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Updated: Jan 18, 2026
09:49
Prospecting Microbial Strains for Bioremediation and Probiotics Development for Metaorganism Research and Preservation
Published on: October 31, 2019
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Ecosystem consequences of a nitrogen-fixing proto-organelle
Jane C Marks1,2, Michael C Zampini1,2, Raina Fitzpatrick1,2
1Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011.
Summary
Microbial symbioses are vital for river ecosystems. This study reveals how nitrogen-fixing diatoms and their endosymbionts support food webs by exchanging carbon and nitrogen with algae, enhancing nutrient cycling.
Area of Science:
- Ecology
- Microbiology
- Biogeochemistry
Background:
- Microscale symbioses are crucial for ecosystem functions, but their mechanisms in nature are often unclear.
- River food webs rely on primary producers, with nutrient availability influencing their interactions.
Purpose of the Study:
- To investigate carbon and nitrogen exchanges among symbiotic primary producers in a river ecosystem.
- To quantify organism-specific carbon and nitrogen fixation rates using advanced isotopic techniques.
Main Methods:
- Utilized stable isotope imaging (nanoSIMS) and tracing.
- Employed quantitative stable isotope probing via density centrifugation.
- Analyzed nutrient dynamics and organism-specific fixation rates from subcellular to ecosystem scales.
Main Results:
- Macroalgae *Cladophora glomerata* initially dominates, but epiphytic diatoms *Epithemia* spp. with nitrogen-fixing endosymbionts become crucial during summer.
- Nitrogen fixation rates increased as *Epithemia* spp. dominated, while *Cladophora* carbon fixation decreased.
- Carbon transfer to grazers (caddisflies) was 10-fold higher with high *Epithemia* loads, and endosymbionts showed high carbon and nitrogen accumulation.
Conclusions:
- The tripartite symbiosis significantly enhances nitrogen fixation rates in river ecosystems.
- These microscale interactions are critical for fueling higher trophic levels and nutrient cycling in river food webs.
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