Factors Influencing the Diversity of Iron Uptake Systems in Aquatic Microorganisms.

Desai, Dhwani K., Desai, Falguni D. and LaRoche, Julie (2012) Factors Influencing the Diversity of Iron Uptake Systems in Aquatic Microorganisms. Open Access Frontiers in Microbiology, 3 (362). DOI 10.3389/fmicb.2012.00362.

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Supplementary data:

Abstract

Iron (Fe) is an essential micronutrient for many processes in all living cells. Dissolved Fe (dFe) concentrations in the ocean are of the order of a few nM, and Fe is often a factor limiting primary production. Bioavailability of Fe in aquatic environments is believed to be primarily controlled through chelation by Fe-binding ligands. Marine microbes have evolved different mechanisms to cope with the scarcity of bioavailable dFe. Gradients in dFe concentrations and diversity of the Fe-ligand pool from coastal to open ocean waters have presumably imposed selection pressures that should be reflected in the genomes of microbial communities inhabiting the pelagic realm. We applied a hidden Markov model (HMM)-based search for proteins related to cellular iron metabolism, and in particular those involved in Fe uptake mechanisms in 164 microbial genomes belonging to diverse taxa and occupying different aquatic niches. A multivariate statistical approach demonstrated that in phototrophic organisms, there is a clear influence of the ecological niche on the diversity of Fe uptake systems. Extending the analyses to the metagenome database from the Global Ocean Sampling expedition, we demonstrated that the Fe uptake and homeostasis mechanisms differed significantly across marine niches defined by temperatures and dFe concentrations, and that this difference was linked to the distribution of microbial taxa in these niches. Using the dN/dS ratios (which signify the rate of non-synonymous mutations) of the nucleotide sequences, we identified that genes encoding for TonB, Ferritin, Ferric reductase, IdiA, ZupT, and Fe(2+) transport proteins FeoA and FeoB were evolving at a faster rate (positive selection pressure) while genes encoding ferrisiderophore, heme and Vitamin B12 uptake systems, siderophore biosynthesis, and IsiA and IsiB were under purifying selection pressure (evolving slowly).

Document Type: Article
Keywords: marine microbes, eukaryotic phytoplankton, Fe limitation, Fe- binding ligands, multivariate statistics, metagenomes, dN/dS ratio, aquatic niches
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BI Biological Oceanography
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: 10.3389/fmicb.2012.00362
ISSN: 1664-302X
Projects: SOPRAN
Date Deposited: 23 Nov 2012 12:44
Last Modified: 08 Jan 2016 11:32
URI: http://oceanrep.geomar.de/id/eprint/19280

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