Mechanisms of increased Trichodesmium fitness under iron and phosphorus co-limitation in the present and future ocean.

Nathan G Walworth,Dawn Moran,Matthew R Mcllvin,Mak A Saito,Michael D Lee,Fei-Xue Fu,Eric A Webb,David A Hutchins

doi:10.1038/ncomms12081

Nathan G Walworth, Dawn Moran + Show 6 more

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https://doi.org/10.1038/ncomms12081

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Abstract

Nitrogen fixation by cyanobacteria supplies critical bioavailable nitrogen to marine ecosystems worldwide; however, field and lab data have demonstrated it to be limited by iron, phosphorus and/or CO2. To address unknown future interactions among these factors, we grew the nitrogen-fixing cyanobacterium Trichodesmium for 1 year under Fe/P co-limitation following 7 years of both low and high CO2 selection. Fe/P co-limited cell lines demonstrated a complex cellular response including increased growth rates, broad proteome restructuring and cell size reductions relative to steady-state growth limited by either Fe or P alone. Fe/P co-limitation increased abundance of a protein containing a conserved domain previously implicated in cell size regulation, suggesting a similar role in Trichodesmium. Increased CO2 further induced nutrient-limited proteome shifts in widespread core metabolisms. Our results thus suggest that N2-fixing microbes may be significantly impacted by interactions between elevated CO2 and nutrient limitation, with broad implications for global biogeochemical cycles in the future ocean.

Highlights

Nitrogen fixation by cyanobacteria supplies critical bioavailable nitrogen to marine ecosystems worldwide; field and lab data have demonstrated it to be limited by iron, phosphorus and/or CO2
To begin to address these issues, we examine the cellular responses of Trichodesmium erythraeum strain IMS101 to Fe and/or P-limitation using a global proteomics approach in the context of long-term adaptation to both current CO2 concentrations and projected future ocean acidification conditions[23]
Our results demonstrate a complex response of cellular metabolism specific to Fe/P co-limitation, which includes increased growth rates, broad proteome restructuring and cell size reductions relative to growth limited by a single nutrient

Summary

Introduction

Nitrogen fixation by cyanobacteria supplies critical bioavailable nitrogen to marine ecosystems worldwide; field and lab data have demonstrated it to be limited by iron, phosphorus and/or CO2. Our results demonstrate a complex response of cellular metabolism specific to Fe/P co-limitation, which includes increased growth rates, broad proteome restructuring and cell size reductions relative to growth limited by a single nutrient.

Results

Conclusion