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The Nature and Amount of Extracellular Nitrogen in Azotobacter Cultures
Author(s) -
Horner C. Kenneth,
Burk Dean
Publication year - 1940
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1940.036159950004000c0064x
Subject(s) - azotobacter , chemist , chemistry , citation , library science , computer science , organic chemistry , biology , genetics , bacteria
C. KENNETH HORNER AND DEAN BURK A STUDY was made of the amount, proportion • * » • and kind of nitrogen present in the supernatant cell-free liquid from centrifuged pure cultures of a variety of strains and species of Azotobacter. The influence of such culturing variables as age, aeration, nature and concentration of energy source, nitrogen supply, individual inorganic constituents of the medium and stimulants such as agar were considered. Ten to 25% of the total nitrogen (5-25 mg / 100 cc) in young Azotobacter cultures i to 4 days old, was normally found in soluble, noncellular form. In cultures 1-3 weeks old where the available energy supply had virtually disappeared and some autolysis of cells has occurred, the soluble nitrogen generally increased to 50-70% of the total nitrogen; that is, 12-18 mg N/ioo cc was in the extracellular solution. The excreted nitrogen is practically all organic. Results from the use of several organic nitrogen precipitants and from dialysis experiments indicated that it consists of a heterogeneous mixture ranging from simple compounds to complex proteinaceous material. The more complex type of nitrogenous compounds, i.e., those precipitated by trichloracetic acid showed the greatest increase with age of culture. They formed only 5-15% of the extracellular nitrogen in 2-5 day old cultures but nearly half for 24-day or older cultures. Phosphotungstic acid precipitable nitrogen likewise increased with age of culture but to a smaller degree. Nitrogen 'Contribution from Institut national agronomique de Paris and Ecole nationals d'agriculture de Grignon. Published originally in Trans. Third Com. Int. Soc. Soil Sci., A:i6i-i67. 1939. "Contribution from Bureau of Chemistry and Soils, U. S. Dept. of Agriculture. Published originally in Trans. Third Com. Int. Soc. Soil Sci. A:i68-i74. 1939. Junior Chemist and Chemist, respectively.