ANTIBACTERIAL ACTION 233 



cocci, and gram-positive, spore-forming bacteria are insensitive to 

 gramicidin J tyrocidine has more activity against gram-negative organ- 

 isms and is more bactericidal, whereas gramicidin is primarily bacterio- 

 static. 



Tyrocidine destroys immediately and irreversibly the metabolic ac- 

 tivity of the bacteria, such as oxygen uptake and acid production. For 

 most tissue cells, with the exception of spermatozoa, gramicidin is much 

 less toxic than tyrocidine. It behaves like a specific inhibitor of certain 

 metabolic reactions. It retains much of its activity in vivo. 



Tyrocidine brings about rapid cytolysis of the cells. There is a quan- 

 titative relation between the concentration of the antibiotic and the 

 number of cells lysed, namely i mg. for lo^ and o.i mg. for lo^ cells. 

 The amino acid decarboxylases are not inhibited even by concentrations 

 of tyrocidine of 0.3 mg./ml. (309). 



Other Antibiotics from S-p ore-forming Bacteria 



The other antibiotic substances isolated from spore-forming bacteria 

 are characterized by bacteriostatic spectra quite difFerent from that of 

 tyrothricin. This is brought out in Table 37. Some of these substances, 



TABLE 37. COMPARATIVE ANTIBIOTIC SPECTRA OF SUBSTANCES PRODUCED 

 BY AEROBIC SPORE-FORMING BACTERIA 



From Foster and Woodruif (284). 



Note. Unit of activity is the amount of antibiotic required to inhibit S. aureus as test bacterium. 



like subtilin, are capable of destroying various bacterial toxins, such as 

 diphtheria, tetanus, and others, as well as hemolysin (759). 



Subtilin was found to be similar to gramicidin in its effect upon sur- 

 face tension, in producing hemolysis, even if more delayed, in killing 



