JW 



37 \ ' 



These series bring out interesting results in the behavior of the 

 cultures. In standard aspafagin solution (Sol. A), B. prodigiosus I, 

 tested five times, and B. prod. II VI and VIII, tested twice, grew 

 luxuriantly, i. e., showed dense white cloudiness, but showed no trace 

 of pigment. B. ruber balticus, B. plymouthensis I and 

 II and B. r u t i 1 u s gave the same results , except that B. 

 rutilus developed less cloudiness. On the other hand B. prod. 

 VII, B. ruber indicus I and II, B. ruber miquel, and 

 B. amyloruber produced a good red coloration of the medium, 

 but none grew luxuriantly, except B. ruber miquel and B. 

 prod. VII. 



In the next series (Sol. B), MgS0 4 was eliminated from the 

 medium in an attempt to determine whether this substance be neces- 

 sary for the elaboration of red bacterial pigment, as has been shown 

 for the fluorescent pigment. Nearly all the cultures developed, 

 although less readily than in Sol. A; three of them, B. ruber 

 indicus I and II, and B. prodigiosus VII, although showing 

 scarcely any cloudiness, colored the solution a beautiful red in 

 48 hours. With these three cultures which gave pigment in the 

 absence of MgSO 4 further tests were made. A pure 0,2 / solution 

 of asparagin was prepared, and flasks were inoculated by touching 

 the surface of an agar plate colony with a fine needle, or from a 

 growth in Sol. B. In each case B. ruber indicus I and II produced 

 no distinguishable cloudiness of the solution, but slowly and gradually 

 colored it as deep a red as they did the standard solution. B. pro- 

 digiosus VII failed to show pigment here, and control cultures of 

 B. ruber balticus and B. ruber miquel also remained perfectly 

 clear and colorless. 



These results point toward one of two conclusions. Either the 

 pigment of some cultures of what is here designated as the Prod i- 

 giosus group has a different chemical basis from that of others of 

 the group, or on the other hand, great variation occurs among these 

 cultures in their ability to elaborate the same pigment out of the 

 same synthetic material. The results of chemical and spectroscopic 

 analysis of the pigments of B. prodigiosus, B. ruber balticus, 

 and B. ruber indicus (19), (45), (49) give us no reason to believe that 

 they are essentially different. Further, the fact that some cultures 

 do not produce pigment in a 0,2% asparagin solution even in the 

 presence of MgS0 4 , while others beside B. ruber indicus have 

 this power, indicates a continuous, rather than a discontinuous variation 

 of the ability to elaborate pigment. Whatever the cause of this may 

 be, it appears from my results to the present time that the different 

 strains or varieties are very constant in their ability or non-ability 

 to form pigment in the above solutions, whether the latter be in- 

 oculated from young or old cultures on various media. 



In his work on B. prodigiosus, Kuntze used 12 % 

 asparagin and 0,1 0,2 / K 2 HP0 4 , obtaining pigment if MgS0 4 were 

 added in smallest crystals. In order to determine whether lack of 

 pigmentation in my series was due to an insuffiency of the organic 

 compound, I increased the asparagin content to 1 %. The first trial 



