PROCEEDINGS OF 



THE ROYAL SOCIETY. 



Suction B. — Biological Sciences. 



The Chemical Action of Bacillus cloacae (Jordan) on Citric and 

 Malic Acids in the Presence and Absence of Oxygen. 

 By James Thompson. 



(Communicated by Arthur Harden, F.R.S. Eeceived August 27, — Eead 

 November 14, 1912.) 



(From the Biochemical Department, Lister Institute.) 



The chemical action of Bacillus cloacce on citric acid and on malic acid has 

 not up to the present been investigated. 



Since this organism is a facultative anaerobe, the experiments were under- 

 taken with the object of ascertaining the effect of the presence of oxygen on 

 the course of the fermentation produced. It was found, however, that the 

 organism could not grow on ammonium malate in the absence of oxygen, so 

 that the observations on this subject were limited to the case of citric acid. 



Emmerling(l) has described the decomposition of malic acid by 

 B. lactis aerogenes (Escherich), a very closely allied organism, and Bosworth 

 and Prucha (2) have shown that, during the souring of milk, the citric acid 

 present in fresh milk is converted by B. lactis aerogenes into acetic acid and 

 carbon dioxide. 



I. In investigating the chemical changes produced by the action of 

 B. cloacce on various media, the determination of the respiratory coefficient 

 was first undertaken. For this purpose the apparatus described below, and 

 shown diagrammatically in the annexed figure, was used. 



Two burette tubes (a) and (5), fitted with two-way taps (Ji) and {%), are 

 connected by a capillary tube (c). To each are attached by stout rubber 

 tubing the pear-shaped receivers (d) and (e). The incubation tube (/), 



VOL. LXXXVI. B. B 



