 

 in luxuriance, often being slightly elevated, yellowish, turning to 

 green. The variance in growth is due to the kind of potato used. 

 Drying kills the organism speedily; four hours in sunlight also de- 

 stroys it. 



Chemical Activities. No gas is generated. Besides the pig- 

 ments (already specified) ammonia is produced, also a peculiar 

 enzyme called pyocyanase by Emmerich and Lowe, which not only 

 digests gelatine and milk-curd, but its own and other bacterial cells 



