NITROGEN METABOLISM OF BACTERIA 391 



galactose and fructose were without effect. He believed that the 

 acid formed played no role, since the addition of calcium car- 

 bonate to the medium did not influence the results. Fischer 

 concluded that the inhibitive action of the glucose is due to an 

 inactivation of the proteolytic enzyme of the organism. This 

 view is partly in harmony with the theory recently advanced 

 by Homer (1916), according to which a chemical union is formed 

 between the aldehyde group of the glucose and a portion of the 

 tryptophan molecule. The combination is more resistant to 

 attack than free tryptophan. 



EXPERIMENTAL 



A study of the behavior of certain organisms in glucose pep- 

 tone broth was first undertaken. The test medium contained 

 peptone (Witte) 0.25 per cent, sodium chloride 0.5 per cent, and 

 glucose 1.0 per cent. The same medium minus the sugar was 

 used for control purposes. The test and control solutions were 

 transferred in 10 cc. quantities to test tubes, and inoculated with 

 the test organisms. At the end of four weeks of incubation at 

 37°C. the watei of evaporation was replaced and biuret tests 

 made according to the method of Vernon (1904). The Sorensen 

 (1908) method for the determination of amino acids was also 

 carried out, as well as the Benedict test for the presence of 

 unchanged sugar. The results are presented in table 1. 



Barring one exception, no protein decomposition occurred in 

 the presence of glucose. Bacillus subtilis alone was able to 

 digest the peptone in the glucose-containing medium. In every 

 other instance the biuret and Sorensen tests gave the same 

 figures as in the uninoculated controls. The acidity in the 

 glucose tubes was increased, with the exception of the case of 

 Bacillus ramosus. Owing to the unfavorable temperature for 

 this organism, Bacillus ramosus grew but sparingly. The diges- 

 tion of the peptone by Bacillus subtilis, even though the glucose 

 was not completely fermented, is an indication that a glucose- 

 utilizing organism may secrete a proteolytic enzyme in the 

 presence of a fermentable sugar. 



