Introduction 



particularly prolific source of organisms adaptable to antibiotics 

 production when grown in suitable media. 



Research with the actinomycetes resulted in the discovery of 

 agents effective against a broad spectrum of pathogens. The 

 first of these were chloramphenicol, chlortetracycline and oxy- 

 tetracycline. Since the discovery of oxy tetracycline, no anti- 

 biotics of broader antibacterial range have been developed. 



Prior to the discovery of antibiotics, much work had been 

 done on the structures of lichen substances, and, as mentioned 

 above, a few academic laboratories were interested in mold 

 metabolites. Notable among these was Professor Harold 

 Raistrick's group at the London School of Hygiene and Tropical 

 Medicine. Raistrick, now retired, and his collaborators have 

 published over 100 papers on this topic. 



The academic investigators were impelled by no practical 

 motive except perhaps a hope that comparison of the chemical 

 metabolites of various ill-defined groups of fungi would assist 

 in their classification. Some generalizations did become ap- 

 parent, but on the whole this hope was disappointed. It was 

 found that the same chemical might even be produced by both 

 bacteria and fungi. Some of the old classification schemes 

 based on pigmentation were found to be obsolete. 



The structures of the large molecules produced by micro- 

 organisms have proved to be more specific and of real value to 

 taxonomy. Since the advent of paper chromatography, the 

 identification of amino acids, sugars and other fragments from 

 cell tissue hydrolysates has been facilitated. From the ensuing 

 proliferation of literature on this subject it is manifest that the 

 compositions of various cell tissues (capsule, wall, protoplast 

 membrane, internal proteins), as well as exotoxins and other 

 high molecular weight exudates, are much more specific. Even 

 strains of species can sometimes be distinguished by the pres- 

 ence or absence of one of these fragments, and these molecules 

 are important in immunology. Work of this sort has become 

 more important since the discovery of evidence that certain 

 antibiotics, e.g., penicillin, interrupt growth and cell division in 

 the bacteria against which they are effective by interfering with 



