1222 



Use of the milkmould for the pure culture of anaerobes. 



In nature the withdrawing of oxjgeri from the environment, which 

 is required for the development of anaerobes, is iisuallj caused h'^ 

 aerobic microbes. 



They not only absorb the last traces of oxygen from the sur- 

 roundings but even produce reducing substances in it. In the labora- 

 tory this may be imitated by adding to a culture medium containing 

 in small number germs of the anaërobe to be examined, a great 

 number of germs of an appropriate aerobic microbe. How such expe- 

 riments have hitherto been carried out ^) may be illustrated by a definite 

 example namely the cultivation of the si)ore-forming aerobes of the 

 albumin putrefaction; then I will describe the modified method. 



A crude culture of puti-efaction bacteiia is obtained thus. A stop- 

 pered bottle is quite filled with a watery infusion of albuminous 

 matter, infected with gaiden soil and boiled to kill all non-sporo- 

 genous microbes. Placed in the incubator the mass soon passes into 

 stinking putrefaction, characteristic by the presence of mercaptans 

 produced by the spore-foiining anaerobes. Now to ordinary broth-gelatin 

 or broth-agar an abundant quantity of some intensively growing 

 aerobic bacterium, such as B. fiuorescens or B. prodigiosiim is aóóeó, 

 together with a little of the to 90^ or 100^ 0. heated material 

 containing the spores of the putrefaction microbes. After solidification 

 in a test tube the aerobes near the bottom will soon absorb the 

 last traces of oxygen and being unable to grow there, not give rise 

 to liquefaction of the gelatin ; but they will retain the oxygen pene- 

 trating from above and develop strongly in the surface of the gelatin. 

 In the lower part of the tube the spores of the putrefaction bacteria 

 can now germinate and if gelatin is used there will soon appear the 

 large liquefying colonies of the so remarkable Bacillus septicus, together 

 with the non-liquefying putrefiers, for the greater pai't recognisable by the 

 flocculent structure of their colonies, a character related to their 

 sensitiveness to extension and contraction of the substratum where- 

 in they grow, quite as by B. Zopfii. For the microscopical exami- 

 nation this method undoubtedly affords good material, but it is 

 hardly possible to reach the single anaerobic colonies without 

 touching others. To this end it is necessary to remove the 

 culture gelatin from the tube by heating it in the flame so that only 

 the outer side of the gelatin melts and the contents may be thrown 



1) E. Mace, Traite pratique de Bacteriologie, 6e Ed. T. 1, pag. 305, Paris 1912. 

 Besson, Technique microbiologique et sérolhérapique, 6e Ed., pag. 102, Paris 1914. 



