title: Chemical microenvironments and single-cell carbon and nitrogen uptake in field-collected colonies of Trichodesmium under different pCO2.
abstract: Gradients of oxygen (O2) and pH, as well as small-scale fluxes of carbon (C), nitrogen (N) and O2were investigated under different partial pressures of carbon dioxide (pCO2) in field-collected colonies of the marine dinitrogen (N2)-fixing cyanobacterium Trichodesmium. Microsensor measurements indicated that cells within colonies experienced large fluctuations in O2, pH and CO2concentrations over a day-night cycle. O2concentrations varied with light intensity and time of day, yet colonies exposed to light were supersaturated with O2(up to ~200%) throughout the light period and anoxia was not detected. Alternating between light and dark conditions caused a variation in pH levels by on average 0.5 units (equivalent to 15 nmol l-1proton concentration). Single-cell analyses of C and N assimilation using secondary ion mass spectrometry (SIMS; large geometry SIMS and nanoscale SIMS) revealed high variability in metabolic activity of single cells and trichomes of Trichodesmium, and indicated transfer of C and N to colony-associated non-photosynthetic bacteria. Neither O2fluxes nor C fixation by Trichodesmium were significantly influenced by short-term incubations under different pCO2levels, whereas N2fixation increased with increasing pCO2. The large range of metabolic rates observed at the single-cell level may reflect a response by colony-forming microbial populations to highly variable microenvironments.
authors.affiliation: Department of Marine Sciences, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Meri J
authors.initials: MJ
authors.lastname: Eichner
authors.affiliation: Department of Ecology, Environment and Plant Sciences, University of Stockholm, Stockholm, Sweden.
authors.forename: Isabell
authors.initials: I
authors.lastname: Klawonn
authors.affiliation: Daniel K. Inouye Center for Microbial Oceanography: Research and Education, University of Hawaii, Honolulu, HI, USA.
authors.forename: Samuel T
authors.initials: ST
authors.lastname: Wilson
authors.affiliation: Department of Biogeochemistry, Max Planck Institute for Marine Microbiology, Bremen, Germany.
authors.forename: Sten
authors.initials: S
authors.lastname: Littmann
authors.affiliation: Department of Geosciences, Swedish Museum of Natural History, Stockholm, Sweden.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Whitehouse
authors.affiliation: Daniel K. Inouye Center for Microbial Oceanography: Research and Education, University of Hawaii, Honolulu, HI, USA.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Church
authors.affiliation: Department of Biogeochemistry, Max Planck Institute for Marine Microbiology, Bremen, Germany.
authors.forename: Marcel Mm
authors.initials: MM
authors.lastname: Kuypers
authors.affiliation: Daniel K. Inouye Center for Microbial Oceanography: Research and Education, University of Hawaii, Honolulu, HI, USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Karl
authors.affiliation: Department of Marine Sciences, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Helle
authors.initials: H
authors.lastname: Ploug
mesh_terms: D002244:Carbon / Q000378:metabolism*; D057486:Carbon Cycle / Q000502:physiology; D002245:Carbon Dioxide / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D008027:Light; D009584:Nitrogen / Q000378:metabolism*; D009586:Nitrogen Fixation / Q000502:physiology; D010100:Oxygen / Q000378:metabolism; D010788:Photosynthesis; D000072359:Trichodesmium / Q000378:metabolism*
chemical_list: D002245:Carbon Dioxide; D002244:Carbon; D009584:Nitrogen; D010100:Oxygen