BACTERIA CAUSING FERMENTATION 221 



BACILLUS ACETICUS PETERSII. 



Found in old sour dough ; resembles the Bacillus aceticus of Hansen. 

 Forms threads ; is strongly aerobic ; on gelatine slimy colonies develop. 



Bacteria causing Butyric Acid Fermentation. 

 BACILLUS BUTYRICUS (BOTKIN). 



Found in water, milk, and manured earth. 



Microscopical Appearances. Long motile bacilli, forming threads. 



Spore Formation present, situated in the middle of the rods, very 

 resistant, and are not killed during the process of sterilizing milk. As 

 they do not germinate under 18 C., milk sterilized for children should 

 be kept at a lower temperature before use. 



Staining Reactions. Stains by the Gram method. 



Biological Characters. Anaerobic. 



On Gelatine. Plates. Round or oval liquefying colonies, developing an 

 odourless gas. 



In Milk at the bottom of the culture a layer of serum forms, out of 

 which the gas rises upwards ; the milk is coagulated. The coagulated 

 albumen rises to the surface and is peptonised, so that eventually only 

 the fat swims on the surface. Butyric and allied fatty acids are formed. 

 In media containing sugar involution forms of the bacilli occur. 



BACILLUS BUTYRICUS (PRAZMOSKI). 



(Clostridium Butyricum.) 



Found in putrid vegetable infusions. 



Microscopical Appearances. Strongly motile bacilli, about 1 //. 

 broad, of various length, forming threads. 



Spore Formation present, situated in the middle of the rod, 

 causing a spindle-formed swelling. The spores are 1 //, broad and 2 to 

 2'5 fjb long. When the mature spore germinates the germinating rod 

 escapes at one end, while the spore membrane remains attached at the 

 other parts of the young bacillus like a cap. 



Staining Reactions. With a watery solution of iodine the bacilli, 

 when cultivated on media containing starch, are stained blue, whereby it 

 is called ' The Bacillus Amylobacter' 



