132 FUNGI AS ANTAGONISTS 



Asymmetrica. Of many Phycomycetes tested, only Phythofhthora 

 erythroseftka showed some activity. A few Ascomycetes were also 

 found to be active. Next in importance to the Aspergilli and Penicillia 

 as producers of bacteriostatic substances are the Basidiomycetes. 



A summary of the antibacterial properties of various fungi and of 

 the antibiotic substances produced by them is given in Table 24. In ad- 

 dition to the specific strain of the organism, the composition of the me- 

 dium and the conditions of growth, especially aeration, are most im- 

 portant in controlling the amount and nature of the antibiotic substance 

 produced by the organism. Different strains of the same organism 

 when grown under identical conditions vary greatly in the production 

 of the antibiotic substance, as shown for A. clavatus (968) and other 

 fungi (497). 



PenicilUum notatum-chrysogenum Grouf 



Because of the production by these organisms of penicillin, which has 

 already found a wide practical application, this group of fungi deserves 

 special attention. Fleming (261) first observed that a fungus culture 

 growing on a staphylococcus plate brought about destruction of the bac- 

 teria, as shown by the fact that the colonies became transparent and 

 were undergoing lysis. The fungus was isolated in pure culture and was 

 later identified as P. notatum. It was found to possess marked bacterio- 

 static and bactericidal properties for some of the common pathogenic 

 bacteria, largely the gram-positive cocci and the staphylococci, the strep- 

 tococci, the diphtheria organism, and the gonococci and meningococci ; 

 bacteria belonging to the colon-typhoid-dysentery group were not af- 

 fected. The culture filtrate of the fungus was found to contain an active 

 substance, which was designated as penicillin. 



The selected culture of the fungus is grown on one of the media de- 

 scribed earlier (pp. 65-69). The reaction of the medium changes from 

 slight initial acidity (;)H 6 to 7) to distinct acidity (^H 3.0), followed 

 later by alkalinity, finally reaching a pH of 8.0 or even 8.8. A faint to 

 deep yellow color is produced in the medium. Penicillin production is 

 usually at its maximum at about /)H 7 and may remain constant for sev- 

 eral days or may fall again rapidly. In stationary cultures, once a fungus 

 pellicle has been produced, the medium can be replaced several times, 



