On Voges and Proskauer s Reaction for Certain Bacteria. 425 



Voges and Proskauer, commencing at the open end of the tube exposed to 

 the air. This suggests oxidation as a factor in the phenomenon, and as 

 acetylmethylcarbinol is very readily converted by oxidation into diacetyl, 

 (JH3.CO.CO.CH3, this substance was tested. Diacetyl yields the fluorescent 

 red coloration with peptone water and caustic potash in a few minutes, and 

 by its aid a much greater depth of colour can be obtained than that observed 

 with bacterial cultures. 



Voges and Proskauer's reaction, therefore, appears to be due to 

 acetylmethylcarbinol, which is formed by the action of the bacteria on the 

 glucose of the medium. In the presence of potash and air this is oxidised 

 to diacetyl, which then reacts with some constituent of the peptone water. 

 That diacetyl is the active substance and not p-xyloquinone, C6H 2 2 (CH3)2, 

 which is readily formed from it by the action of alkalis, is shown by the fact 

 that if the diacetyl be allowed to stand for some time with potash solution, 

 and peptone water be then added, no reaction occurs. 



B. cloaca; (Jordan), which gives Voges and Proskauer's reaction, was also 

 found to yield acetylmethylcarbinol, which was recognised by its power of 

 reducing Fehling's solution in the cold and of yielding the characteristic 

 phenylosazone of diacetyl with phenylhydrazine. 



Acetylmethylcarbinol has also been observed as a product of the action of 

 certain other bacteria on glucose. Thus, Grimbert* found that it is produced 

 by B. tartricus, and Desmotsf that it is also formed by the various bacilli 

 of the mesentericus group and by B. svMilis and Tyrothrix tenuis. These 

 bacteria should, therefore, give Voges and Proskauer's reaction, and, as a 

 matter of fact, B. mesentericus fuscus, the only one which has so far been 

 examined, gives the reaction quite characteristically when grown in peptone 

 water containing 2 per cent, of glucose. 



A number of other bacteria are being examined and attempts are also 

 being made to ascertain what constituent of the peptone water it is that 

 reacts with the diacetyl. 



* 'Compt. Bend.,' 1901, vol. 132, p. 706. 

 t ' Compt, Rend.,' 1904, vol. 138, p. 581. 



