345 



where ferments moulds, and most l)acteria die alter V- to i hour already, while ihe 

 enzymes in the cells remain unhurt. 



If a small lump of killed microbes is put in an indican-solution, poi!red out to a 

 tliin layer in a white porcelain vessel floating on water of circa 45" C, then only 

 those microbes will become blue, which contain indigo-enzyme, while those, acting by 

 katabolism, don't cause decomposition. If in the latter case not all but only most of 

 the microbes have been killed, there will at first be no manifest decomposition, but 

 it will set in as soon as the living individuals have sufficiently multiplied, which is at 

 the same time a good control of the experiment. 



The microbes containing enzymes can be dried and powdered after killiiig and 

 such »crude enzymes», when kept dry, preserve thejr activity very long. By the little 

 dissolubility of the indigo-enzynies in water, glycerine and salt-solutions, it wis not 

 possible by extracting the crude enzymes and precipitating with alcohol, to obtain 

 more active preparations from them. 



It has been proved that all examined bacteria, blastomycetes ' ) and moulds, which 

 decompose indican, do not effect this by enzymes but by katabolism, while among 

 alcohol-ferments both cases occur. So indican is decomposed katabolically by Sacharo- 

 myces ludwigi and Monilia candida, while Saccharomyces sphaericus*), S. apiculatiis. 

 S. muciparus^), S. tyrocola ') contain indigo-enzymes. One of these enzymes, that of 

 S. sphaericus, which acts the most strongly of all, will be treated in § 6. 



Here I wish to remark that indigo-enzymes originate in the yeast-cells only 

 then, when cultured on a solid medium e. g. on wort-gelatine, with abundant access 

 of air. When cultured in nutriënt liquids, even with a current of air passing through, 

 they produce no or only very little enzyme. 



The indigo-blue, formed by most moulds and yeast-species in the decomposition 

 of indican, is for the greater part confined withiii the protoplasm, as was already 

 described and figured by Mr. Molisch (l.c); but in those cases when decomposition 

 is very strong, as with many bacteria, the indoxyl streams out and also precipitates 

 outside of the cell in granides of indigo-blue. 



5. Indigo-fennentatiun hy Aërobacter. 



When a decoction of Indigofera or Polygonum is infected with-garden-soil, canal- 

 water or mud, and placed at 28° C, there originates, during a copious formation of 

 indigo, a rich bacteria-flora in which the common gas-producing ferments, which I 

 recently united ■'') in the genus Aërobacter, perform the chief part. The first who 



') Blastomycetes have the shape of yeast-cells but produce no alcohol. To these 

 belong e. g. the red »yeats« Blastomyces glutinis, B. roseus, B. granulosus (of which the 

 last colours deep blue with jodine). and which all decompose indican vigorously. 



'-) Under this name. given by Nagcli, T united the various forms of acthyl-acetate 

 yeast. (Verhandelingen 5e Natuur-en Geneeskundig Congres te .\mstcrdam. i8o5. P- 30l-) 



•) This name I give to a saccharose-ycast, very common in prcssed yeast and 

 which does not ferment maltose. 



*) 5. tyrocola is a lactose-yeast. not rare in Edam cheese. lts cultun-s on wort- 

 gelatine are sometiines rose-coloured. 



') Ccntralblatt fiir Bacteriologie. 2e .\bt. Bd. 6 X°. 7. 1900. 



