Photolysis of iron-siderophore chelates promotes bacterial-algal mutualism

被引:423
作者
Amin, Shady A. [1 ]
Green, David H. [2 ]
Hart, Mark C. [2 ]
Kuepper, Frithjof C. [2 ]
Sunda, William G. [3 ]
Carrano, Carl J. [1 ]
机构
[1] San Diego State Univ, Dept Chem & Biochem, San Diego, CA 92182 USA
[2] Dunstaffnage Marine Res Lab, Scottish Assoc Marine Sci, Oban PA37 1QA, Argyll, Scotland
[3] NOAA, Beaufort Lab, Beaufort, NC 28516 USA
基金
英国自然环境研究理事会;
关键词
algal blooms; iron acquisition; vibrioferrin; Marinobacter; photochemistry; MARINE-BACTERIA; PHYTOPLANKTON; IRON(III); CHEMISTRY; PACIFIC; LIGANDS; ACQUISITION; TRANSPORT; RELEASE; BINDING;
D O I
10.1073/pnas.0905512106
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
Marine microalgae support world fisheries production and influence climate through various mechanisms. They are also responsible for harmful blooms that adversely impact coastal ecosystems and economies. Optimal growth and survival of many bloom-forming microalgae, including climatically important dinoflagellates and coccolithophores, requires the close association of specific bacterial species, but the reasons for these associations are unknown. Here, we report that several clades of Marinobacter ubiquitously found in close association with dinoflagellates and coccolithophores produce an unusual lower-affinity dicitrate siderophore, vibrioferrin (VF). Fe-VF chelates undergo photolysis at rates that are 10-20 times higher than siderophores produced by free-living marine bacteria, and unlike the latter, the VF photoproduct has no measurable affinity for iron. While both an algal-associated bacterium and a representative dinoflagellate partner, Scrippsiella trochoidea, used iron from Fe-VF chelates in the dark, in situ photolysis of the chelates in the presence of attenuated sunlight increased bacterial iron uptake by 70% and algal uptake by >20-fold. These results suggest that the bacteria promote algal assimilation of iron by facilitating photochemical redox cycling of this critical nutrient. Also, binary culture experiments and genomic evidence suggest that the algal cells release organic molecules that are used by the bacteria for growth. Such mutualistic sharing of iron and fixed carbon has important implications toward our understanding of the close beneficial interactions between marine bacteria and phytoplankton, and the effect of these interactions on algal blooms and climate.
引用
收藏
页码:17071 / 17076
页数:6
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