228 UTILIZATION OF CARBOHYDRATES 



As early as 1862 Pasteur' was studying spontaneously developing butyric fermen- 

 tation; indeed, he had already isolated and cultivated the anaerobic "vibrios," as 

 he called them, which would induce the formation of butyric acid from lactates. This 

 is a highly significant phenomenon which has not received the attention it deserves 

 even today, inasmuch as it seems to predicate an extraordinary change of the three- 

 carbon-atom lactate molecule to the four-carbon-atom butyrate molecule. Pasteur 

 also made the highly important discovery that certain microbes attacked the d- and 

 /-forms of tartaric acid at materially different rates, thus paving the way for the 

 important studies of Fischer and Thierfelder^ upon the isomers of glucose and their 

 relations to yeast fermentation. Fischer, whose master-mind opened the great field 

 of carbohydrate chemistry to his successors, did not fail to realize the theoretical 

 importance of these relations between carbohydrate structure and protoplasmic 

 utilizability, and propounded his famous simile of the "key and the lock"^ in explana- 

 tion of the reciprocal relations between the two. 



Much additional information about the fermentations of carbohydrates by 

 bacteria was afforded by the earlier researches of Nothnagel^ and of Brieger^ who 

 isolated and identified propionic, lactic, acetic, and formic acids among the products 

 of decomposition of glucose by acetic and lactic fermenting microbes. Perhaps the 

 greatest contribution of all, however, was that of Escherich.^ This very careful 

 and thorough investigator not only introduced several of the more important intes- 

 tinal bacteria into the group of known microbes, but also added much to the tech- 

 nique of bacteriology, including the underlying principle of the fermentation tube. 

 He also improved the anaerobic method of cultivation, and, perhaps most significant 

 of all, started an entirely new chapter in microbic chemistry dealing with the nature 

 of the metabolism of proteins, carbohydrates, and fats by a variety of bacteria, acting 

 alone and in mixture, which he obtained from the intestinal tracts of young children. 

 With the advent of Escherich's important monograph, modern bacteriology may be 

 said to have its origin. 



GENERAL CONSIDERATIONS 



With the probable exception of the genera Thiothrix and Beggiatoa, bacteria 

 which appear to utilize inorganic sulphur and sulphur compounds and simple am- 

 monium salts for energy, 7 require some preformed, that is to say, organic food in 

 their dietary. This food is required in fulfilment of two distinct phases in their life- 

 history: the structural or anabolic phase and the energy or katabolic phase. The 

 structural phase comprises those phenomena which are embraced in the separation 

 and maturation of the daughter-cell from the parent-cell, together with those cellular 

 losses incidental to the elaboration of soluble enzymes and other elements. The 



' Pasteur, L. : The Physiological Theory of Fermenlation. An excellent translation appears in 

 "Harvard Classics," 38, 289-381. 1910. 



^ Fisher, E., and Thierfelder, H.: Ber. d. dent. chem. Gesellsch., 27, 2031. 1894. 



3 Fischer, E.: Ztschr.f. phys. Chemie, 26, 60. 1898. 



" Nothnagel, H.: Ztschr f. klin. Med., 3, 275. 1881. 



5 Brieger, L.: Ztschr.f. phys. Chemie, 8, 306. 1883-84; 9, i. 1885. 



^ Escherich, T.: Die Darmbakterien. Stuttgart. 1886. 



'See Waksman, S. A.: /. Bad., 7, 231. 1922. 



