706 MANUAL OF DETElliMINATIVE BACTP^RIOLOGY 



forming a pellicle on broth. Usually oxidize carbohydrates or proteins more or less 

 completely, often producing slight acidity, without pronounced accumulation of 

 characteristic products. Soil is the most common habitat. 



The internationally accepted (Jour. Bact., 33, 1937, 445) type species is Bacillus 

 subtilis Cohn emend. Prazmowski. 



Key to the species of genus Bacillus. 



I. Mesophilic (good growth at 30°C), aerobic (sometimes also grow at low concentra- 

 tions of oxygen). 



A. Spores ellipsoidal to cylindrical, central to terminal, walls thin. Sporangia 



not distinctly bulged. Gram-positive. 



1. Diameter of rods less than 0.9 micron. Cells from glucose or glycerol 



nutrient agar stain uniformly. 

 a. Growth at pH 6.0. Acetylmethylcarbinol produced. 



b. Gelatin hydrolyzed (Frazier method). Acid from xylose or arabi- 

 nose with ammoniacal nitrogen. 

 c. Starch hydrolyzed. Nitrites produced from nitrates. 



1. Bacillus subtilis. 



d. Black pigment on carbohydrate media only. 



la. Bacillus subtilis var. aterrimus. 

 dd. Black pigment on tyrosin media only. 



lb. Bacillus subtilis var. niger. 

 cc. Starch not hydrolyzed. Nitrites not formed from nitrates. 



2. Bacillus pumilus. 



bb. Gelatin not hydrolyzed. No acid from xylose or arabinose. 



3. Bacillus coagulans. 



aa. No growth at pH 6.0. Acetylmethylcarbinol not formed. 

 b. Casein digested. Urease not formed. 



4. Bacillus firmus. 

 bb. Casein not digested. Urease produced. 



5. Bacillus lentus. 



2. Diameter of rods 0.9 micron or more. Cells from glucose or glycerol 



nutrient agar appear vacuolated if lightly stained. 

 a. Acid from xylose or arabinose with ammoniacal nitrogen. Acetylmethyl- 

 carbinol not produced. 



6. Bacillus megatheriuvi. 



aa. No acid from xylose or arabinose. Acetylmethylcarbinol produced. 



b. Saprophytic, sometimes pathogenic but not causing anthrax ; usually 

 motile. 

 0. Growth on agar not rhizoid. 



7. Bacillus cereus. 



cc. Rhizoid growth on agar; usually non-motile. 



7a. Bacillus cereus var. mycoides. 

 bb. Pathogenic. Causative agent of anthrax; non-motile. 



8. Bacillus anthracis. 



B. Spores ellipsoidal, central to terminal, walls thick, remnants of sporangium 



often adhering. Sporangia distinctly bulged, spindle and racket forms. 

 Gram-variable. 

 1. Acid and gas from carbohydrates. 



a. Acetylmethylcarbinol produced. Crystalline dextrins not formed from 

 starch. 



