CHAPTER VI. 



STUDY AND IDENTIFICATION OF BACTERIA. SPORE- 

 BEARING BACILLI. KEY AND NOTES. 



A. Grow aerobically. 



1. Stab culture in gelatin has branches growing out at right angles to line 

 of stab. 



a. Has no membrane on bouillon or liquefied gelatin. Projecting 

 branches from line of stab only at upper part of line of growth. 

 Absolutely nonmotile. Ends sharply cut across or concave. 

 ANTHRAX GROUP. 



b. Has thick whitish membrane on bouillon and surface of liquefied 

 gelatin! Projecting branches all along the line of stab. Sluggishly 

 motile. MYCOIDES GROUP. (B. mycoides. B. ramosus.) 



2. Stab cultures in gelatin do not show projecting branches. 



a. Potato cultures do not become wrinkled. At first slightly moist, 

 later dry and mealy. SUBTILIS GROUP. (Hay bacillus group.) 

 Actively motile. 



The yellow subtilis is at times found in water. The colonies on 

 potato are of a cheese-yellow color. The bacilli are very large and 

 show a slugglish, worm-like motion. 



b. Potato cultures become wrinkled. VULGATUS GROUP. 

 (Potato bacillus.) 



Two water bacilli belonging to this group are the B. mesentericus 

 fuscus (brown growth) and B. mesentericus ruber (red growth). 



NOTE. The following cultural characteristics are common to all the above 



spore bearers. 



1. Liquefaction of gelatin. 



2. Milk slowly coagulated with very little change in reaction. Later the 

 coagulum is digested. 



3. No gas in either glucose or lactose. 



4. No indol. 



5. All are Gram positive. 



6. All digest blood-serum. 



B. Grow only anaerobically. 



1. Rods very little swollen by centrally situated spores. 



a. Motile. B. cedematis maligni. (Gram negative.) 



b. Nonmotile. B. aerogenes capsulatus. (Capsule.) 



2. Spores tend to be situated between center and end. 



a. No liquefaction of gelatin. B. butyricus. 



b. Gelatin liquefied slowly. 



B. botulinus. Milk not coagulated. 



B. anthracis symptomatici. 



B. enteritidis sporogenes. Milk coagulated with abundant gas. 



c. Gelatin liquefied rapidly. B. cadaveris sporogenes. Very motile. 



3. Spores situated at end of rod. Drum-stick sporulation. TETANUS 

 GROUP. 



53 



