Herbivory by an invasive snail increases nitrogen fixation in a nitrogen-limited stream

2009 ◽  
Vol 66 (8) ◽  
pp. 1309-1317 ◽  
Author(s):  
Clay Porter Arango ◽  
Leslie Anne Riley ◽  
Jennifer Leah Tank ◽  
Robert Ogden Hall,
Keyword(s):  
Nitrogen Fixation ◽  
New Zealand ◽  
Nitrogen Cycling ◽  
Algal Biomass ◽  
Nitrogen Fixing ◽  
Nitrogen Flux ◽  
Future Studies ◽  
Nitrogen Fixers ◽  
Heavy Grazing ◽  
Anthropogenic Nitrogen

Despite anthropogenic nitrogen contributions, nitrogen fixation contributes half of biosphere inputs but has rarely been quantified in streams. Herbivory controls algal biomass and productivity in streams, and we hypothesized that herbivory could also control nitrogen fixation. We released periphyton from herbivory in nitrogen-limited Polecat Creek, Wyoming, where heavy grazing by the invasive New Zealand mudsnail ( Potamopyrgus antipodarum ) dominates nitrogen cycling. One and two weeks after releasing periphyton, we found higher rates of nitrogen fixation on heavily grazed rocks (two-way analysis of variance (ANOVA), p = 0.012). Time elapsed after snail manipulation had no effect (two-way ANOVA, p = 0.24). Grazing changed periphyton composition by reducing the proportion of green algae and increasing the proportion of nitrogen-fixing diatoms (multivariate ANOVA, p = 0.001). Nitrogen fixation rates increased disproportionately to nitrogen-fixing algal cells, indicating that snails increased nitrogenase efficiency, probably by improving light and (or) nutrient availability to nitrogen fixers. We incorporated our nitrogen fixation rates into a published nitrogen budget for Polecat Creek and found that nitrogen flux into the periphyton was 50% higher when we included nitrogen fixation. Herbivory can increase nitrogen fixation in streams, and future studies should measure nitrogen fixation for a more thorough understanding of stream nitrogen cycling.

scholarly journals The Nodule Microbiome: N2-Fixing Rhizobia Do Not Live Alone

2017 ◽  
Vol 1 (2) ◽  
pp. 70-82 ◽  
Author(s):  
Pilar Martínez-Hidalgo ◽  
Ann M. Hirsch
Keyword(s):  
Nitrogen Fixation ◽  
Environmental Stress ◽  
Host Plant ◽  
Diverse Population ◽  
Nitrogen Fixing ◽  
Chemical Fertilizers ◽  
Associated Bacteria ◽  
Culture Techniques ◽  
Nitrogen Fixers

For decades, rhizobia were thought to be the only nitrogen-fixing inhabitants of legume nodules, and biases in culture techniques prolonged this belief. However, other bacteria, which are not typical rhizobia, are often detected within nodules obtained from soil, thus revealing the existence of a phytomicrobiome where the interaction among the individuals is not only complex, but also likely to affect the behavior and fitness of the host plant. Many of these nonrhizobial bacteria are nitrogen fixers, and some also induce nitrogen-fixing nodules on legume roots. Even more striking is the incredibly diverse population of bacteria residing within nodules that elicit neither nodulation nor nitrogen fixation. Yet, this community exists within the nodule, albeit clearly out-numbered by nitrogen-fixing rhizobia. Few studies of the function of these nodule-associated bacteria in nodules have been performed, and to date, it is not known whether their presence in nodules is biologically important or not. Do they confer any benefits to the Rhizobium-legume nitrogen-fixing symbiosis, or are they parasites/saprophytes, contaminants, or commensals? In this review, we highlight the lesser-known bacteria that dwell within nitrogen-fixing nodules and discuss their possible role in this enclosed community as well as any likely benefits to the host plant or to the rhizobial inhabitants of the nodule. Although many of these nodule inhabitants are not capable of nitrogen fixation, they have the potential to enhance legume survival especially under conditions of environmental stress. This knowledge will be useful in defining strategies to employ these bacteria as bioinoculants by themselves or combined with rhizobia. Such an approach will enhance rhizobial performance or persistence as well as decrease the usage of chemical fertilizers and pesticides.

scholarly journals Transcriptional Activities of the Microbial Consortium Living with the Marine Nitrogen-Fixing Cyanobacterium Trichodesmium Reveal Potential Roles in Community-Level Nitrogen Cycling

2017 ◽  
Vol 84 (1) ◽  
Author(s):  
Michael D. Lee ◽  
Eric A. Webb ◽  
Nathan G. Walworth ◽  
Fei-Xue Fu ◽  
Noelle A. Held ◽  
...  
Keyword(s):  
Gene Expression ◽  
Nitrogen Fixation ◽  
Microbial Communities ◽  
Nitrogen Cycling ◽  
Carbon Fixation ◽  
Community Respiration ◽  
Ecological Niches ◽  
Nitrogen Fixing ◽  
Content Type ◽  
Globally Distributed

ABSTRACTTrichodesmiumis a globally distributed cyanobacterium whose nitrogen-fixing capability fuels primary production in warm oligotrophic oceans. Like many photoautotrophs,Trichodesmiumserves as a host to various other microorganisms, yet little is known about how this associated community modulates fluxes of environmentally relevant chemical species into and out of the supraorganismal structure. Here, we utilized metatranscriptomics to examine gene expression activities of microbial communities associated withTrichodesmium erythraeum(strain IMS101) using laboratory-maintained enrichment cultures that have previously been shown to harbor microbial communities similar to those of natural populations. In enrichments maintained under two distinct CO2concentrations for ∼8 years, the community transcriptional profiles were found to be specific to the treatment, demonstrating a restructuring of overall gene expression had occurred. Some of this restructuring involved significant increases in community respiration-related transcripts under elevated CO2, potentially facilitating the corresponding measured increases in host nitrogen fixation rates. Particularly of note, in both treatments, community transcripts involved in the reduction of nitrate, nitrite, and nitrous oxide were detected, suggesting the associated organisms may play a role in colony-level nitrogen cycling. Lastly, a taxon-specific analysis revealed distinct ecological niches of consistently cooccurring major taxa that may enable, or even encourage, the stable cohabitation of a diverse community withinTrichodesmiumconsortia.IMPORTANCETrichodesmiumis a genus of globally distributed, nitrogen-fixing marine cyanobacteria. As a source of new nitrogen in otherwise nitrogen-deficient systems, these organisms help fuel carbon fixation carried out by other more abundant photoautotrophs and thereby have significant roles in global nitrogen and carbon cycling. Members of theTrichodesmiumgenus tend to form large macroscopic colonies that appear to perpetually host an association of diverse interacting microbes distinct from the surrounding seawater, potentially making the entire assemblage a unique miniature ecosystem. Since its first successful cultivation in the early 1990s, there have been questions about the potential interdependencies betweenTrichodesmiumand its associated microbial community and whether the host's seemingly enigmatic nitrogen fixation schema somehow involved or benefited from its epibionts. Here, we revisit these old questions with new technology and investigate gene expression activities of microbial communities living in association withTrichodesmium.

NON-SYMBIOTIC NITROGEN FIXATION IN SOME QUEBEC SOILS

1965 ◽  
Vol 11 (1) ◽  
pp. 29-38 ◽  
Author(s):  
P-C. Chang ◽  
R. Knowles
Keyword(s):  
Nitrogen Fixation ◽  
Symbiotic Nitrogen Fixation ◽  
Soil Types ◽  
Anaerobic Incubation ◽  
Nitrogen Fixing ◽  
Free Living ◽  
Aerobic Conditions ◽  
Bacterial Counts ◽  
Facultatively Anaerobic ◽  
Nitrogen Fixers

The occurrence of free-living nitrogen fixers, the potential for nitrogen fixation, and the correlation between the nitrogen-fixing capacities of the soils and bacterial counts were studied using representative Quebec soils.Clostridium occurred more frequently than did Azotobacter. Studies with N15showed that nitrogen fixation was more frequent under anaerobic than under aerobic conditions in all the soil types studied in their unamended state. The addition of glucose stimulated nitrogen fixation. During anaerobic incubation, nitrogen fixation was found to be correlated significantly with the increase in numbers of both total aerobes and Clostridia. The results suggested that facultatively anaerobic nitrogen fixers, and aerobic nitrogen fixers other than Azotobacter, were present.

scholarly journals Complete Genome Sequences of Trifolium spp. Inoculant Strains Rhizobium leguminosarum sv. trifolii TA1 and CC275e: Resources for Genomic Study of the Rhizobium-Trifolium Symbiosis

2020 ◽  
pp. MPMI-08-20-0220
Author(s):  
Benjamin J. Perry ◽  
Shaun Ferguson ◽  
Aurelie Laugraud ◽  
Steve A. Wakelin ◽  
Wayne Reeve ◽  
...  
Keyword(s):  
New Zealand ◽  
Open Access ◽  
Complete Genome ◽  
Rhizobium Leguminosarum ◽  
Nitrogen Fixing ◽  
Genome Sequences ◽  
Future Studies ◽  
Genomic Study ◽  
Commercial Inoculant ◽  
Open Access Article

Rhizobium leguminosarum symbiovar trifolii strains TA1 and CC275e are nitrogen-fixing microsymbionts of Trifolium spp. and have been used as commercial inoculant strains for clovers in pastoral agriculture in Australia and New Zealand. Here we present the complete genome sequences of both strains, resolving their multipartite genome structures and allowing for future studies using genomic approaches. [Formula: see text] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .

scholarly journals Ancient CO2 levels favor nitrogen fixing plants over a broader range of soil N compared to present

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Haoran Chen ◽  
John Markham
Keyword(s):  
Nitrogen Fixation ◽  
Plant Biomass ◽  
Betula Papyrifera ◽  
Soil N ◽  
Nitrogen Fixing ◽  
N Level ◽  
Nitrogen Fixers ◽  
Alnus Viridis ◽  
Nitrogen Concentrations ◽  
Different Levels

AbstractSmall inreases in CO2 stimulate nitrogen fixation and plant growth. Increasing soil N can inhibit nitrogen fixation. However, no studies to date have tested how nitrogen fixing plants perform under ancient CO2 levels (100 MYA), when nitrogen fixing plants evolved, with different levels of N additions. The aim of this study was to assess if ancient CO2, compared to present, favors nitrogen fixers over a range of soil nitrogen concentrations. Nitrogen fixers (Alnus incana ssp. rugosa, Alnus viridis ssp. crispa, and Alnus rubra) and their close non-nitrogen fixing relatives (Betula pumila, Betula papyrifera, Betula glandulosa) were grown at ancient (1600 ppm) or present (400 ppm) CO2 over a range of soil N levels, equivalent to 0, 10, 50, and 200 kg N ha−1 year−1. The growth of non-N fixing plants increased more than N fixing plants in response to the increasing N levels. When grown at an ancient CO2 level, the N level at which non-nitrogen fixing plant biomass exceeded nitrogen fixing plant biomass was twice as high (61 kg N ha−1 year−1) as the N level when plants were grown at the ambient CO2 level. Specific nodule activity was also reduced with an increasing level of soil N. Our results show there was a greater advantage in being a nitrogen fixer under ancient levels of CO2 compared with the present CO2 level.

scholarly journals Ancient CO2 Levels Favor Nitrogen Fixing Plants Over a Broader Range of Soil N Compared to Present

2020 ◽  
Author(s):  
Haoran Chen ◽  
John Markham
Keyword(s):  
Nitrogen Fixation ◽  
Plant Biomass ◽  
Betula Papyrifera ◽  
Soil N ◽  
Nitrogen Fixing ◽  
N Level ◽  
Nitrogen Fixers ◽  
Alnus Viridis ◽  
Nitrogen Concentrations ◽  
Different Levels

Abstract Small inreases in CO2 stimulate nitrogen fixation and plant growth. Increasing soil N can inhibit nitrogen fixation. However, no studies to date have tested how nitrogen fixing plants perform under ancient CO2 levels (100 MYA) when nitrogen fixers evolved, with different levels of N additions. The aim of this study was to assess if ancient CO2, compared to present, favors nitrogen fixers over a range of soil nitrogen concentrations. Nitrogen fixers (Alnus incana ssp. rugosa, Alnus viridis ssp. crispa, and Alnus rubra) and their close non-nitrogen fixing relatives (Betula pumila, Betula papyrifera, Betula glandulosa) were grown at ancient CO2 (1600 ppm) or present CO2 (400 ppm) over a range of soil N levels, equivalent to 0, 10, 50, and 200 kg N ha-1 year-1. The growth of non-N fixing plants increased more than N fixing plants in response to the increasing N levels. When grown at an ancient CO2 level, the N level at which non-nitrogen fixing plant biomass exceeded nitrogen fixing plant biomass was twice as high (61 kg N ha-1 y-1) as the N level when plants were grown at an ambient CO2 level. Specific nodule activity was also reduced with an increasing level of soil N. Our results showed there was a greater advantage in being a nitrogen fixer under ancient levels of CO2 compared with the present CO2 level.

Nitrogen fixation by soil microorganisms

1928 ◽  
Vol 18 (3) ◽  
pp. 432-438 ◽  
Author(s):  
P. G. Krishna
Keyword(s):  
Nitrogen Fixation ◽  
Organic Acids ◽  
Soil Microorganisms ◽  
Limited Extent ◽  
Nitrogen Fixing ◽  
Optimum Range ◽  
Nitrogen Fixers ◽  
The Media

From the results presented it may be permissible to point out the following:Fungi are responsible for the fixation of very small quantities of nitrogen, while the Azotobacter and B. amylobacter groups are the important nitrogen fixers in the soil.B. amylobacter is able to fix from 4 to 5 mg. of nitrogen per gm. of dextrose consumed.B. amylobacter has an optimum range of pH. between 6·0 and 7·0, and Azotobacter between 7·0 and 8·4.Azotobacter utilises the organic acids produced during the fermentation of dextrose as sources of energy for nitrogen fixation in the absence of dextrose. B. amylobacler does not, or does only to a limited extent, utilise such products.Large quantities of dextrose do not favour an efficient nitrogen fixation, as large quantities of the organic acids produced effect the reaction of the media rendering the organisms inactive.The nitrogen fixing organisms seem to be equally well represented in the heavy and light soils.

scholarly journals Active nitrogen fixation by Crocosphaera expands their niche despite the presence of ammonium – A case study

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Keisuke Inomura ◽  
Takako Masuda ◽  
Julia M. Gauglitz
Keyword(s):  
Nitrogen Fixation ◽  
Mechanistic Model ◽  
Energy Costs ◽  
High Electron ◽  
Nitrogen Fixing ◽  
Active Nitrogen ◽  
State Culture ◽  
Nitrogen Fixers ◽  
Efficient Alternative

Abstract Unicellular nitrogen fixer Crocosphaera contributes substantially to nitrogen fixation in oligotrophic subtropical gyres. They fix nitrogen even when significant amounts of ammonium are available. This has been puzzling since fixing nitrogen is energetically inefficient compared with using available ammonium. Here we show that by fixing nitrogen, Crocosphaera can increase their population and expand their niche despite the presence of ammonium. We have developed a simple but mechanistic model of Crocosphaera based on their growth in steady state culture. The model shows that the growth of Crocosphaera can become nitrogen limited despite their capability to fix nitrogen. When they fix nitrogen, the population increases by up to 78% relative to the case without nitrogen fixation. When we simulate a simple ecological situation where Crocosphaera exists with non-nitrogen-fixing phytoplankton, the relative abundance of Crocosphaera increases with nitrogen fixation, while the population of non-nitrogen-fixing phytoplankton decreases since a larger fraction of fixed nitrogen is consumed by Crocosphaera. Our study quantitatively supports the benefit of nitrogen fixation despite the high electron/energy costs, even when an energetically efficient alternative is available. It demonstrates a competitive aspect of Crocosphaera, permitting them to be regionally significant nitrogen fixers.

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