AEROBIC SPORE-BEARING NON-PATHOGENIC BACTERIA 313 



Morphology. Thick stubbed homogeneous organisms with 

 round or pointed ends usually appearing as single cells or in twos. 

 No chain formation. On 24 hour plain agar cultures they 

 measure 0.5 to 0.75 by 1.5 to 2 microns. Organisms not in- 

 creased in size on glucose agar and protoplasm remains homo- 

 geneous. Sometimes long forms 6 to 8 microns appear in old 

 cultures. (Figures 48, 49, 50 and 51.) 



Motility. Active progressive and rotatory motihty in 24 

 agar cultures. 



Staining properties. Gram-negative. 



Spore formation. Spores form early appearing in 24 hours on 

 both plain and glucose agar. They are round, greater in 

 diameter than the organisms from which they spring, and are 

 usually located at the ends of the rods in a terminal or sub- 

 terminal position. They thus give a clavate or club-shaped 

 appearance to the rods which resemble somewhat the tetanus 

 bacillus. The spores may also be central and the rods thus be- 

 come fusiform in shape. The free spores may retain spurs of 

 protoplasm assuming a peculiar diamond shape or may appear 

 naked. They vary in diameter from 0.5 to 1 micron and are 

 occasionally swoHen equaling 1.5 microns in thickness. 



Agar slant. Thick white rather dry growth in 24 hours, 

 becoming distinctly yellow or cream-colored in old cultures. 

 Easily scraped from medium. 



Agar stab. Faint line growth and non-spreading surface 

 growth. 



Agar colonies. Superficial colonies may be round, regular 

 thick and opaque, or thin and spreading. Under low power 

 they show dark central nuclei and thinner margins with clean- 

 cut edges. Older cultures thick and heaped up. Deep colonies 

 small and fine, under low power dark, opaque, round or irregular. 



Glucose agar. Thick dry growth with heaped-up edges be- 

 coming thicker and granular in old cultures. Reaction alkaline. 



Glucose agar colonies. Superficial colonies thick, irregular 

 spreading and heaped up. Under low power granular with 

 irregular fuzzy margins. Deep colonies opaque under low power 

 showing irregular fuzzy edges. Older colonies thicker and more 

 bizarre-shaped. Reaction alkaline. 



