Variability in Bacillus prodigiosus. 



Proceedings of the Section of Sciences, Kon. Akademie van Wetenschappen, Amster- 

 dam, Vol. XII, 1910, p. 640 649. -- Verscheen onder den titel VariabiIiteit bij Bacillus 

 prodigiosus* in Verslagen Kon. Akademie van Wetenschappen, Wis-en Natuurk. Afd., 



Deel XVIII, 1910, biz. 596605. 



In a former paper 1 ) I showed how easily new constant variants of Bacillus 

 prodigiosus and other microbes may be obtained. Here follow some further 

 observations, made with the aid of Mr. H. C. Jacobsen, assistant in my La- 

 boratory. 



T/t keeping constant of the cultures. 



The principle on which the keeping constant of B. prodigiosus seems to re- 

 pose is preventing the cultures from becoming alkaline by their own action. Thus, 

 by re-inoculating in quick succession, for instance every 24 hours, into bouillon 

 or on bouillon-agar at 30 C., each form of Bacillus prodigiosus, whether the na- 

 tural or normal form, .or a variant obtained from it, remains unchanged probably 

 for an indefinite time. 



For the transplantations only very little material must be used and abun- 

 dance of food. 



If some lactic acid is added, for instance 0,5 to 1.5 cm 3 normal per 100 cm 3 

 of bouillon, the culture likewise remains unchanged after a prolonged series of 

 transports, if these are always carried out before the acid is neutralised by the 

 alkali produced from the bouillon by the bacteria themselves 2 ). 



Addition of i to 2 pCt. of glucose acts in the same manner as free acid, 

 B. prodigiosus therefrom producing acid which may rise, if sufficient glucose is 

 added, to 3 to 4 cm 3 normal per 100 cm 3 of bouillon. As the titre of alkali, ori- 

 ginating in the bouillon alone, can amount to 2.5 cm 3 N per 100 cm 3 of bouillon, 

 and as from I pCt. of glucose there results no more than 1.5 to 2 cm 3 N of 

 acid, addition of I pCt. of glucose is sufficient to prevent variation, if the re- 

 inoculations take place quickly; but not if effected with long intervals, for in the 

 latter case more alkali may result from the bouillon than acid from the glucose. 



If to the bouillon so much ammoniumcarbonate or natriumcarbonate is added 

 that the titre of alkali amounts to about 3 cm 3 N per 100 cm 3 of the medium, 



') Royal Acad. of Sciences, 21 Nov. 1900. 



-) At 4 cm 3 of acid per 100 cm* of culture liquid the growth of B. prodigiosus is 



slackened, at 9 cm 8 it is quite stopped. 



