72 A MANUAL OF BACTERIOLOGY 



5. Partial reduction is indicated by the formation of a dark 

 color due to the formation of ferrous sulphide. Pour a portion 

 of a culture into a test tube and test for sulphates with barium 

 chloride. Test the controls for the relative amount of sulphates. 



Exercise 104. The Cultivation of Bacillus amylobacter 



The group of organisrhs represented by B. amylobacter lives 

 upon starchy material and effects its decomposition. 



1. Cut slices of beets and place them in wide-mouthed bottles 

 or flasks of 50 cc. capacity. Pour in tap water until the flasks 

 are full and close them with rubber stoppers. If beets are not 

 obtainable, a substitute may be had in thick starch prepared as 

 follows: Boil 100 cc. of distilled water until air is expelled; re- 

 move the flame and stir in coarsely ground rice until the paste 

 is thick enough to support a spoon in a vertical position ; add a 

 few grams of wheat starch and stir it in. 



2. Keep the material at 35°- 37° C. for twelve to forty-eight 

 hours. 



3. After fermentation is apparent, transfer a drop of paste to 

 a drop of Gram's iodine solution. 



4. Examine the preparation for spindle-shaped bacteria contain- 

 ing granules. 



Exercise 105. Study of Bacillus mycoides 



This organism represents those soil organisms which play an 

 important part in ammonification. 



Make stains of B. mycoides, using carbol-fuchsin and Gram's 

 method. Using material from an old culture, make a spore stain. 

 Make cultures on agar plates, agar slope, gelatin stab, and potato. 

 Grow the organism on ordinary bouillon or on Dunham's solu- 

 tion, and test for ammonia. 



Exercise 106. Study of Bacillus vulgatus {Bacillus mesentericus 

 vulgatus Fliigge) 



This is the organism commonly known as potato bacillus. It 

 is common in soils and hence is a frequent contamination of 

 our potato cultures. In incompletely sterilized milk it some- 

 times causes slow curdling. Later the curd is digested, with the 

 formation of bitter substances. 



