VOL. 12 (1953) 



PATHWAYS OF ACETATE OXIDATION 



241 



TABLE I 



OXIDATION OF INTERMEDIATES OF THE CITRIC ACID CYCLE BY MeruHuS ntVeUS 



Phosphate buffer, 0.03M, pH 5.54. Substrates, o.oiM. Temp. 26''. Time 120 minutes. 



the ratio of the undissociated acid. Barron et al.^ thus found that Corynchacterium 

 creatinovorans , which did not oxidize succinate at pH 7, did oxidize it rapidly at pH 5.5. 

 Citrate was not oxidized at any pH. Therefore, pH 5.5 was used in these experiments. 

 Aerobacter aerogenes, grown repeatedly in an acetate medium, oxidized ketoglutarate 

 succinate, and acetate at a rapid rate; and citrate at a very slow rate (Fig. i). Merulius 

 niveus oxidized acetate at a rapid rate ; pyruvate and glycolate slightly ; succinate, cit- 

 rate, and malonate not at all (Table I). Pseudomonas fluorescens , which — like C. 

 creatinovorans - does not ferment glucose, 

 oxidized acetate to 70 % of complete oxid- 

 ation (Fig. 2). It oxidized pyruvate readily 

 although in the absence of oxygen no dis- 

 mutation occurred (Fig. 3) ; acetate and suc- 

 cinate at about the same speed; ketoglut- ■^^1" 



60 



120 



180 



2W 



Fig. 2. Oxidation of Acetate by Pseudomonas 

 ■fluorescens. Buffer, o.o3Af phosphate, pH 6.9. 

 Acetate, 10 micromoles. Abscissa, time in minu- 

 tes. Ordinate, O2 uptake in ^1 (blank subtracted). 



Fig. 3. Oxidation of Pyruvate by 

 Pseudomonas fluorescens. Phosphate 

 buffer, 0.0371/ pH 6.9 for Og uptake; 

 bicarbonate - NjiCOj pH 7.2 for dis- 

 mutation and COg formation. K pyru- 

 vate, o.oiM (30 micromoles.) Abscissa, 

 time in minutes. Ordinate, Og uptake 

 or CO2 production im /tl (blank sub- 

 tracted). I. O2 uptake; 2. COg produc- 

 tion. 



arate less rapidly; and citrate very slowly (Table II). It is known that ketoglutarate 

 accumulates during the oxidation of glucose by these bacteria^^. Tetrahymena geleii 

 References p. 24.^. 



