56 PHYSIOLOGY OF BACTERIA 



A dehydrogenation follows, and the acceptor for this 

 hydrogen is oxygen activated by the mold. The remain- 

 ing gluconic acid can be hydrogenated further in various 

 ways, and citric acid as well as oxalic acid are well- 

 known intermediary products. The final result is 

 CO2 and H2O. 



Fermentations of Proteins. — The protein molecules 

 are so large and so entirely unknown that it is entirely 

 out of the question to present equations for the fermenta- 

 tion of proteins. 



These large protein molecules can be attacked only 

 by a limited number of bacteria. The common division 

 of bacteria into those that liquify gelatin, and those 

 incapable of doing this, is no reliable indication for their 

 ability to attack protein molecules in general. While 

 the specificity does not seem to be as strict as with 

 carbohydrates, there is a certain amount of specialization 

 the chemical foundation of which is not as yet known. 

 (Rettger, Berman and Sturges, 1916, Berman and 

 Rettger, 1918.) 



The large protein molecule is broken up by those 

 microorganisms which have the power to do so, into 

 smaller molecules of similar nature which are still too 

 large to be described by a chemical formula. These 

 compounds, called albumoses, hemi-albumoses, pep- 

 tones, peptids and various other names, are usually 

 defined by the precipitants which will make them insol- 

 uble. A number of different compounds are used for 

 this purpose, such as dilute acids, copper salts, lead 

 salts, zinc salts, concentrated ammonium sulfate, tannic 

 acid, phosphotungstic acid, etc. 



The proportion of the total nitrogen contained in 

 these fractions gives a general conception of the course of 

 protein decomposition, and is of valuable information. 



