LEO F. RETTGER 223 



property is possessed by certain anaerobes only, among the most important of which 

 are CI. sporogenes, CI. putrificum, and CI. aerofetidum. 



Some bacterial species attack casein, without being able apparently to exert any act- 

 ion on serum or egg albumin. Certain staphylococcus and streptococcus forms belong 

 in this class. Gelatin is frequently liquefied by organisms which are non-pro-teolytic. 

 In some instances the gelatin appears to be reduced to the soluble gelatose stage only. 



The decomposition of organic waste is participated in by many kinds of bacteria. 

 According to Tissier and Martelly,' and this is a common observation, aerobes and 

 facultative anaerobes play an important part by preparing a favorable gaseous environ- 

 ment for the proteolytic anaerobes through which rapid destruction takes place. 



INFLUENCE OF CARBOHYDRATE ON METABOLISM 



It has long been known that utilizable carbohydrates retard bacterial proteolysis. 

 This principle has in recent years been re-emphasized by KendalP and his associates, 

 who apparently coined the statement, "Fermentation takes precedence over putre- 

 faction." Their numerous experiments with glucose-utilizing organisms, particularly 

 of the coli-typhi-paratyphi group, have lent further support to the limited obser- 

 vations of earlier investigators. 



Kendall and his co-workers showed that when glucose-attacking organisms are 

 grown in nutrient peptone containing i per cent glucose, very little nitrogen metabo- 

 lism is carried on as indicated by ammonia determinations, in comparison with control 

 cultures which contained no glucose. This inhibition of proteolysis was explained 

 by them to be a sparing action on the proteoses and polypeptides of the medium by 

 the glucose. 



Ordinary market milk is prevented from undergoing putrefaction because of the 

 lactose and the lactose-utilizing bacteria {Streptococcus lactis in particular) which are 

 always present. The lactic acid which is formed, even in small amount, retards the 

 development of proteolyzing organisms, as, for example, members of the B. subtilis 

 group and the putrefactive anaerobes, and instead of showing evidence of putrefaction, 

 the milk becomes more and more acid, and the casein is precipitated as an acid curd. 



Many other examples may be cited, as, for instance, the absence of proteolysis in 

 frozen stored eggs which may contain large amounts (10 per cent) of cane sugar. 



It seems to be well established that this inhibition of proteolysis is due to increased 

 H-ion concentration resulting from the sugar fermentation. Berman and Rettger^ 

 showed that this inhibition may be prevented by the addition of sufficient bufifering 

 agent to regulate the H-ion concentration. 



The retardation of proteolysis varies, however, with the different organisms, ni- 

 trogenous substances, and carbohydrates employed. For instance, indol production 

 by indol-producing strains of Bad. coli in ordinary peptone broth is prevented by the 

 addition of from 0.5 to i.o per cent glucose. In the presence of added tryptophane, 

 some indol may be formed. When lactose is substituted for the glucose, indol forma- 

 tion may be demonstrated readily. Both of these sugars are fermented by Bad. 



' Tissier, H., and MarteUy: Ann. de I'lnst. Pasteur, 16, 865. 1902. 



^ Kendall, A. I., and Farmer, C. J.: J. Biol. Chent., 12, 13, 19, 215, 219, 465, 469; i3, 63. 1912. 



3 Berman, N., and Rettger, L. F.: J. Bad., 3, 389. 1918. 



