Urease as a product of Bacterium radicicola. 



Nature, London, Vol. 1 12, 1923, p. 439. 



The letter by Prof. Werner in Nature of August 1 1 ,,On the Presence of 

 Urease in the Nodules of the Roots of the Leguminous Plants", induces me to 

 state that urease is also produced by the pure cultures of Bacterium radicicola, and 

 much more profusely than by the nodules. Such forms as Viciae, Trifolii, Pisi, are 

 particularly strong in this respect, while Ornitliopodis and Litpini are but feeble 

 ureaseproducers. 



It is interesting to observe that urease is also, in certain cases, a product of the 

 normal papilionaceous plants, first discovered by Takeuchi in the beans of 

 Soja hispida, and by me in the seeds and the rind of the branches of Cytisns Laburnum 

 and Glycine chinensis. 



The simplest way for the demonstration of the enzyme is the plate-method 

 which I have described in Centralblatt f. Bakt. 2te Abt., Bd. 5, p. 323, 1893, and 

 Archives Neerlandaises, 1895 l ). As, however, B. radicicola does not grow well on 

 broth-gelatin, or yeast-decoct-gelatin with l'/2% urea, the detection of the enzyme 

 must be made with material taken from colonies previously grown on peas-leaf- 

 gelatin, with 2% cane-sugar, and then used as little lumps, placed on the yeast- 

 decoct-urea-gelatin plate. After a few minutes the beautiful , .iris-phenomenon" 

 becomes visible if urease is present, as a consequence of the production of ammonium- 

 carbonate which precipitates the calcium-carbonate and calcium-phosphate in the 

 particular manner proper to this experiment. The addition of some calcium-malate to 

 the yeast-urea-gelatin enhances the sensibility of the iris-reaction. 



The discovery of urease in B. radicicola was the result of experiments on the 

 nutrition of this bacterium, performed in 1919 and 1920, with the cooperation of Mr. 

 Ir. L. E. den Dooren de Jong at Delft. 



Gorssel, Holland. 



i) These references are incorrect and should read: Centr. bl. Bakt. Abt. II Bd. VII, 

 , p. 23 61; Arch. Ne'erl. Ser. II T. VII, igo2, p. 28 63; the latter paper can also be 

 found in: Verzamelde Geschriften, Vol. IV, p. 78. (Editors). 



20 



