- 34 



4) The orange red color of B. ruber iudicus I and II on 

 acid agar is probably due to alkali-production. Query: - - Is the 

 large amount of acid formed byB. ruber indicus in bouillon and 

 on ordinary meat agar, as evinced by its better growth on alkaline 

 meat agar. a result of the meat albumins? 



5) The range of color in B. amyloruber, as follows: 



Red Orange Blue 



1,5 / acid 87 10 3 



Saccharose 70 20 10 



Dextrose 50 30 20 



Neutral and Lactose 65 15 20 



1,5 % alkaline 45 55 



6) the inhibition of pigment by dextrose in the case of B. ru- 

 tilus, although the saccharose tube shows evidence of assimilation, 

 i. e., is like 1,5 / acid. 



After five days' growth some of these cultures were slightly less 

 characteristic, as would naturally result from the constantly increasing 

 complexity of the metabolic products. For example, B. pro- 

 digiosus IV had become vermilion on 1,5 % acid agar, no doubt 

 as a result of the alkali produced by the vigorously growing culture. 

 Other of the more slowly developing cultures bore out the results 

 of the first 48 hours, e. g., B. prodigiosus I IV had produced 

 orange red pigment on 1,5 alkaline agar, and B. plymouthen- 

 sis I slight violet red color on acid agar. Metallic green luster 

 had appeared for several cultures, noticeably for B. ruber balti- 

 cus on 1,5 % acid agar, and for B. plymouthensis I and II 

 on dextrose and on saccharose agar. Orange red color had 

 changed to red on lactose agar for B. prodigiosus V and for 

 B. rutilus, but excepting these and the colorless lactose agar cul- 

 tures of B. ruber miquel and B. plym. II, the orange tone still 

 held for the series on this medium, i. e., the alkali produced by the 

 bacteria was not neutralized by acid formed from the sugar. It 

 would seem that since B. ruber balticus, B. plymouthensis I, 

 and B. miniaceus ferment lactose with gas production, these cul- 

 tures would show a decrease of the orange tone. 



Although the relative results arrived at on the above media are 

 of some value, their absolute value is lessened because of the 

 unknown factors present in agar and peptone. Agar itself contains 

 a certain amount of carbohydrate, galactose (Bauer, Jour. Prakt. 

 Chemie, B. XXX. p. 367), which is probably assimilable by the organisms. 

 A further reduction of the medium, by leaving out the peptone, 

 resulted in very feeble white growth in five days. Three cultures 

 only showed a trace of pigment, B. ruber indicus II, 

 B. rutilus, and B. prodigiosus VII. The last named showed 

 a green iridescence on the thin pink layer. 



In the endeavor to do away with agar and still have a solid 

 medium for pigment production, the following mixtures were employed, 

 and gave interesting comparative results. The flour and starch were 

 cooked, poured into Petri dishes, sterilized by discontinuous method, 

 and inoculated. 



