SUBSTANCES PRODUCED BY ANIMALS 215 



The ability of Torulosfora utilis var. major to inhibit the growth of 

 various gram-negative and other bacteria has also been demonstrated 



(112). 



SUBSTANCES PRODUCED BY ANIMALS 



To what extent antibacterial substances produced by animals and 

 plants should be classified with the true antibiotics is open to question. 

 In view of the fact, however, that these substances behave in a manner 

 similar to antibiotics, they can be mentioned here. 



Lysozyme 



Fleming (260) found that egg white contains an enzyme, designated 

 as lysozyme, that is active against certain bacteria, notably micrococci, 

 bringing about their lysis. It is soluble in water and in dilute NaCl solu- 

 tion. It is precipitated by chloroform, acetone, ether, alcohol, and tol- 

 uene. It is not acted upon by pepsin or trypsin. 



Lysozyme has been demonstrated in most mammalian tissues and 

 secretions, in certain vegetables, and in bacteria (905). It was found to 

 be a polypeptide containing 16 per cent nitrogen and 2 to 3 per cent 

 sulfur and having a molecular weight of 18,000 to 25,000. It is soluble 

 and stable in acid solution, insoluble and inactivated in alkaline solu- 

 tions, and inactivated by oxidizing agents (641 ). It diffuses in agar and 

 through cellophane, and thus is markedly different from bacteriophage 

 (332). It is fixed on the bacterial cells. It acts primarily upon the 

 cell membrane of bacteria, the highly viscous component of the bac- 

 terial cell (the mucoids), especially the sugar linkages of the complex 

 amino-carbohydrates, being disintegrated by the enzyme. The degrada- 

 tion of the bacterial polysaccharide to water-soluble products (N-acety- 

 lated amino-hexose and a keto-hexose) by lysozyme is accompanied by 

 complete lysis of some of the bacteria. In the case of other lysozyme- 

 sensitive bacteria, such as B. suhtillsy no lysis occurs j apparently the 

 morphological structure of these bacteria does not depend exclusively 

 on the unaltered state of the substrate for lysozyme (242). 



The formation of a lysozyme-like material was also demonstrated 

 (259) for a coccus isolated from dust. A sarcina susceptible to egg-white 



