SPIRAL TWTST AND OPT. ACllYTTY 95 



One may conjecture that the inversion of the direction 

 of the spiral growth in Bacillus mycoides is related to an 

 optical inversion of some secondary substance in meta- 

 bolism. The latter would bring about the inversion of 

 some structures in the cell wall and, from the interaction 

 of these with the forces inducing the spiral twist, there 

 would result an inversion in the direction of the spiral 

 grow^th of the cells. 



But to what extent can one assume that the secondary 

 substances of metabolism which participate in the struc- 

 ture of the wall of the bacterial cell can undergo an optical 

 inversion? Some recent data on the chemical structure 

 of bacterial capsules obtained by Bruckner and Ivanovics 

 (1937) in the laboratory of Professor Szent-Gyorgyi, are 

 of interest in this connection. As is kno^vn, the cell wall 

 in bacteria consists of two layers: (1) A very thin in- 

 ternal cuticle, and (2) An external gelatinous layer which 

 is sometimes developed into an envelope called a capsule. 

 (John-Brooks, 1930, remarks that the bacteriologists have 

 come to look upon capsule formation as a general feature 

 which is common to all bacteria, but which reaches the 

 proportions that we know, only in certain species.) Bruck- 

 ner and Ivanovics (1937) w^ho studied the chemical prop- 

 erties of the capsule of Bacillus antJiracis and of some 

 other species of bacteria, all of which are aerobic spore 

 formers, standing near Bacillus mycoides in the classifi- 

 cation, found that the capsule of these bacteria consists of 

 a polypeptide substance, the hydrolysis of which yields 

 d(-) glutamic acid. The laevorotatory isomer of this 

 amino acid is unnatural, and it has not been found pre- 

 viously anywhere in the organic nature. So, the presence 

 of the unnatural glutamic acid in the structure of the 

 envelope of the anthrax and of some other bacilli has 

 already been recorded in the literature. Further investi- 

 gations in that direction may reveal significant data on 

 the present problem. 



