220 SPECIAL BACTERIOLOGY 



On Agar a dirty white, ropy, slimy coating develops. 

 Milk at ordinary temperature in five to ten days becomes ropy, and 

 finally transparent, from disintegration of the milk globules. 



BACTERIUM ACIDI LACTICI (PETERS). 



Found in sour dough. Short motile rods, 0'4 to 1'5 p. 



Biological Characters. On Gelatine Plates round colonies with 

 concentric stratification of a light red colour. In solutions of sugar, to 

 which some yeast is added, this organism produces great quantities of 

 lactic acid. 



Bacteria causing Acetic Acid Fermentation. 

 BACILLUS ACETICUS (HANSEN). 



(Mycoderma Aceti.) 



The Mycoderma aceti was considered by Pasteur to be the cause 

 of the acetic acid fermentation in wine and beer. (Hansen divides it 

 into two forms, Bacillus aceticus and Pasteurianus.) 



Microscopical Appearance. Short, non-motile bacilli, forming 

 threads and frequently involution forms. 



Spore Formation absent. 



Staining Reactions. Stains by the Gram method. 



Biological Characters. Aerobic ; optimum temperature, 30 to 

 40 C. 



On Solid Media it grows on the surface, forming porcelain cup- 

 like colonies, especially on Beer Gelatine ; prepared by adding 5 per cent, 

 gelatine to beer. 



In Liquid Media a membrane forms on the surface, the underlying 

 liquid being slightly clouded. 



Specific Actions. It oxidises alcohol, forming acetic acid, and further 

 splitting up the latter into CO 2 and H 2 O. It is distinguished from other 

 members of the group by staining yellow when treated with a solution 

 of iodine. 



BACILLUS PASTEURIANUS (HANSEN). 



(Mycoderma Pasteurianum). 



This bacillus is found in beer and wine, but does not occur as 

 frequently as the previous organism, from which it is distinguished by 

 giving a blue reaction with solution of iodine. 



