7() 



NATURE, FORMATION, AND ACTIVITIES 



XOVOBIOCIN 



This antibiotic consists of three distinct 

 moieties: a sugar, substituted coumarin, 

 and substituted benzoic acid {Yau Tam- 

 elen, 1958). The addition of the last to the 

 medium i-esulted in an increase in the yield 

 of novobiocin, a fact which suggests the 

 precursory nature of the acid (Jones, 1958). 



Conclusions 



Examination of the chemical structure of 

 a large number of antibiotic complexes led 

 Abraham and Xewton (1958) to conclude 

 that many antibiotics are built up from 

 substances that play an essential metalxjlic 

 or structural role in the life of microor- 

 ganisms. Certain types of structure, such as 

 the large lactone or peptide ring, frequently 

 recur. This was believed to be a reflexion of 

 specific types of organization in microbial 

 cells. These workers emphasized that differ- 

 ent members of the same type of antibiotic 

 may be produced by such processes as N-, 

 0-, and C-methylation, X-acylation, and 

 the introduction of hydroxyl groups, or by 

 the substitution of one structural unit for 

 another of a similar type. The yield of a 

 given antibiotic can vary enormously with 

 changes in the concentrations of intermedi- 

 ates which accompany changes in cultural 

 conditions; modifications of the enzymatic 



systems which are a consequence of muta- 

 tions were also believed to play a role. 



Abraham (1959) made a detailed analysis 

 of the phenomenon of biogenesis of anti- 

 biotics. According to him, "What we now 

 know, and can reasonably surmise, about 

 the origin of the antibiotics points to the 

 economy with which their novel and some- 

 times intricate structures are made. Amino 

 acids and acetate, which feature as common 

 structural units, have widespread functions 

 in cellular metabolism. The condensation of 

 acetate, as acetyl coenzyme A, to yield a 

 /3-keto acid, and of activated amino acids 

 to form peptide chains, are familiar proc- 

 esses. So, too, is the transfer of a methyl 

 group from S-adenosyl-methionine to nitro- 

 gen, oxygen, or carbon in another molecule. 

 D-amino acids are commonl}' present in the 

 cell walls of bacteria and actinomycetes, 

 though they have not been detected in other 

 forms of life. Large peptide and lactone rings, 

 of a type previously unknown in natural 

 products, have now been identified so often 

 in the structures of antibiotics that their 

 formatiori would seem to have a broad 

 significance." He concluded that the bio- 

 synthesis and mode of action of antibiotics 

 might "be expected to illustrate the diversity 

 rather than the unity of nature." He added, 

 however, that this is only partly true. 



