64 OPT. A CTn ., HEREDITY A^D EX 1 IROXMEXT 



conclusion that Pere's results are by no means confirmed 

 by Kayser's. 



This same table shows that racemization is greatly in- 

 fluenced by the culture medium. A given strain of bac- 

 teria, when cultured on a definite sugar, forms an almost 

 optically pure lactic acid (Pederson and collaborators, 

 1926, had shown that it is never entirely optically pure), 

 while on another sugar, it forms a racemic mixture. This 

 is the case, for instance, in the strains g, m, n, o, p. Ped- 

 erson and his collaborators (1926) made further observa- 

 tions on this point. 



There are also the recent researches of Tatum and his 

 coworkers (1932) in which 4 strains of lactic acid bacte- 

 ria producing laevorotatory acid, 3 strains producing the 

 dextrorotatory acid and 13 different strains of Clostri- 

 dium acetohutylicwn were used. These authors found 

 that lactic acid bacteria produce the optically pure form 

 of lactic acid when grown separateh/ and the racemic 

 form when grown in association with the microbe caus- 

 ing acetonebutylic fermentation {Clostridium acetohuty- 

 licum ) . 



At first Tatum (1932) interpreted his results in the 

 light of the hypothesis of Orla- Jensen (1919) according 

 to which there are in the bacterial cell two independent 

 enzymes, one of which produced the right and the other 

 the left lactic acid. In consequence of the association 

 of lactic acid bacteria with the butylic bacteria the meta- 

 bolism of the former would change in such a manner that 

 both optical isomers of lactic acid would start to be pro- 

 duced. However, in his later work (1936), Tatum showed 

 that, in the association of the two types of bacteria, lactic 

 acid is always initially formed m the optically active 

 state by the lactic acid bacteria, and that Clostridium is 

 only responsible for the subsequent racemization. (It is 

 interesting to note that racemization takes place in the 

 presence of antiseptics, therefore it is of enzymatic na- 

 ture.) The investigations were continued by Katagiri 



