CULTIVATION AND PRESERVATION OF PENICILLIA 85 



to recognize, hence the importance of exercising the greatest possible care 

 in the making of every transfer cannot be over emphasized. 



Contamination 



In routine laboratory work, strains of Penicillium may become con- 

 taminated with bacteria, yeasts, and actinomycetes unless proper safe- 

 guards are exercised. Such contaminated cultures may go unnoticed for 

 considerable periods of time if the substratum employed does not par- 

 ticularly favor the growth of the contaminant. Cultures can be readily 

 repurified as a rule by the techniques described under dilution and streak 

 cultures. 



Detection of contamination by actinomycetes may be unusually diffi- 

 cult, since a few species of Penicillium themselves produce an odor strik- 

 ingly like, or identical with, that produced by many actinomycetes. Peni- 

 cillium bif 07-7716 Thom is a case in point. Over a period of many years 

 Thorn unsuccessfully attempted to demonstrate the presence of an ac- 

 tinomycete which could account for its characteristic earthy odor. West- 

 ling and Biourge reported similar experiences. In this case it has been 

 shown beyond reasonable doubt that no foreign organism is present. In 

 other cases the development of similar odors undoubtedly results directly 

 from such contamination. The worker handling cultures of Penicillium 

 must, therefore, exercise every possible precaution and must in certain 

 cases repeatedly confirm the purity of his cultures. 



Cultures of Penicilliimi may become contaminated by molds of other 

 genera. Westling's culture of Penicilliimi haculatum, as received by Thom, 

 was found to contain a culture of Aspergillus repens, and it is believed 

 probable that the ascosporic stage which Westling (1910) described for 

 P. haculatum was based upon this Aspergillus. 



Hygiene 



The Penicillia are characterized by the production of tremendous 

 numbers of aerial spores or conidia, which are very small and very light. 

 They are carried about by the slightest air currents, hence tubes or plates 

 containing mature colonies should be open for the minimum time neces- 

 sary to effect reinoculations, and rough handling should be avoided al- 

 ways. Every possible precaution should be taken to work in an area where 

 the air is entirely quiescent. When large numbers of transfers are to be 

 made, a special inoculating room or culture chamber should be available, 

 and it is desirable that the walls should be finished in some material which 

 can be sponged with antiseptics or steamed out from time to time. Air 

 entering the room should be sterile (a convenient means of obtaining sterile 

 air is to force incoming air through appropriate paper or cloth filters that 



