CARBON METABOLISM 



251 



b}' lieterotropliic ]:)a.cteria it has been shown that succinic 

 acid is formed by tiie condensation of ])yruvic acid with 

 carbon dioxide followed by reduction via malic and 

 fumaric acids (see p. 258). It is probable, therefore, 

 that succinic acid does not arise by the splitting of a 

 six-carbon molecule into four-carbon and two -carbon 

 fragments. Succinic acid may also be formed by the 

 reductive deamination (p. 228) of aspartic acid : — 



> COOH.CH,.CH,.COOH + NH, 



NHs 



2. True alcoholic fermentation (to a small extent). 



3. Lactic, acetic and formic acid production, with 

 or without gas production. The last two types of fer- 

 mentation need phosphorylation v as a preliminary step. 

 The three fermentations suggested by Kluyver are sum- 

 marised by the following scheme : — 



CH80H.CH.(OHOH),.CHOK (glucose) 



' — o — ' 



I NajHPO* (as in alcoholic 

 I fermentation) 



2CHs.C0.C^0H >■ CH.CHOH.COOH 



OH 



(metliylglyoxal (lactic acid) 



liydrat*) 



4- 4 



CHjGH.CHsOH-f-CHO.CHOH.CHOH.CHO 

 (ethylene glyopl) (tartaric dialdehyde) 



CHj.CHO + 11,0 



C00H.CH2.CH,.('00H 



(sjiccMiic aciil) 



CHsCOOH + CHaCHjOH 

 (acetic (alcohol) 



acid) 



Non-phosphoiy!atod. 



4 

 CH3CH0 



4 



H.COOII 



I 



CH,COOH CH.CH.OH 



Pho8phorylat«d. 



Hj + COj 



The same types of fermentation occur with Eherth. 

 typhosa, except that the breakdown of formic acid 

 does not occur. It will be noticed that in this type of 

 fermentation the ratio of carbon dioxide to hydrogen is 

 1:1, and it will be remembered that members of the 

 coli-typhoid group of bacteria have a negative Voges 



