The utilization of amino acids for growth and their effects on nitrogen fixation differ greatly among the several strains of each species of Azospirillum spp. that were examined. A. brasiliense grew poorly or not at all on glutamate, aspartate, serine, or histidine as the sole nitrogen and carbon sources. Nitrogen fixation by most A. brasiliense strains was inhibited only slightly even by 10 mM...

A method for estimating denitrification and nitrogen fixation simultaneously in coastal sediments was developed. An isotope-pairing technique was applied to dissolved gas measurements with a membrane inlet mass spectrometer (MIMS). The relative fluxes of three N(2) gas species ((28)N(2), (29)N(2), and (30)N(2)) were monitored during incubation experiments after the addition of (15)NO(3)(-). For...

Using standard thermodynamic data it is shown that the oxidation of glucose by nitrogen to give carbon dioxide and ammonia is an overall reaction that involves a substantial evolution of heat and decrease in free energy. This is not in accordance with literature statements that biological nitrogen fixation is endothermic. In the concluding section a Frost diagram is used to survey the thermodyn...

The impact of increasing anthropogenic atmospheric nitrogen deposition on marine biogeochemistry is uncertain. We performed simulations to quantify its effect on nitrogen cycling and marine productivity in a global 3-D ocean biogeochemistry model. Nitrogen fixation provides an efficient feedback by decreasing immediately to deposition, whereas water column denitrification increases more gradual...

Peatlands cover about 3% of the Earth’s surface and are regarded as a vital carbon (C) pool sink. The formation peatland is supported by continuously supplied nitrogen (N) but sources this N remain unclear. Here, we first review stocks rate they accumulate in peatlands, then present N, especially through biological fixation (BNF). We found that global peatlands store 5.9–25.9 Gt N. In past mill...

The fixation of dinitrogen (N2) and denitrification are two opposite processes in the nitrogen cycle. The former transfers atmospheric dinitrogen gas into bound nitrogen in the biosphere, while the latter returns this bound nitrogen back to atmospheric dinitrogen. It is unclear whether or not these processes are intimately connected in any microbial ecosystem or that they are spatially and/or t...

Crop rotation was practiced in ancient times by alternating the use of leguminous and nonleguminous plants. The basis for the benefit derived from this practice was not understood, but it was observed empirically that crops were improved and the condition of the soil was maintained better with rotation than by continual cropping with nonleguminous plants. Rotation was recognized as good husband...

Recently Phelps and Wilson (1) reported the occurrence of hydrogenase, the enzyme which activates molecular hydrogen, in nitrogen-fixing bacteria. Because HZ specifically inhibits nitrogen fixation by red clover plants inoculated with Rhizobium trijolii as well as by Azotobacter (2,3), possession of hydrogenase by these organisms may be more than merely fortuitous. The possibility must be consi...