82 



SPIRAL TWL'^T A\D OPT. ACTIVITY 



lus mycoides, when grown on the surface of agar pep- 

 tone medium, produces colonies spirally twisting to the 

 left, i. e., counter-clockwise (according to the terminology 

 adopted by Ludwig, 1932). After one has introduced a 

 small quantity of inoculating material in the centre of a 

 Petri dish of agar-peptone, one soon sees it grow ; the thin 

 filaments of the growing culture begin to deviate to the 

 left (cf. Fig. 5). 



L 



D 



Fig. 5. Dextral (D) and sinistral (L) spiral twisting of the growing 

 filaments of colonies of Bacillus mycoides, as observed on peptone 

 agar, in Petri dishes. 



The inverse form of this organism, growing in dextral 

 coils, rarely occurs. It was first recorded by Gersbach 

 (1922), who described this interesting case as an ''isom- 

 erism in bacteria". He further established that the 

 dextral and sinistral strains are entirely identical in all 

 their properties. 



Later a single dextral strain among a great number of 

 sinistral ones was observed by Oesterle (1929). 



Lewis (1932) isolated several dextral strains in Texas. 



In an extended series of investigations with Bacillus 

 mycoides at the Microbiological Institute of the Academy 



