232 UTILIZATION OF CARBOHYDRATES 



of carbohydrates. Thus, when benzaldehyde is added to a suspension of yeast in 

 glucose solution a condensation product of benzaldehyde with acetaldehyde is formed 

 which seems to have the formula 



C6H5 • CHOH • CO • CH3 . 



This reaction, according to Neuberg, is brought about by the activity of an enzyme, 

 carboligase. Up to the present time similar studies have not been made with bacteria, 

 but it is not unreasonable to suspect that somewhat similar enzymatic processes may 

 be discovered. 



CARBOHYDRATES AND THE ENERGY REQUIREMENTS OF BACTERIA 

 THE SUGAR SERIES, AND DERIVED ALCOHOLS AND ACIDS 



Mention has been made above of the fact that the addition of utilizable carbo- 

 hydrates and carbohydrate derivatives of the proper configuration to the nitrogenous 

 constituents of cultural media may very materially affect the character of the prod- 

 ucts. 



Generally speaking, but with some well-known exceptions, as, for example. 

 Bacillus alcaligenes, which apparently does not utilize even glucose for energy, the 

 utilizable carbohydrate is burned for energy, sparing to a very considerable degree 

 thereby the nitrogenous constituents from bacterial attack.' No authentic instance 

 has been recorded in which a microbe utilizes any carbohydrate for energy that will 

 not utilize glucose. There are, however, organisms that do not seem to be able to 

 use any carbohydrate except glucose for energy. This is reminiscent of the human 

 body, which seems to utilize glucose for energy requirements. 



It is rather a striking fact, commented on long ago by Smith,^ that the bacteria 

 highly pathogenic for man and for animals are usually less reactive both culturally 

 and chemically than the parasitic types. Thus, typhoid, dysentery, diphtheria, and 

 tubercle bacilli, as well as meningococci and gonococci, are relatively inert culturally, 

 whereas the colon, proteus, and mesentericus groups of bacilli and the staphylococci 

 are characterized by considerable cultural reactivity. This is reflected not only in the 

 respective changes induced in nitrogenous constituents of culture media, but also in 

 the configuration of carbohydrates and carbohydrate-derivatives which these mi- 

 crobes can utilize for energy; which they can ferment. The members of the pathogenic 

 groups above mentioned can generally utilize glucose, and the closely related hexoses, 

 mannose, and fructose and the derived alcohol, mannitol, but cannot apparently 

 break down such biose molecules as lactose and saccharose, or utilize starches. 



On the other hand, there are parasitic microbes, as certain members of the 

 mucosus capsulatus group, which can ferment a very considerable variety of carbo- 

 hydrates, some with 3, 4, 5, 6, 12, and more carbon atoms. The exact explanation for 

 this difference in versatility, aside from Fischer's simile of the "key and the lock,"^ 

 is still to be revealed. Nevertheless, the remarkable specificity of these relations be- 

 tween carbohydrate configuration and protoplasmic utilization is one of the remark- 

 able phenomena of biology. 



' See Kendall, A. I.: Physiol. Rev., 3, 438. 1923. 



' Smith, T.: Am. Med., 8, 711. 1904. ^Fischer, E.: he. cil. 



