Acclimation of Emiliania huxleyi (1516) to nutrient limitation involves precise modification of the proteome to scavenge alternative sources of N and P.

Boyd A Mckew,Christine A Raines,Richard J Geider,Gergana Metodieva,Metodi V. Metodiev

doi:10.1111/1462-2920.12957

Boyd A Mckew, Christine A Raines + Show 3 more

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https://doi.org/10.1111/1462-2920.12957

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Journal: Environmental Microbiology	Publication Date: Aug 17, 2015
Citations: 39	License type: CC BY 4.0

Affiliation: University of Essex

Abstract

SummaryLimitation of marine primary production by the availability of nitrogen or phosphorus is common. E miliania huxleyi, a ubiquitous phytoplankter that plays key roles in primary production, calcium carbonate precipitation and production of dimethyl sulfide, often blooms in mid‐latitude at the beginning of summer when inorganic nutrient concentrations are low. To understand physiological mechanisms that allow such blooms, we examined how the proteome of E . huxleyi (strain 1516) responds to N and P limitation. We observed modest changes in much of the proteome despite large physiological changes (e.g. cellular biomass, C, N and P) associated with nutrient limitation of growth rate. Acclimation to nutrient limitation did however involve significant increases in the abundance of transporters for ammonium and nitrate under N limitation and for phosphate under P limitation. More notable were large increases in proteins involved in the acquisition of organic forms of N and P, including urea and amino acid/polyamine transporters and numerous C‐N hydrolases under N limitation and a large upregulation of alkaline phosphatase under P limitation. This highly targeted reorganization of the proteome towards scavenging organic forms of macronutrients gives unique insight into the molecular mechanisms that underpin how E . huxleyi has found its niche to bloom in surface waters depleted of inorganic nutrients.

Highlights

Marine phytoplankton require the essential macronutrients C, N and P for biosynthesis, which on average are required in the molar ratio described by Redfield of C106 : N16 : P1 (Moore et al, 2013)
As well as inorganic nutrients, some phytoplankton utilize dissolved organic N (DON), which consists of compounds such as urea, amino acids, amides, methylamines and purines, and dissolved organic P (DOP), which exists in a many forms of P-esters or phosphonates
Cellular biovolume was highly correlated with cellular particulate organic carbon (POC) content (r = 0.92; P < 0.0001) and particulate inorganic carbon (PIC) content (r = 0.89; P < 0.0001), less so with cellular N content (r = 0. 61; P = 0.045), but not with cellular phosphorus (r = −0.36; P = ns)

Summary

Limitation of marine primary production by the availability of nitrogen or phosphorus is common. To understand physiological mechanisms that allow such blooms, we examined how the proteome of E. huxleyi (strain 1516) responds to N and P limitation. More notable were large increases in proteins involved in the acquisition of organic forms of N and P, including urea and amino acid/polyamine transporters and numerous C-N hydrolases under N limitation and a large upregulation of alkaline phosphatase under P limitation. This highly targeted reorganization of the proteome towards scavenging organic forms of macronutrients gives unique insight into the molecular mechanisms that underpin how E. huxleyi has found its niche to bloom in surface waters depleted of inorganic nutrients

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Experimental procedures