96 LABORATORY BACTERIOLOGY 



EXERCISE XXXIX 



CULTURES OF ANAEROBIC BACTERIA 



139. 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 natural gas such as hydrogen. While certain 

 bacteria, like those of symptomatic anthrax, tetanus, and malig- 

 nant oedema, require the absence of oxygen, others, like Bacil- 

 lus subtilis, will not multiply without it. There are, however, 

 a large number of bacteria which are able to multiply independ- 

 ently 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. 



REFERENCES. See text-books on bacteriology. Hunziker, Jour, 

 of Applied Microscopy, Vol. V, No. 3. Gould, Annals of Surgery, 

 October, 1903. 



140. Work for this exercise. Examine and carefully de- 

 scribe the appearance of the anaerobic cultures made in Exer- 

 cise XXXVIII. 



With the wire loop remove one of the colonies from the 

 depth of the agar culture and examine it microscopically (i) 

 in a hanging-drop preparation and (2) in a stained cover-glass 



