ISOLATION OF CELLULOSE BACTERIA 77 



Exercise 4 



. 



Fermentation of Cellulose by Denitrifying Bacteria 



1. Fill completely two Erlenmeyer flasks of 2oo-c.c. 

 capacity each with medium 37. 



2. Inoculate as follows: 



(a) i c.c. of a rich sewage suspension. 

 (&) i gram of garden soil. 



3. Incubate at 35 C. in a pan or plate so arranged as to 

 catch the overflow from the flasks. After one week the 

 cultures should begin to show fermentation, and by the 

 end of the second or third week all nitrates should be de- 

 stroyed. 



4. When the solution no longer reacts for nitrates pour 

 the turbid liquid off without removing the paper. Refill 

 the flask with the same medium minus the paper. Now 

 the process should proceed very much faster than in the 

 case of the first inoculation. 



5. The addition of new culture-media may be repeated 

 several times. 



Exercise 5 



Isolation of Cellulose Bacteria 



A. Without Enrichment Cultures: 



1. Dilute samples of soil in such a way that plates may 

 be made representing various dilutions, about i : 10,000 

 and i : 100,000 of a gram of the original material. 



2. Garden, field, and marsh soil should be used. 



3. Plate all of these inocula with medium 52. 



B. With Enrichment Cultures: 



i. At the same time plates are poured for A make 

 transfers from the enrichment culture, Exercise i, in sterile 

 99-c.c. water blanks. 



