AEROBIC SPORE-BEARING NON-PATHOGENIC BACTERIA 509 



but has the same morphology and m many respects the same 

 reactions on media, as Bacillus cereus. It has therefore been 

 described as a fluorescent variety of this organism. 



Morphology. In young cultures on plain agar (6 to 20 hours) 

 the vegetative rods have rounded ends, slightly granular proto- 

 plasm and measure 0.5 to 0.75 by 1.5 to 4 microns. They fre- 

 quently grow in short chains. On glucose agar they are slightly 

 thicker and longer measuring 0.75 to 0.875 by 2 to 5 microns. 

 As the organisms mature they show many globular bodies in 

 their protoplasm which take the stain with difficulty. These are 

 particularly abundant on glucose agar. (Figures 68, 69, and 70.) 



Motility. Active motility in young cultures. 



Staining properties. Gram-positive. 



Spore formation. Spores begin to form early appearing in 24 

 hours on plain and on glucose agar. They are located in the 

 center or towards one end of the vegetative rods which swell 

 noticeably on sporulation. As the spores mature the protoplasm 

 disintegrates but remains attached to the spore, sometimes in 

 equal quantities at the ends and sometimes in greater amount at 

 one end than at the other. The spores thus resemble mesenteri- 

 cus spores but are much larger. The free spores measure 0.5 

 to 0.75 by 0.75 to 1.5 microns. They frequently remain attached 

 to each other in long chains. 



Agar slant. The growth is profuse, smooth, moist, and dull. 

 There is a definite ridge along the line of inoculation and the 

 edges are thin and sHghtly serrated. A yellow-green pigment is 

 diffused throughout the entire medium. This remains perma- 

 nently and increases with age. The pigment is especially pro- 

 nounced in an acid medium. Rarely there is considerable 

 wrinkhng and the formation of rather coarse folds. 



Agar stab. Shght granular growth along the fine of stab with 

 the gradual appearance of the characteristic pigment. 



Agar colonies. Irregular colonies which have a great tend- 

 ency to spread in amoeboid fashion. They are ghstening, 

 slightly translucent and shghtly raised. They become more 

 dense and dull as growth progresses and assume a greenish-yel- 

 low coloration. The colonies can be scraped off and are of a 



