622 



SCIENCE 



[N. S. Vol. XLI. No. 1060 



of color at 20° C. at the beginning of the experi- 

 ment. The organism was subjected to phenol only, 

 beginning with a few minutes' exposure to a 0.75 

 per cent, solution and increasing as it became 

 more resistant up to fifty or sixty minutes. Cul- 

 tures were made on agar and grown at 20° C. 



A striking increase in color production on all 

 media resulted, the color becoming deeper and 

 deeper until the maximum was reached at the 

 thirteenth exposure. Up to the nineteenth ex- 

 posure the color of each succeeding growth be- 

 came most pronounced in 48 hours. Prom 

 thereon, with increasing time exposures, the color 

 production was slower, the color reaching its max- 

 imum in three or four days. Different shades of 

 red were produced on diiferent media. On agar, 

 the color was deep brick red; on blood serum it 

 had more of a scarlet hue; while on potato the 

 color was somewhat variable and not as marked as 

 on the other media. It was, however, on glycerin 

 agar and glycerin potato that the most striking 

 results were observed. The original strain gave 

 no color on glycerin agar, and only a pale, delicate 

 reddish color on glycerin potato. Transplants 

 made from the phenol exposed organisms gave a 

 brilliant cherry-red color on glycerin potato 

 spreading to surround the entire surface of the 

 medium. On glycerin agar, a dull cherry-red color 

 was obtained. 



In summing up what has been said concerning 

 chromogenesis, it becomes' evident that this faculty 

 is more or less elosely associated with the meta- 

 bolic a,ctivities of bacteria, nutritive or otherwise. 

 It varies with the strain and is more or less de- 

 pendent on oxygen, temperature, and the medium 

 used. An organism may produce more than one 

 color at once and the same time or it may produce 

 different colors, depending upon environment and 

 the medium used, particularly the latter. Finally, 

 chromogenesis may be varied through the agency 

 of chemicals, as seen by the work here outlined, 

 phenol generally increasing, and glucose, sodium 

 chloride and sodium sulphate diminishing this 

 function. 



Induced Variations in the Cultural Characters of 



B. coli: M. R. Smiknow. 



The same technique that was used in the ex- 

 periments on chromogenesis was made use of here. 

 In all, 21 different strains of the various bacilli 

 of the colon-typhoid group were used, but this re- 

 port is confined only to the B. coli, of which seven 

 different strains were experimented on. All of 

 these strains were obtained from the Museum of 

 Natural History of New York through the kind- 



ness of Dr. C.-E. A. Winslow, and were the stock 

 Nos. 19, 44, 45, 46, 52, 57 and 95. The trans- 

 planting was carried out every three or four days 

 over periods varying from one to three months, 

 thus allowing from ten to thirty or more trans- 

 fers. The results obtained in each set of experi- 

 ments were rather constant, though not altogether 

 so, inasmuch as some of the strains reacted quicker 

 or different in the degree of the action at one time 

 than another. 



Control cultures were carried on in plain broth 

 throughout the experiment. It might be stated at 

 once that there were very slight variations between 

 the original stocks and these control cultures, but 

 no more than would be expected as normal varia- 

 tions. These were seen as slightly increased or de- 

 creased amounts of gas or acid formation, in time 

 of coagulation, or slight changes in the growth 

 on potato. At no time, however, were the biolog- 

 ical characters markedly changed nor enzyme pro- 

 duction completely inhibited simply by continual 

 passage through broth. 



Growth on Pototo.— Dextrose seemed to have 

 a special effect upon the character of growth of 

 B. coli on this medium. Five of the seven strains 

 showed at best only a slight yellow or a very light 

 brownish growth on ordinary potato, with prac- 

 tically no discoloration of the medium. Very fre- 

 quently, indeed, the dextrose-affected organisms 

 would give the typical "invisible" growth seen 

 with the B. typhosus. Both the original stock 

 and the control showed the characteristic colon 

 growth on this medium. This change was noted 

 so many times that the explanation based on dif- 

 ferences in the composition of the potato could be 

 excluded. Three of these five strains also showed 

 this change after exposure to phenol. One strain 

 of the B. coli, not changed in this respect with 

 either dextrose or phenol, showed this same varia- 

 tion after growing in either sodium chloride or 

 sodium sulphate broth. 



Action in Milk. — Both phenol and dextrose di- 

 minished the acid production and inhibited the 

 formation of lab enzyme in three of the seven 

 strains of the B. coli, either entirely or for a 

 period of two weeks at least. These results were 

 not seen with the use of the strong saline or 

 sodium sulphate broth. 



Fermentation of Sugars. — The results obtained 

 with these substances on B. coli with reference to 

 variations in sugar fermentations can be best seen 

 in the accompanying charts. The most striking 

 changes here also were seen in those organisms 



