30 



by a high temperature without interfering with the luxuriance of 

 development. White light had a limiting, red light very little effect 

 upon the pigment; lack of oxygen and also pure oxygen were both 

 detrimental 1 ). Galeotti thus concluded 1) that the power of 

 chroinogenesis in bacteria is not connected indissolubly with the life 

 of those bacteria; such microorganisms may be able to live without 

 producing their characteristic pigment. 2) that the conditions of life 

 which affect the chromogenic power are generally those which have 

 an unfavorable influence upon the bacteria themselves in all their 

 functions. 3) that, given conditions unfavorable to the production 

 of pigment by any special chroraogenic microorganism, that organism 

 will, in a longer or shorter period of time, reacquire the power of 

 pigment production by adapting itself to the unfavorable conditions. 



G a 1 e o 1 1 i ' s first conclusion is supported by most investigators 

 of bacterial chromogenesis, and by all the observations which are here 

 cited as to the ease with which the power of pigment production is 

 lost by some microorganisms. His second and third generalizations 

 are, however, debatable. 



Noesske (18) says, speaking of B. pyocyaneus and 

 B. prodigiosus, "Nicht trotz, sondern infolge zu uppiger 

 Vegetationsbedingungen sistiert mauchmal die Farbstoffbildung auf 

 unserer gebrauchlichen Bouillon." Noesske is supported by 

 Wool ley (21), who concludes that B. pyocyaneus, B. jan- 

 thinus, and B. prodigiosus show better development but less 

 pigment in sugar media as compared with sugar free media; pig- 

 ment is produced more easily in 1 / than in 2 / sugar media, 

 with the exception of B. prodigiosus, which is alike in both 

 cases, but better in glucose than in lactose or saccharose. 



The presence of sugar in nutritive media was, according to 

 Wasserzug, detrimental to the pigment production of B. pro- 

 digiosus; but Laurent (57) found that the influence of sugar 

 could be counteracted by the addition of alkali, i. e., that the in- 

 jurious effect was only indirect, through the acid formed from the 

 sugar by the bacteria. 



Although no very definite conclusions can be drawn from media 

 containing so many unknown elements as our ordinary bouillon or 

 agar, a few preliminary experiments were made with agar as to the 

 effect following on the elimination of some of its constituents. Cul- 

 tures which had been 4 months on neutral sugar -free agar were 

 transferred to similar fresh agar slant tubes. After rejuvenation by 

 the bouillon, gelatin, and agar plate method, sugar -free and 1 



1) cf. Pfeffer, W. Ber. der Kgl. Sachs. Gesellsch. d. Wissensch. Leipzig, 

 math.-phys. Klasse. 1896, p. 379, re Baumgartens Jahresb. 1896, p. 705. 

 ,,Farbstoffbildende Bakterien verraogen den Sauerstoff locker zu binden (ahnlich 

 wie das Hamoglobin) und ihn im sauerstofffreien Raum wieder abzugeben. Der 

 Trager dieser Erscheinung ist der Farbstoff, der die gleiche Wirkung auch iso- 

 liert im alkoholischen Extrakt zeigt, wahrend bei farblosen Bakterien em Gleiches 

 noch nie beobachtet ist. Die Farbstoffbildung, die bisher mehr als eine Luxus- 

 produktion erscheint, erscheint hiernach vieljeicht in einem fiir die Art un- 

 gleich zweckmassigeren Sinne, indem sie vielleicht die Bedeutung hat, dem betr. 

 Bakterium eine stete bereite Sauerstoffreserve zu sichern." 



