ALCOHOL-FORMING BACTERIA. 133 



potassium phosphate, 0-5 gramme of magnesium sulphate, 

 1 gramme of ammonium sulphate or phosphate, and a trace of 

 sodium chloride to 1 litre of water. The fermentation was 

 carried on at 34-35 C. in flasks adapted for the cultivation 

 of anaerobic bacteria. He thus proved that two different 

 fermentations of cellulose are set up, a hydrogen ferment and 

 a methane ferment, and that these are produced by two 

 different species of bacteria. Omelianski separated the two 

 by heating the fermenting material for fifteen minutes to 

 75 C. The hydrogen fermentation then proceeded, whilst 

 before warming the methane fermentation took place. The 

 reason is that the spores of the methane bacteria develop 

 more rapidly than those of the hydrogen bacteria. If the 

 liquid is heated to 75 C. after the germination of the spores 

 of the methane bacteria, the vegetative rods of these 

 bacteria will be killed, and only the spores of the hydrogen 

 bacteria will remain alive and germinate. By repeated 

 infection a microscopically pure growth of one or other 

 species may be obtained. 



The cause of the hydrogen fermentation is a thin bacillus, 

 straight or slightly curved, which forms spherical spores at 

 one swollen end. It is not coloured blue by iodine. The 

 fermentation products consist of fatty acids, carbon dioxide, 

 and hydrogen. The exciter of methane fermentation presents 

 a similar microscopic appearance, but the threads are thinner 

 and the spores smaller. It is not coloured blue by iodine. 

 Its fermentation products consist about half of fatty acids 

 (butyric and acetic acids) and half of carbon dioxide and 

 methane. Other bacteria, and amongst them aerobic species, 

 may ferment cellulose, and even moulds e.g., Botrytis and 

 Cladosporium . 



5. Alcohol-forming Bacteria. 



Quite a number of bacteria produce alcohol amongst their 

 products of fermentation. The first known species was dis- 

 covered by Fitz in a cold extract of hay, and was afterwards 

 more exactly investigated by H. Buchner, and described as Bac. 

 Fitzianus (Fig. 26). It occurs both in coccus and bacillus forms. 

 In a nutrient solution containing glycerine it ferments the 



