CARBON METABOLISAL- 259 



Evidence that this is so is provided by the fact that 

 fiimaric and malic acids have been detected in the meta- 

 bolism solutions, and that oxalacetic, malic and fumaric 

 acids added to the system become converted to succinic 

 acid. 



An enzyme preparation has been obtained from M. 

 lysodeikticus which, in presence of magnesium or man- 

 ganese, and possibly phosphate, catalyses the carboxyla- 

 tion of p3^ruvic acid to oxalacetic acid. The enzyme only 

 decarboxylates pyruvic acid if co -carboxylase is also 

 present. When pyruvic, lactic or oxalosuccinic acids are 

 decarboxylated by the enzyme in presence of " labelled " 

 carbon dioxide there is no evidence of exchange of 

 carbon dioxide. Similarly after glucose or pyruvate 

 have been treated with Sir. lactis (which can convert 

 pyruvic acid into lactic and acetic acids and carbon 

 dioxide) in presence of " labelled " carbon dioxide, the 

 isolated pyruvic, lactic and acetic acids do not contain 

 " labelled " carbon. 



The mechanism of formation of propionic acid from 

 glycerol is not yet clear but it may arise via lactic acid : — 



CH2OH CH3 CH2 C'Hg 



I I -H2O II + 2H I 

 CHOH > CHOH > CH > CH. 



I I I I 



CH2OH COOH COOH COOH 



or via pyruvic acid : — 



CH2OH COOH COOH 



I I + 4H I 



CHOH > CO > CH2 -f H2O 



I I I 



CH2OH CH3 CH3 



When carbon dioxide is assimilated by other bacteria 

 it has been found to be distributed as follows : — Esch. 

 roll : in formic, acetic, lactic and succinic acids ; Aero- 

 hacter indologenes : in acetic, lactic and succinic acids ; 

 Proteus vulgaris, Str. paracitrovortis and Staph, aindidus : 



