66 ACTIVITIES OF BACTERIA. 



A counterpart to splitting fermentation is the rarer oxi- 

 dation fermentation, of which the most beautiful ex- 

 ample is the formation of acetic acid from alcohol. Here, 

 likewise, there occurs one-sided metabolic activity by the 

 acetic-acid fungus, which obtains a large supply of energy, 

 not through the splitting up of an easily decomposed sub- 

 stance, but through oxidation of resorbed alcohol. The 

 gain of energy is here dependent simply upon a partial de- 

 velopment and enhancement of the ordinary phenomena 

 in the nourishment of bacteria. 1 



According to this, fermentation products as well as all 

 other products of bacterial cells are metabolic products, and 

 a special separate treatment of fermentation is not de- 

 manded. On the contrary, it seems most suitable to ar- 

 range the discussion of the single bacterial products acord- 

 ing to whether they originate in nutrient media which 

 contain sugar, or are free from it, and to add something 

 concerning such activities of bacteria as result in the 

 breaking up of salts of fatty acids, alcohols, etc. 



i. Pigment Production. 



The pigments have been but little studied chemically, 

 yet recently, through several pupils of Migula, at least a 

 provisional survey has become possible. Compare 

 Schneider (A. K. i, 201) and Thumm (A. K. i, 291). 



The red and yellow pigments which have been 

 thoroughly studied are almost all 2 insoluble in water, but 

 soluble in alcohol, ether, carbon bisulphid, benzol, and 

 chloroform. For the present they may be placed in two 

 groups: 



(a) Pigments of the carotin group. Yellow, orange, 

 rose colored, with strong sulphuric acid becoming bluish- 

 green ; with caustic alkalis, orange to red. In some 

 cases the pigments, which often consist of a mixture of 



1 Certainly splitting fermentation is always a restricted, and only 

 under certain circumstances a highly developed, function. 



2 In marked contrast to this are the findings of M. Freund ( C. B. 

 XVI, 640), according to which the red and yellow pigments produced 

 by four newly discovered bacteria were always soluble in water and 

 insoluble in alcohol and ether. 



