title: Use of plankton-derived vitamin B1 precursors, especially thiazole-related precursor, by key marine picoeukaryotic phytoplankton.
abstract: Several cosmopolitan marine picoeukaryotic phytoplankton are B1 auxotrophs requiring exogenous vitamin B1 or precursor to survive. From genomic evidence, representatives of picoeukaryotic phytoplankton (Ostreococcus and Micromonas spp.) were predicted to use known thiazole and pyrimidine B1 precursors to meet their B1 demands, however, recent culture-based experiments could not confirm this assumption. We hypothesized these phytoplankton strains could grow on precursors alone, but required a thiazole-related precursor other the well-known and extensively tested 4-methyl-5-thiazoleethanol. This hypothesis was tested using bioassays and co-cultures of picoeukaryotic phytoplankton and bacteria. We found that specific B1-synthesizing proteobacteria and phytoplankton are sources of a yet-to-be chemically identified thiazole-related precursor(s) that, along with pyrimidine B1 precursor 4-amino-5-hydroxymethyl-2-methylpyrimidine, can support growth of Ostreococcus spp. (also Micromonas spp.) without B1. We additionally found that the B1-synthesizing plankton do not require contact with picoeukaryotic phytoplankton cells to produce thiazole-related precursor(s). Experiments with wild-type and genetically engineered Ostreococcus lines revealed that the thiazole kinase, ThiM, is required for growth on precursors, and that thiazole-related precursor(s) accumulate to appreciable levels in the euphotic ocean. Overall, our results point to thiazole-related B1 precursors as important micronutrients promoting the survival of abundant phytoplankton influencing surface ocean production and biogeochemical cycling.
authors.affiliation: Marine Biology Research Division, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA, USA.
authors.forename: Ryan W
authors.initials: RW
authors.lastname: Paerl
authors.affiliation: Sorbonne Universités, Université Pierre and Marie Curie (Paris 06), UMR 7621, Laboratoire d'Océanographie Microbienne, Observatoire Océanologique, Banyuls-sur-Mer, France.
authors.forename: Francois-Yves
authors.initials: FY
authors.lastname: Bouget
authors.affiliation: Sorbonne Universités, Université Pierre and Marie Curie (Paris 06), UMR 7621, Laboratoire d'Océanographie Microbienne, Observatoire Océanologique, Banyuls-sur-Mer, France.
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Lozano
authors.affiliation: Sorbonne Universités, Université Pierre and Marie Curie (Paris 06), UMR 7621, Laboratoire d'Océanographie Microbienne, Observatoire Océanologique, Banyuls-sur-Mer, France.
authors.forename: Valérie
authors.initials: V
authors.lastname: Vergé
authors.affiliation: Sorbonne Universités, Université Pierre and Marie Curie (Paris 06), UMR 7621, Laboratoire d'Océanographie Microbienne, Observatoire Océanologique, Banyuls-sur-Mer, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Schatt
authors.affiliation: Marine Biology Research Division, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA, USA.
authors.forename: Eric E
authors.initials: EE
authors.lastname: Allen
authors.affiliation: Marine Biology Research Division, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA, USA.
authors.forename: Brian
authors.initials: B
authors.lastname: Palenik
authors.affiliation: Marine Biology Research Division, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA, USA.
authors.forename: Farooq
authors.initials: F
authors.lastname: Azam
mesh_terms: D000460:Chlorophyta / Q000235:genetics; D056890:Eukaryota / Q000378:metabolism*; D010933:Plankton / Q000145:classification* / Q000378:metabolism; D011743:Pyrimidines; D013831:Thiamine / Q000737:chemistry* / Q000378:metabolism*; D013844:Thiazoles / Q000378:metabolism*
chemical_list: C101901:4-amino-5-hydroxymethyl-2-methylpyrimidine; D011743:Pyrimidines; D013844:Thiazoles; D013831:Thiamine