title: A stable-isotope mass spectrometry-based metabolic footprinting approach to analyze exudates from phytoplankton.
abstract: Phytoplankton exudates play an important role in pelagic ecology and biogeochemical cycles of elements. Exuded compounds fuel the microbial food web and often encompass bioactive secondary metabolites like sex pheromones, allelochemicals, antibiotics, or feeding attractants that mediate biological interactions. Despite this importance, little is known about the bioactive compounds present in phytoplankton exudates. We report a stable-isotope metabolic footprinting method to characterise exudates from aquatic autotrophs. Exudates from (13)C-enriched alga were concentrated by solid phase extraction and analysed by high-resolution Fourier transform ion cyclotron resonance mass spectrometry. We used the harmful algal bloom forming dinoflagellate Alexandrium tamarense to prove the method. An algorithm was developed to automatically pinpoint just those metabolites with highly (13)C-enriched isotope signatures, allowing us to discover algal exudates from the complex seawater background. The stable-isotope pattern (SIP) of the detected metabolites then allowed for more accurate assignment to an empirical formula, a critical first step in their identification. This automated workflow provides an effective way to explore the chemical nature of the solutes exuded from phytoplankton cells and will facilitate the discovery of novel dissolved bioactive compounds.
authors.affiliation: School of Biosciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK. m.viant@bham.ac.uk.
authors.forename: Ralf J M
authors.initials: RJ
authors.lastname: Weber
authors.forename: Erik
authors.initials: E
authors.lastname: Selander
authors.forename: Ulf
authors.initials: U
authors.lastname: Sommer
authors.forename: Mark R
authors.initials: MR
authors.lastname: Viant
mesh_terms: D002247:Carbon Isotopes / Q000737:chemistry*; D002478:Cells, Cultured; D004141:Dinoflagellida / Q000737:chemistry / Q000378:metabolism; D005583:Fourier Analysis; D057097:Harmful Algal Bloom; D007553:Isotope Labeling / Q000379:methods; D013058:Mass Spectrometry / Q000379:methods; D010839:Phytoplankton / Q000737:chemistry* / Q000378:metabolism*; D012623:Seawater
chemical_list: D002247:Carbon Isotopes