ANTIBACTERIAL EFFECTS 131 



not characteristic of any one genus or even species, but of certain strains 

 within a given species. Different strains may produce distinct variants 

 of a given antibiotic. This is true especially of penicillin, of which a 

 number of types have now been isolated, varying both chemically and 

 in their selective antibacterial properties. 



Some organisms produce more than one antibiotic. Two genera, 

 Penicillium and As-pergillus, have been found to comprise a large num- 

 ber of antagonistic forms. Several other genera are also known to con- 

 tain organisms that possess antibacterial properties j very few of these, 

 however, were ever found among the Phycomycetes j the Basidiomy- 

 cetes also include a large number of organisms capable of producing 

 antibiotics. 



The active fungi may be divided (956) into the following eleven 

 groups: 



Asfergillus clavatus A. jumigatus 



A. flavus-oryzae PenictlliuTn cyclofium-clavijorine 



Penicillium luteum-furfurogenum Fusarium-C efhalosforium 



Penicillium notatum^-chrysogenum ChaetowJium, and other Ascomycetes 



Trichoderm.a-GVtocladium, Basidiom-ycetes 



Miscellaneous other fungi 



A comparative study of a number of fungi taken from a culture col- 

 lection brought out ( 1017) the fact that about 40 per cent of the Asper- 

 gilli {Aspergillus fumaricus, A. fumigatus, As-pergillus schiemannii, 

 Aspergillus terreus) and 1$ per cent of the Penicillia {Penicillium 

 chrysogenufHy Penicillium clavijorme, Penicillium funiculosum, Peni- 

 cillium exfansum) possessed antagonistic properties. In a study of lOO 

 strains of Aspergilli (1018), 28 were found to be active against S. au- 

 reus, 16 against E. coli, and 9 against Ps. aeruginosa; strains of ^. niger 

 were most positive and those of A . versicolor were negative. Among the 

 Penicillia, in addition to P. notatumy the following were shown ( lOio) 

 to produce considerable antibiotic action: P. brunneoviolaceumy P. 

 chloro-leucon, P. citrinum, P. chrysogenum, and P. griseo-roseum, the 

 last two species producing the penicillin-type of action. The composi- 

 tion of the medium and the nature of the strain are of great importance. 

 The active producers of antibiotic substances belong to the group of 



