ANAEROBIC CULTURES 57 



EXERCISE XXII 



MAKING CULTURES OF ANAEROBIC BACTERIA 



87. Certain bacteria will not grow in the presence of oxy- 

 gen (atmosphere), and consequently they must be cultivated 

 in a medium from which the air has been expelled, or in the 

 presence of some neutral gas such as hydrogen. While cer- 

 tain bacteria, like those of symptomatic anthrax, tetanus, and 

 malignant oedema, require the absence of oxygen, others, like 

 Bacillus subtilis, will not multiply without it. There are, how- 

 ever, a large number of bacteria which are able to multiply 

 independently of the presence or absence of this element. 

 In reference to oxygen requirements bacteria are grouped as 

 follows : — 



Obligative aerobic bacteria require oxygen. 



Obligative anaerobic bacteria require the absence of 



oxygen. 



Facultative aerobic bacteria grow best in the absence 



of oxygen, but will grow in the presence of air. 



Facultative anaerobic bacteria grow best in the presence 



of oxygen, but will grow in its absence. 



There are several methods of cultivating anaerobic bacteria, 

 but as a rule they are difficult and cannot be easily handled in 

 an elementary course. Two of the simpler processes, however, 

 will be tried. 



88. Work for this Exercise. — Following the method of 

 Liborius for cultivating anaerobic bacteria, inoculate a tube 

 of agar from the culture furnished. 



Inoculate 2 fermentation tubes from the same culture. One 

 of the fermentation tubes should contain sugar-free bouillon 

 (furnished), the other bouillon containing 1% glucose. 



Inoculate for study at the next exercise 2 tubes of liquid 

 agar (one plain and one containing glucose), a fermentation 



