Studies on Azotobacter Chroococcum Beij.
نویسنده
چکیده
The study of the metabolism of Azotobacter has been generally approached from the standpoint of the r6le of this organism in the nitrogen cycle in Nature, but the fact that the ability to fix free nitrogen is regulated by the presence or absence of combined nitrogen in the medium has not been given serious attention although it is made plain in the works to be cited. Bejierink and Van Delden (1902) have shown that Azotobacter chroococcum possesses the power to transform nitrates directly into ammonia and Lipman (1903), Stoklasa (1908), Stranak (1909) and Heinze (1906) found that small quantities of nitrates "stimulated" nitrogen fixation by this organism. If the property of nitrogen fixation were a function of the normal life cycle, it seems strange that, although of vital importance, it should be overcome with such facility. In this connection the data presented by Hills (1918) are most instructive. The accompanying table is a recalculation of the data given by him on pages 200203 of his contribution, and is chosen as it is the only one given which was obtained by the use of a synthetic medium. From this compilation we see that in presence of abundant stores of nitric nitrogen Azotobacter does not fix atmospheric nitrogen but assimilates the nitrogen of the nitrates. A close study of the original data shows that in the presence of ammonium nitrate the organism has a preference for the nitrate radicle leaving the ammonium radicle untouched.
منابع مشابه
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ورودعنوان ژورنال:
- Journal of bacteriology
دوره 6 3 شماره
صفحات -
تاریخ انتشار 2003