CHAPTER III 



CULTURE MEDIA, THEIR PREPARATION AND 

 STERILIZATION 



Probably the oldest methods of cultivating fungi were developed in grow- 

 ing the common mushroom of commerce {Psalliota campestris and related 

 species), but these methods had little, if any, influence on the scientific study 

 and cultivation of fungi. Undoubtedly many mycologists of the nineteenth 

 century brought into their laboratories young fructifications attached to their 

 substrate, and watched their development, also making many important ob- 

 servations on material of early stages collected in the field. It remained, how- 

 ever, for Pasteur and Koch in the decade 1873-1883 to develop methods of 

 sterilization, isolation, and pure culture of bacteria to pave the way for our 

 present technique. Earlier authors in several instances had anticipated these 

 methods more or less completely, but their accounts had either been forgotten, 

 buried under the debris of the theory of spontaneous generation, or lost in a 

 little-known periodical of very limited circulation ; e.g., the work of Bizio 

 on Serratia marcescens (Bacillus prodigiosus) which was published in 1823 and 

 was only generally known among scientists after its translation and publication 

 in 1924. For a more complete account of the historj^ of bacteriologic methods 

 the reader is referred to the excellent short account in Conn & Conn's Bac- 

 teriology and, for formulae of the media used to Desgardes (1921) and to 

 Levine and Schoenlein (1930). 



In all work with pure cultures it is essential that everything used should 

 be clean and sterile. This statement seems so axiomatic to the well-trained 

 medical man that its emphasis here may appear out of place, but in this gen- 

 eration when so much routine work is left to technicians and even humbler 

 laboratory folk, it may not be out of place. Also in my classes I frequently 

 find students with so little previous training in bacteriology that in the fol- 

 lowing pages I shall not assume any previous experience in handling micro- 

 organisms in pure culture. 



The cleaning of glassware, while one of the drudgeries of the laboratory, 

 is very important.* Needless to say the glassware should be washed with 

 soap and water until clean tap water will drain freely from it, and not hang 

 in drops over the sides of test tubes, etc. This stage may be called physically 

 clean. We must then be sure that it is chemically clean, i.e., that it does not 

 contain any substances, minute traces of which may inhibit or cause abnormal 

 growth of the organism to be cultivated. 



♦If the glassware has been used for cultures, it should be sterilized by autoclaving (see 

 pp. 47, 48) before proceeding' to wash it. Pautrier and Rietmann (1924) report infection of a 

 laboratory worker with Trichophyton granulosum (ordinarily confined to horses) while clean- 

 ing tubes containing year-old cultures ! 



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