SPIRAL TWIST Ay D OPT. ACTIYTTV 87 



media. There is definitely in the dextral form a special 

 sensitivity to heat injury at the temperatures indicated. 

 It is interesting to compare this characteristic weakness 

 of the inverted dextral form with the following property 

 pointed out by Le^\ds (1933) and observed again by Gause 

 (1939). 



b. Enzymatic properties. Lewis, working 

 with dextral and sinistral strains of Bacillus mycoides, 

 reported a specific physiological difference between them. 

 It is known that this bacillus possesses the ability to 

 decompose glucose and saccharose and to acidify the me- 

 dium. On glucose the acid production is similar in sinis- 

 tral and in dextral strains but not on saccharose. Accord- 

 ing to Lewis the formation of acid on saccharose is rapid 

 with the left spiralled strain and it ceases with the right- 

 spiralled type. 



Gause (1939) repeated these experiments using the S- 

 form of Bacillus mycoides. Tw^o per cent saccharose and 

 a little quantity of a weak (0.02 per cent) solution of 

 phenol red (according to Clark) were added to an agar- 

 peptone medium of usual composition. At pH 7.7, which 

 is the optimal hydrogen ion concentration for the gro^\i:h 

 of Bacillus mycoides, phenol red has an orange tint. The 

 culture w^as kept at 28° C. Nineteen hours after the be- 

 ginning of the experiment the color of the sinistral 

 strains differed very sharply from that of the dextral. 

 The former showed a rapid production of acid, the pH 

 of the colony being about 6.8. The dextral strains showed 

 no production of acid. The reaction of the colony was 

 alkaline, its pH being about 8.4. Lewis' results were 

 therefore confirmed with the S-form of the bacillus. 



It might be worth mentioning the following detail. 

 While the dextral strains are, without exception, unable 

 to produce acid on sucrose, the sinistral strains were all 

 able to form acid except in two cases, one mentioned by 

 Lewis and another (doubtful) observed by Gause. 



