356 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Stutzer states that his hypomicrobium grows in a mineral solution, and 

 needs carbonic acid for its nutrition, yet possesses no nitrifying power ; 

 its source of energy requires explanation. 



" The refusal of the nitrifying organisms to grow on gelatin and on 

 most organic media is well known. Winogradsky and Omeliansky have 

 lately studied the influence of various kinds of organic matter on the 

 nitrifying process. The presence of • 5 of glucose in 1000 of liquid is 

 sufficient to retard the action of both the nitrous and nitric organisms, 

 while about 2 per 1000 entirely prevents nitrification. Glucose has thus 

 as great an influence upon the nitrifying organisms as phenol has on 

 ordinary bacteria. Of simpler forms of organic matter, as sodium 

 acetate, a much larger quantity is required to hinder nitrification. 



" The influence of ammonia in preventing the action of the nitric 

 organism is very remarkable ; 5 parts per million was sufficient to retard 

 its action, and 150 parts per million prevented it altogether, a proportion 

 which is comparable with an effective dose of mercuric chloride. It 

 seems, however, probable that an increase in the quantity and energy of 

 the nitric organism enables it to bear a somewhat greater quantity of 

 ammonia. 



" It appears from careful trials that the nitrifying organisms are 

 without action upon nitrogenous organic matter ; even methylamine is 

 unaffected by them. For nitrification of organic matter to take place, 

 the aid of other organisms is necessary to decompose it and bring the 

 nitrogen into the form of ammonia. The behaviour of the nitrifying 

 organisms towards organic matter and ammonia is of great practical 

 importance." 



Lactic Acid Ferments and Cheese Ripening.* — MM. Ed. von 

 Freudenreich and O. Jensen record a series of elaborate experiments on 

 the relation between lactic acid ferments and the ripening of Emmen- 

 thal cheese. Their main conclusions are that Tyrothrix bacilli have no 

 share in the ripening of Emmenthal cheese. They do not multiply in 

 normal cheese, and even when added in large numbers to the cheese, 

 exert no influence on the formation of decomposition products. On the 

 flavour of cheese their influence is entirely harmful. The chief share in 

 the ripening of Emmenthal cheese is taken by lactic acid ferments, which 

 increase with great rapidity, render the casein in the cheese soluble, and 

 generate the products characteristic of cheese ripening. It is not im- 

 probable that the natural milk enzymes discovered by Babcock and 

 Russell f participate in the ripening, since, by solubilising the casein, they 

 facilitate the operations of the lactic acid ferments. Pasteurisation of 

 milk, at any rate so far as Emmenthal cheese is concerned, deteriorates 

 the quality of the cheese. The observations show that a loss in the 

 soluble constituents of cheese occurs during ripening, and also indicate 

 the presence of lecithin and traces of glycerophosphoric acid. 



Fermentation of Galactose. J — The researches of M. F. Dienert on 

 the fermentation of galactose and the accustoming of yeasts to this sugar 

 may be summarised as follows. Galactose is a fermentable sugar when 

 a yeast has become accustomed i,o it. The duration of the acclimatisa- 



* Centralbl. Bakt. u. Par., 2" Abt., vi. (1900) pp. 12-6, 38-45,72-9, 112-9, 140-7. 



+ Of. this Journal, 1899, p. 525. 



t Ann. Inst. Pasteur, xiv. (1900) pp. 139-89. 



