Biology

Genomic mosaicism underlies the adaptation of marine Synechococcus ecotypes to distinct oceanic iron niches

Document Type

Article

Abstract

Phytoplankton are limited by iron (Fe) in ~40% of the world's oceans including high-nutrient low-chlorophyll (HNLC) regions. While low-Fe adaptation has been well-studied in large eukaryotic diatoms, less is known for small, prokaryotic marine picocyanobacteria. This study reveals key physiological and genomic differences underlying Fe adaptation in marine picocyanobacteria. HNLC ecotype CRD1 strains have greater physiological tolerance to low Fe congruent with their expanded repertoire of Fe transporter, storage and regulatory genes compared to other ecotypes. From metagenomic analysis, genes encoding ferritin, flavodoxin, Fe transporters and siderophore uptake genes were more abundant in low-Fe waters, mirroring paradigms of low-Fe adaptation in diatoms. Distinct Fe-related gene repertories of HNLC ecotypes CRD1 and CRD2 also highlight how coexisting ecotypes have evolved independent approaches to life in low-Fe habitats. Synechococcus and Prochlorococcus HNLC ecotypes likewise exhibit independent, genome-wide reductions of predicted Fe-requiring genes. HNLC ecotype CRD1 interestingly was most similar to coastal ecotype I in Fe physiology and Fe-related gene content, suggesting populations from these different biomes experience similar Fe-selective conditions. This work supports an improved perspective that phytoplankton are shaped by more nuanced Fe niches in the oceans than previously implied from mostly binary comparisons of low- versus high-Fe habitats and populations.

Publication Title

Environmental Microbiology

Publication Date

5-2020

Volume

22

Issue

5

First Page

1801

Last Page

1815

ISSN

1462-2912

DOI

10.1111/1462-2920.14893

Keywords

acclimatization, adaptation, bacterial genome, diatom; ecosystem; ecotype, genetics, metabolism, metagenomics, microbiology; mosaicism, physiology, phytoplankton, Prochlorococcus, sea, Synechococcus

Cross Post Location

Student Publications

Link to Full Text

Share

COinS