24 BULLETIN 782, U. S. DEPARTMENT OF AGRICULTURE. 



The table shows that only a few cultures were able to ferment 

 mucic, tartaric, and glyceric acid, in which there is a secondary 

 alcohol radical connecting a carboxyl with another alcohol radical, 

 as in mucic COOH(CHOH),COOH, tartaric C00H(CH0H)2C00H, 

 and glyceric CH20H(CH0H)C00H. It seems to be somewhat easier 

 for this group of bacteria to obtain carbon from glyceric acid when a 

 primary alcohol radical (CHjOH) replaced a secondary (CHOH). 

 Only 7 cultures were able to ferment tartaric acid, while none of the 

 68 cultures were able to utilize gly colic acid. Tartaric acid has a 



CHOH COOH 

 structural formula | where an alcohol radical is linked 



CHOH COOH 



CH^OH 

 to a carboxyl and another alcohol, while in glycolic | an alcohol 



COOH 

 radical is merely linked to a carboxyl. This difference in manner in 

 which the alcohol radical is linked to the carboxyl may make it 

 possible for some bacteria to ferment tartaric acid. In malonic 



/COOH 

 acid CHj two carboxyls are linked by a methyl group and it was 



\COOH 

 found that 11 of the 68 cultures were able to obtain carbon from 

 this source, while none of them were able to ferment oxalic acid 

 COOH 



I when 2 carboxyl groups are joined directly. In this case 



COOH 



it seems that the presence of the methyl group connecting the carboxyl 

 group makes it possible for a few cultures to obtain carbon, probably 

 from the methyl radical. Our results indicate that carbon is not 

 obtained from the carboxyl group, since none of the cultures were 

 able to utilize oxalic acid. This, however, may be due to the poison- 

 ous character of the acid. Whether this nonfermentability of the 

 exalate is due to the configuration of the molecule or to the poisonous 

 character of the compound, it is interesting to note that the work of 

 Doryland (5) confirms this result as he was unable to obtain fer- 

 mentation of oxalate when used as the only source of carbon in a 

 synthetic medium in which 225 different bacteria were studied. 



A large number of the cultures could utilize carbon from the 

 sodium salt of formic acid. It is possible to consider the structure 



^O 

 of this acid HO-C and it seems evident that the carbon can be 



\H 

 obtained from the aldehyd radical. If the structure is taken as 

 H-COOH the organism would have to obtain carbon from a carboxyl 

 group, and if they are able to do this with formic acid they should be 

 expected to ferment oxalic acid. 



