منابع مشابه
Evolution: A Fixed-Nitrogen Fix in the Early Ocean?
A new study asserts that a late evolutionary leap in cyanobacterial nitrogen fixation terminated a long history of nitrogen-limited primary production in the ocean--and contributed to a dramatic increase in biospheric oxygen coincident with the rise of animals.
متن کاملStreptomyces thermoautotrophicus does not fix nitrogen.
Streptomyces thermoautotrophicus UBT1 has been described as a moderately thermophilic chemolithoautotroph with a novel nitrogenase enzyme that is oxygen-insensitive. We have cultured the UBT1 strain, and have isolated two new strains (H1 and P1-2) of very similar phenotypic and genetic characters. These strains show minimal growth on ammonium-free media, and fail to incorporate isotopically lab...
متن کاملSanctions and mutualism stability: why do rhizobia fix nitrogen?
Why do rhizobia expend resources on fixing N(2) for the benefit of their host plant, when they could use those resources for their own reproduction? We present a series of theoretical models which counter the hypotheses that N(2) fixation is favoured because it (i) increases the exudation of useful resources to related rhizobia in the nearby soil, or (ii) increases plant growth and therefore th...
متن کاملMutants of azotobacter that do not fix nitrogen.
Stable strains of mutants of Azotobacter that do not fix nitrogen are difficult to obtain by traditional procedures (Karlsson and Barker, 1948; Lindstrom, 1948). Stumbo and Gainey (1938) demonstrated that culturing Azotobacter on a high nitrate medium resulted in strains that failed to fix nitrogen even after continued transfer in the absence of fixed nitrogen. However, since these strains were...
متن کاملMATERIALS CHEMISTRY COMMUNICATION Nitrogen-containing carbon nanotubes
could be prepared by employing appropriate precursor molecules. Nanotubes containing both boron and nitrogen have Carbon nanotubes containing small amounts of nitrogen are been grown in the electric arc discharge between graphite produced by the pyrolysis of aza-aromatics such as pyridine, cathodes and graphite anodes filled with boron in a nitrogen methylpyrimidine and triazine over cobalt nan...
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ژورنال
عنوان ژورنال: Science
سال: 2003
ISSN: 0036-8075,1095-9203
DOI: 10.1126/science.300.5617.215a