title: Phosphate Limitation Triggers the Dissolution of Precipitated Iron by the Marine BacteriumPseudovibriosp. FO-BEG1.
abstract: Phosphorus is an essential nutrient for all living organisms. In bacteria, the preferential phosphorus source is phosphate, which is often a limiting macronutrient in many areas of the ocean. The geochemical cycle of phosphorus is strongly interconnected with the cycles of other elements and especially iron, because phosphate tends to adsorb onto iron minerals, such as iron oxide formed in oxic marine environments. Although the response to either iron or phosphate limitation has been investigated in several bacterial species, the metabolic interplay between these two nutrients has rarely been considered. In this study we evaluated the impact of phosphate limitation on the iron metabolism of the marine bacteriumPseudovibriosp. FO-BEG1. We observed that phosphate limitation led to an initial decrease of soluble iron in the culture up to three times higher than under phosphate surplus conditions. Similarly, a decrease in soluble cobalt was more pronounced under phosphate limitation. These data point toward physiological changes induced by phosphate limitation that affect either the cellular surface and therefore the metal adsorption onto it or the cellular metal uptake. We discovered that under phosphate limitation strain FO-BEG1, as well as selected strains of theRoseobacterclade, secreted iron-chelating molecules. This leads to the hypothesis that these bacteria might release such molecules to dissolve iron minerals, such as iron-oxyhydroxide, in order to access the adsorbed phosphate. As the adsorption of phosphate onto iron minerals can significantly decrease phosphate concentrations in the environment, the observed release of iron-chelators might represent an as yet unrecognized link between the biogeochemical cycle of phosphorus and iron, and it suggests another biological function of iron-chelating molecules in addition to metal-scavenging.
authors.affiliation: Max Planck Institute for Marine Microbiology, Bremen, Germany.
authors.forename: Stefano
authors.initials: S
authors.lastname: Romano
authors.affiliation: Max Planck Institute for Marine Microbiology, Bremen, Germany.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Bondarev
authors.affiliation: Marum Center for Marine Environmental Sciences, Bremen, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Kölling
authors.affiliation: ICBM-MPI Bridging Group for Marine Geochemistry, Institute for Chemistry and Biology of the Marine Environment, Carl von Ossietzky University, Oldenburg, Germany.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Dittmar
authors.affiliation: Biological Oceanography, Leibniz Institut für Ostseeforschung, Warnemünde, Germany.
authors.forename: Heide N
authors.initials: HN
authors.lastname: Schulz-Vogt
keywords: Pseudovibrio; Roseobacter; bacterial physiology; chelators; mass spectrometry; metabolomics; phosphate limitation; siderophores