THE VOGES-PROSKAUER REACTION 155 



The significance of this reaction has not been fully appre- 

 ciated by bacteriologists, nor has it been generally realized that 

 the test is due to a definite end product of glucose fermentation. 

 It will therefore not be amiss to review somewhat in detail 

 the nature and chemistry of the Voges-Proskauer reaction. 



The reaction takes its name from the fact that it was first 

 observed by Voges and Proskauer in 1898, in their studies on 

 the "Bacteria of Haemorrhagic Septicaemia." They describe 

 the test as follows: 



On addition of caustic potash, we observed a new and interesting 

 color reaction. If the tube be allowed to stand 24 hours and longer 

 at room temperature, after the addition of the potash, a beautiful 

 fluorescent color somewhat similar to that of a dilute alcoholic solu- 

 tion of eosin forms in the culture fluid particularly at the open end 

 of the tube exposed to the air. We have investigated a few of the 

 properties of this coloring substance, which is not produced by the 

 action of the alkali on the sugar, and have found that it is fairly resist- 

 ant to the action of the external air. After a time however, it becomes 

 paler, and finally gives place to a dirty greenish brown. 



It has been repeatedly observed in this laboratory, that, 

 with some cultures, a distinct coloration which may be observed 

 about five hours after addition of the potash fades or disappears 

 entirely after twenty-four to forty-eight hours. 



In a study of the end products of the fermentation of glu- 

 cose by B. coll, Harden and Walpole (1905-06) observed that 

 the products ordinarily enumerated, (lactic, acetic, succinic 

 and formic acids, ethyl alcohol and carbon dioxide) do not ac- 

 count for all of the carbon in the sugar. Aside from these sub- 

 stances, a crude glycol was also obtained. This crude glycol 

 consists for the most part of 2:3 butyleneglycol (CH3-CHOH- 

 CHOH-CH3). On oxidation it yields acetyl-methyl-carbinol 

 (CH3, CHOH.CO.CH3), a volatile reducing substance, which, 

 when mixed with potassium hydroxide in the presence of pep- 

 tone, imparts an eosine-like coloration to the mixture on stand- 

 ing. Butyleneglycol is oxidized to acetyl-methyl-carbinol by 

 B. aerogenes, but not by B. coli. Harden (1905) ascribes the 

 Voges-Proskauer reaction to the production of this carbinol. 



