OUTLOOK FOR THE FUTURE 319 



Isolation of antagonistic organisms from soils, coTufosts, manures, and 

 sewage 



a. Common agar media; colonies Isolated at random from plates 



b. Washed agar-bacterial media; zone-forming or other colonies se- 



lected 



c. Low dilutions; colonies producing inhibition of other organisms 



selected 



d. Special selective media 



Testing of isolated colonies 



a. Streak method; tested against gram-positive and gram-negative bac- 



teria 



b. Agar plugs removed from plates in which antagonist is growing 



c. Liquid media containing bacterial suspension inoculated with an- 



tagonist 



d. Agar media inoculated with test culture, followed by inoculation 



with antagonist 



Production of antibiotic substances 



a. Synthetic and organic media used 



b. Filtrate tested by convenient method 



c. Study of surface vs. submerged culture 



D etermination of antibacterial sfectruTn and general -prefer ties of 

 tyfe substance -produced 



a. Bacteriostatic spectrum by suitable methods 



b. Chemical and physical properties of crude preparation 



c. Pharmacological properties and in vivo activity 



Recognition of type substance on basis of antibacterial properties 



a. Bacteria: pyocyanase, pyocyanin, tyrothrlcin, and subtilin types 



b. Fungi: penicillin, gliotoxln, clavacin, and peniclllic acid types 



c. Actinomycetes: actlnomycetin, actinomycin, streptothricin, and 



streptomycin types 



Isolation of antibiotic substance 



a. By use of organic solvents 



b. By adsorption on charcoal, and removal by acid solutions or sol- 



vents 



c. Other methods 



Isolated antibiotics 



a. Antibacterial, physical, chemical, and pharmacological properties 



Chemother apeutic uses 



Figure 34. Isolation and preparation of antibiotic substances. 



