The near ubiquitous distribution of nifH genes in sediments sampled from 14 high-temperature (48.0-89.0°C) and acidic (pH 1.90-5.02) geothermal springs in Yellowstone National Park suggested a role for the biological reduction of dinitrogen (N(2)) to ammonia (NH(3)) (e.g. nitrogen fixation or diazotrophy) in these environments. nifH genes from these environments formed three unique phylotypes t...

Plant productivity is predicted to increase in boreal forests owing to climate change, but this may depend on whether N inputs from biological N-fixation also increases. We evaluated how alteration of climatic factors affects N input from a widespread boreal N-fixer, i.e. cyanobacteria associated with the feather moss Pleurozium schreberi. In each of 10 forest stands in northern Sweden, we esta...

Heat evolved by isolated soybean (Glycine max cv Clark) nodules was measured to estimate more directly the metabolic cost associated with the symbiotic N(2) fixation system. A calorimeter constructed by modifying standard laboratory equipment allowed measurement on 1 gram of detached nodules under a controlled gas stream. Simultaneous gas balance and heat output determinations were made.There w...

Biological nitrogen (N) fixation is the primary source of “new” N to unmanaged ecosys­ tems, and recent analyses suggest that terrestrial N inputs via free-living N fixation may be more impor­ tant than previously assumed. This may be particularly true in some tropical rain forests, where free-living fixation could outpace symbiotic N fixation to repre­ sent the dominant source of new N inputs....

Agricultural yields are often limited by nitrogen (N) availability, especially in countries of the developing world, whereas industrialized nations application chemical N fertilizers has reached unsustainable levels that have resulted severe environmental consequences. Finding alternatives to inorganic is critical for sustainable and secure food production. Although gaseous (N2) abundant atmosp...

cyanobacteria were collected and identified in five paddy fields with different soil textures of golestan province in iran. it was determined that nostoc ellipsosporum and nostoc muscorum were dominant in all sites among 20 species. to assess the ability of atmospheric nitrogen fixation by the species, their pure cultures were provided by growing on bg-11 solid culture medium. subsequently, eac...

Grain legumes convert atmospheric N2 to reactive N through symbiosis with N2-fixing rhizobia. Biological N2 fixation associated with legumes and the subsequent decomposition of legume residues are the primary processes that replenish N removed by harvest in agroecosystems without the addition of fertilizer N (Galloway et al., 1995, Peoples et al., 1995). Therefore, legumes are often included in...

In temperate Atlantic waters (18.8 to 20.1°C), biological nitrogen fixation has been demonstrated by 2 independent measurements: N-N2 incorporation and nifH identification in the DNA and expressed messenger RNA (mRNA). At 2 stations in the western English Channel, bulk waters were incubated with N-N2. At the high levels of particulate nitrogen (≤11.5 μmol N l–1), absolute fixation rates of 18.9...

To understand the impact of the northwestern Azores Current Front (NW-AzC/AzF) system on HCO3--and N2-fixation activities and unicellular diazotrophic cyanobacteria (UCYN) distribution, we combined geochemical and biological approaches from the oligotrophic surface to upper mesopelagic waters. N2-fixation was observed to sustain 45-85% of the HCO3--fixation in the picoplanktonic fraction perfor...