Bacteriologie. 143 



Hoffmann, C. and B. W. Hammer. So me factors concern ed 

 in the fixation ofnitrogen by iVzotobacter. (Chi. Bakt. 2. 

 XXVIII. p. 127-139. 1910.) 



The results of this papers are: Different soils vary widely in 

 their power to fix atmospheric nitrogen, a ränge from 0,15 to 

 14,47 mgr of N per gr. of mannit consumed having been obtained 

 with the soils studied. Mannit and lactose are to be regarded 

 as the best sugars for maximum fixation in impure cultures. Mal- 

 tose and sucrose in impure cultures gave but slight fixations. 

 Under pure culture conditions mannit and dextrin yielded the best 

 results. Sucrose, which gave but slight fixation in impure cultures, 

 gave a high degree with a pure culture. Lactose showed a less 

 degree of fixation in pure than in impure cultures. Smaller quan- 

 tities of carbohydrates in the culture Solution tend to enhance 

 the activity of azotobacter. Di- and tri-calcium phosphates 

 give better results as regards fixation than the mono salt. In deter- 

 mining the coefificient of nitrogen fixation of any soil it is important 

 to consider the period of incubation. If this is too long, losses in 

 the nitrogen fixed will result and determinations of the nitrogen 

 content of the cultures will not be a true index of the actual 

 amount fixed. From the results obtained it would seem that the 

 period of incubation for impure cultures should ränge from 21 to 

 28 days. CaCOg need be present in but very small quantities No 

 increase in fixation was observed from an increase in the amount 

 of CaCOg in the culture Solution. For abundant development in pure 

 culture when grown in liquid media, the use of a quartzsand slope 

 as described has proven very efficient. To secure an abundant 

 supply of the dry azotobacter cells, for chemical analysis the use 

 of the large Petri dish-cultures as described, is to be recommen- 

 ded. The protein content of the cells of azotobacter as determined 

 is apparently influenced by the age of the cultures. The percentage 

 of protein o"btained ranged from 8,31% to 19,13^/0. These results 

 are considerably below those secured by other investigators. The 

 method of cultivation used may be a possible explanation of this 

 difference. The phosphorus content of the cells is also inüuenced 

 by the age of the culture. The amount of P calculated as P2O5 

 ranged from 2,51o/o to 2,970/o. Matouschek (Wien). 



Wagner, R. J., Wasserstoffionen -Konzentration und 

 natürliche Immunität der Pflanzen. [V.M.]. (Cbl. Bakt. 

 2. XLIV. p. 708—719. 7 K. 1915.) 



Verfasser injizierte Sinapis alba, Brassica, Knollen der Kartoffel 

 {Solajium tuberosum) und Sempervivum Hausmannii mit Pseudomo- 

 nas campestris (Sinapis), Bac. phytophthorus {Solanum) und Bac. 

 vulgatus [Sempervivum). Die Bakterienmenge betrug 830. Bac. bei 

 Sinapis und Brassica, bezw. 420, ca. 1000 bei der Kartoffel und 

 1500—3000 bei Sempervivum. Es Hess sich deutlich eine Inkubations- 

 zeit unterscheiden, die 4—6 Tage dauert. Innerhalb der Beobach- 

 tungszeit (12 Tage) traten starke Aenderungen der H lonenkonzen- 

 tration ein, welche eine Reaktionserscheinung auf die Injektion 

 phytopathogener Bakterien sind. Sofort nach der Injektion tritt eine 

 Verringerung der Azidität auf. Gleichzeitig mit dem Auftreten der 

 ersten Krankheitssymptome steigt die Azidität um 2—3 Zehntel 

 PH. Ist die Pflanze imstande, sich der Bacterien zu erwehren, so 



