Bacterial Metabolism 



69 



ing knowledge on bacterial fermentations, was able to start 

 with the thesis that "the primary mechanism found in 

 muscle and yeast, the operation of which results in the 

 formation of pyruvic acid, is found also in those bacteria 

 which ferment carbohydrates." This thesis is no longer 

 tenable, and no one should assume the existence of a 

 glycolytic mechanism in a bacterium without clear and 

 specific proof. 



Gluconic Acid Pathway. The first example of a non- 

 glycolytic pathway of glucose oxidation by bacteria was dis- 

 covered long before glycolysis was known. 



HCOH 

 HOCH 0^-2H 

 HCOH 

 HC- 



X 



CH^OH 

 GLUCOSE 



HCOH 



HOCH 



HCOH 



HC 



CHgOH 



H^D 



P 



C'-OH 

 HCOH 

 HOCH 

 HCOH 

 HCOH 

 CH2OH 



-2H 



GLUCONOLACTONE GLUCONATE 



■2H 



-2H 



C-OH 



c=o 



HOCH 

 HCOH 



HCOH 



.0 



C-OH 

 HCOH 



HOCH ^ 9 



HCOH 



CH2OH 

 5-KETOGLUCONATE 



/P 

 C-OH 



C = 



HOCH 



HCOH 



C=0 



CH^OH 

 2- KETO GLUCONATE 



6H2OH 



2, 5" Dl KETO' 

 GLUCONATE 



FIGURE 1. Gluconic Acid Pathways 



In 1886, Brown found that species of Acetobacter oxidize 

 massive amounts of glucose to gluconic acid. Not long after- 

 ward, Bertrand obtained evidence for the further oxidation 

 of gluconate to 5-ketogluconate by Acetobacter xylinum. 

 Recently Katznelson, Tannenbaum, and Tatum (13) 

 studied glucose and gluconate oxidation by another species, 

 Acetobacter melanogenum, which is characterized by for- 

 mation of a brown water-soluble pigment. The investigators 

 have provided convincing evidence that this organism 



