Bacillus Acidi Lactici, Hueppe. 



Origin. — It was obtained from sour milk. 



Form. — Short, thick rods, two to three times as long 

 as wide; these are usually in pairs; rarely in chains or 

 threads. 



Motility. — No real motion. Marked Brownian move- 

 ment. 



SP0RULA.TI0N. — Round, terminal bodies have been ob- 

 served, but these are not spores. 



Anilin dyes. — It stains readily; also by Gram's method. 



Growth. — Abundant and rapid. 



Gelatin plates. — The deep colonies are round or oval, yellow, sharp 

 bordered, finely granular. The surface colonies spread, forming thin 

 plaques, with irregular, wavy borders. The outer zone of the colony 

 is at first almost transparent and shows markings resembling the ven- 

 ation of leaves. 



Stab culture. — Slight growth along the puncture, but on the surface 

 it is considerable and spreads rapidly as a thin, dry, pearly-white cov- 

 ering. In old cultures bundles of crystals form along the line of inoc- 

 ulation, especially at or near the surface. 



Streak culture. — On agar, it forms a grayish white, moist, spreading 

 growth, which offers no special characteristics. On potato, it forms 

 a brownish yellow, slimy covering. 



Milk. — In sterilized milk it converts the lactose or milk-sugar, in 

 part, into lactic and carbonic acids. The acid reaction thus produced 

 causes a precipitation of the casein or curd. This change occurs only 

 in the presence of air. Old cultures do not alter milk — attenuation. 



Oxygen requirements. — It is a facultative anaerobe. 



Temperature. — It grows between 10° and 45°. The op- 

 timum is at about 30°. 



Behavior to gelatin. — The latter is not liquefied. 



Aerogenesis. — Gas is produced in milk. Carbon diox- 

 ide and alcohol are formed. 



Pathogenesis. — No effect. 0.75 per cent, lactic acid 

 stops the growth. Production of lactic acid in the mouth 

 (dental caries); abnormal fermentations in the stomach, 

 in the intestines. Lactic acid bacteria favor the growth of 

 anaerobic bacteria (see p. 100). 



The cultural characteristics resemble those of certain colon 

 bacilli and it may, therefore, be regarded as a variety of the B. 

 aerogenes. It may be considered as a common cause of the souring 

 ■of milk, but the production of lactic acid is common to a large number 

 -of bacteria, and hence, such organisms will also coagulate milk. 



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