366 



METABOLISM OF MICROORGANISMS 



which give mainly streptomycin, and in high yields — about 2-3 g. per 

 liter of medium. This antibiotic is produced by many companies in the 

 United States and foreign countries. In 1952 the production in the 

 United States was 440,000 lb., and the market value at the plants was 

 about $50,000,000. 



Its use is attended with some drawbacks. The tubercle and other 

 bacteria become resistant to streptomycin. It also has toxic effects on 

 the eighth cranial nerve which may lead to deafness on prolonged use. 

 However, in spite of much effort, no other antibiotic has been found 

 equal to streptomycin in the treatment of tuberculosis. See Fig. 14-1, 



Courtesy of Abbott I^aboratoiies. 

 (a) 



Courtesy of The .Squibb Institute for 

 iNIedical IJesearfli. 

 (b) 



Fig. 14-1. Tubercle bacillus and streptomycin, (a) Photomicrograph of 

 infected limg tissue of mouse. The rod-like particles are Mycobacterium 

 tuberculosis, the microorganism that causes tuberculosis. Other dark areas 

 show accompanying cellular lung tissue, (b) Crystals of streptomycin tri- 

 chloride, the most useful antibiotic in the treatment of tuberculosis. 



Streptomycin, as can be seen from the structural formula, is a complex 

 organic base consisting of three parts: streptidine, streptose, and a methyl 

 derivative of glucosamine. The streptidine base contains two guanidino 

 groups (compare arginine, p. 120) which give streptomycin its salt-forming 

 characteristics. Commercial preparations of streptomycin are usually 

 the trihydrochloride or trihydrosulfate. Streptidine is clearly a deriva- 



