AEROBIC SPORE-BEARING NON-PATHOGENIC BACTERIA 521 



MoUlity. Active and progressive rotatory motiUty in 24 hour 

 agar cultures. 



Staining properties. Gram-negative. 



Spore formation. Spores are formed early often withm 24 hours 

 on both plain and glucose agar. They are round, and usually ap- 

 pear at the ends of the organisms m a sub-termmal position, but 

 may be distmctly terminal. The spores are of greater diameter 

 than the vegetative rods from which they spring and thus give a 

 clavate or club-shaped appearance to the organisms. The organ- 

 isms taken from glucose agar resemble markedly the tetanus baci - 

 lus cultivated on this medium. The free spores retam fauly thick 

 waUs of protoplasm for some time. They vary m size from 1 to 

 1.125 microns in diameter. 



Agar slant. Moist rather thin translucent growth m 24 hours, 

 becoming pale yellowish white in old cultures. No tendency to 

 spread except when the medium is very moist. 



Agar stah. Faint growth along Ime of inoculation with shght 

 spreadmg on the surface. In older cultures the surface growth is 

 thicker and more abundant but does not usuaUy spread far from 

 the line of puncture. Easily scraped from medium. 



Agar colonies. Colonies round and regular or amoeboid m 24 

 hours Under low power they show dark central areas with Ughter 

 peripheries. As they age they become thicker and denser with 

 more pronounced central nuclei. 



Gliu^ose agar. Pale white moist rather thin growth in 24 hours, 

 becoming pale yellow or cream yellow in older cultures. 



Glucose agar colonies. In 24 hour plates the colomes are nregu- 

 lar, amoeboid, thick, sho^ving under low power darker central nu- 

 clei with lighter peripheries but with entire edges. As the colomes 

 become older they become denser and thicker with heaped-up 

 edges They give a pecuUar bizarre appearance to the plate as 

 though it was covered with drops of moisture. Reaction of agar 

 remains neutral or becomes alkahne. . 



Gelatin stab. Faint Une growth appearing after 48 to 72 hours 

 with a sUghtly spreading growth on the surface. In older cultures 

 the surface growth spreads considerably from the point of puncture 

 on top of the gelatin which remains soUd. Rarely the Une growth 

 becomes arborescent. 



