128 CHEMISTRY OF BACTERIA AND THEIR PRODUCTS 



faulty because of our slight knowledge of the chemistry of the 

 process, that of Migula seems the best ; it is based on the solu- 

 bility of the pigments formed, as follows : 



(1) Pigments Soluble in Water. This includes the pig- 

 ments of all fluorescent bacteria, as well as those giving a red 

 or brown color to gelatin media. Most important among these 

 is Bacillus pyocyaneus, whose pigments have been considerably 

 studied. There seem to be two pigments, one, pyocyanin, 

 characteristic for this organism ; and a fluorescent pigment 

 which numerous other organisms also produce. Pyocyanin has 

 been analyzed by L/edderhose, who found it to be a ptomam- 

 like body, a derivative of the aromatic series, probably related 

 to the anthracenes. It can be reduced to a colorless letico-base, 

 in which form it is probably produced by the bacteria, and then 

 is oxidized in the air into the pigment. Its composition is 

 C 14 H U N 2 O (the sulphur-containing pyocyanin which has been 

 described is probably impure). The fluorescent pigment is 

 insoluble in alcohol and chloroform, and can thus be separated 

 from pyocyanin, which is soluble in chloroform. Although 

 related to the ptomai'ns, pyocyanin seems to be altogether non- 

 poisonous to animals. 



Jordan 1 and Sullivan 2 have studied the conditions under 

 which pigments are formed, and found that pyocyanin can be pro- 

 duced in proteid-free media, and without the presence of either 

 phosphates or sulphates ; but both sulphur and phosphorus 

 must be present to produce the fluorescent pigment. As pig- 

 ments can be produced on media containing ammonium salts of 

 succinic, lactic, or aspartic acid, or asparagin, they are evidently 

 formed synthetically, and not by cleavage of the media. 



(2) Pigments Soluble in Alcohol and Insoluble in Water. 

 The most important bacteria of this group are the Staphylo- 

 coccus pyogenesaureus and citreus. Their pigment is of a fatty 

 nature, a lipochrome, which lies among the bacteria in the form 

 of dendritic crystals. Being a fat, it can be saponified, and 

 when decomposed it gives the acrolein reactions and odor, from 

 the breaking down of the glycerin of the fat molecule. Acted 

 upon by strong sulphuric acid, the yellow pigment changes into 

 blue granules and crystals (Jipocyanin reaction). The lipo- 

 chromes are soluble in the usual fat solvents, and form fat spots 

 on paper. 



(3) Pigments Insoluble in Water and in Alcohol. The 

 pigment of Micrococcus cereus flavus belongs to this class ; its 

 nature is quite unknown. 



Uour. Exper. Med., 1899 (4), 627. 2 Loc. cif. 



