76 MICRO-ORGANISMS AND FERMENTATION. 



production of gas and acid. The fungus secretes an enzyme 

 which inverts cane-sugar; but no other enzymes could be 

 detected. 



Especially characteristic of this fungus is its power of 

 resisting elevated temperatures, the younger growths pos- 

 sessing this power in a higher degree than older cultures. 



It is also remarkable that the growth and fermentative 

 action of the fungus are very favourably affected by the 

 presence of considerable quantities of calcium chloride. 



6. BACTERIA EXERCISING AN INVERTING, DIASTATIG, OR 

 PEPTONISING ACTION. 



Bacteria play a very great part in the formation of soluble 

 chemical ferments. This constitutes one of the chief means 

 by which these organisms exercise such an important activity 

 in the economy of nature. 



According to statements made by Hansen, many species 

 of the bacteria which generally occur in beer secrete invertive 

 ferments. Amongst these species are a number of bacteria 

 which exhibit an invertive action in a pure cane-sugar 

 solution but lose this property when yeast-water is added. 

 Similar properties were observed by Wortmann in the case 

 of bacteria which develop diastatic ferments. He found these 

 on putrefying beans and potatoes, and grew the cultures in 

 mixtures of nutritive salts and wheat-starch. Marcano also 

 found a species which exercises diastatic action and which 

 frequently occurs in the outer envelope of maize. Peters 

 found a bacillus in leaven which brought about the solution 

 of starch. In ordinary gelatine-plate cultures this fungus 

 forms peculiar curved colonies, consisting of long filaments 

 about 0-5 p- thick ; in young colonies the filaments are shorter 

 and motile. In beer-wort the bacillus forms rods which 

 exhibit very active movements, and which gradually produce 

 a film on the surface. The spores are rod-like, and their 

 highly refractive contents are for the most part situated at 

 the ends. 



