j{i(>('iii:Mi('AL A("i'i\i'ni;s 



163 



Tahi.k 40 

 Composition of cell walls of some (jram-posilivc Eiibucleriulcs and AcliiwmyccLalcii (Work) 



* DAP = diaminopimelic acid; Gly = glycine; Asp = aspartic acid; Ser = serine; Glue = glucose; 



Gal = galactose; Man = mannose; Arab = arabinose. 

 t Muramic acid = 3-()-a:-carboxvcthvl hexosamine. 



The presence of nucleic acids and phos- 

 phorus ill the mycehum of actinomycetes has 

 been studied by Guberniev et al. The abihty 

 of actinomycetes to synthesize poly lae vans 

 was studied by 0rsko\' and Veibel (1938). 



Amino Acid Synthesis 



Various actinomycetes have been found 

 capable of liberating;? certain amino acids in 

 synthetic media in which they ha\-e grown. 

 Among these acids glutamic acid occupies a 

 prominent place. The maximum concentra- 

 tion of this acid was found by Perlman and 

 O'Brien to range from 0.25 to 1.75 gn\/\, cor- 

 responding to a conversion of 4 to 29 per 

 cent of the nitrogen in the medium. The 

 presence of glutamic and other amino acids 

 in the extracellular fluids of different sp(>('i(>s 

 oi Strcptomyces was belie\'ed to be due to the 

 autolysis of the cells of the organisms (Gil- 

 mour et al. 



Antibiotic Biosynthesis 



Antibiotic biosynthesis has contributed 

 much to our knowledge of the chtMuical 

 structure of the actinomycete cell. A sub- 

 .stantial (juantity of streptonwcin has been 



found to occur bound to the cells of the or- 

 ganisms, suggesting that the antibiotic may 

 be a part of the cell wall of the organisms 

 producing it. The bound streptomycin may 

 be released by treatment of the mycelium 

 with acids, with alkalies, or with ionizable 

 salts, but not by the disintegration of the 

 cell by sonic energy, bacteriophage, or en- 

 zymatic treatment, as pointed out in Chap- 

 ter 11. This is true also of the antibiotics 

 streptothricin, neomycin, chloramphenicol, 

 and the tetracyclines. This binding of the 

 antibiotic to the cell does not appear to be a 

 simple ion-exchange phenomenon, since 

 streptomycin added to the mycelium of S. 

 griseus was not adsorbed; the binding power 

 of the mycelium is apparently not a function 

 of its weight. Some of the antibiotics, notably 

 the basic compounds, may be considered as 

 polysaccharides, perhaps related to the cell- 

 wall polysaccharides of microorganisms. 

 Other antibiotics, .such as chloramphenicol 

 and the actinomycins, may be considered as 

 polypeptides. 



These facts do not explain the mode of 

 action of antibiotics upon l)a('teria and other 

 microorganisms. The sensiti\-itv of actino- 



