title: Diversity of CO2-concentrating mechanisms and responses to CO2 concentration in marine and freshwater diatoms.
abstract: The presence of CO2-concentrating mechanisms (CCMs) is believed to be one of the characteristics that allows diatoms to thrive in many environments and to be major contributors to global productivity. Here, the type of CCM and the responses to variable CO2 concentration were studied in marine and freshwater diatoms. At 400 ppm, there was a large diversity in physiological and biochemical mechanisms among the species. While Phaeodactylum tricornutum mainly used HCO3-, Thalassiosira pseudonana mainly used CO2. Carbonic anhydrase was an important component of the CCM in all species and C4 metabolism was absent, even with T. weissflogii. For all species, at 20 000 ppm, the affinity for dissolved inorganic carbon was lower than at 400 ppm CO2 and the reliance on CO2 was higher. Despite the difference in availability of inorganic carbon in marine and fresh waters, there were only small differences in CCMs between species from the two environments, and Navicula pelliculosa behaved similarly when grown in the two environments. The results suggest that species-specific differences are great, and more important than environmental differences in determining the nature and effectiveness of the CCM in diatoms.
authors.affiliation: Aix Marseille Univ, CNRS, BIP, UMR 7281, IMM, 31 Chemin J. Aiguier, 13 402 Marseille Cedex 20, France.
authors.forename: Romain
authors.initials: R
authors.lastname: Clement
authors.affiliation: Aix Marseille Univ, CNRS, BIP, UMR 7281, IMM, 31 Chemin J. Aiguier, 13 402 Marseille Cedex 20, France.
authors.forename: Erik
authors.initials: E
authors.lastname: Jensen
authors.affiliation: Aix Marseille Univ, CNRS, BIP, UMR 7281, IMM, 31 Chemin J. Aiguier, 13 402 Marseille Cedex 20, France.
authors.forename: Laura
authors.initials: L
authors.lastname: Prioretti
authors.affiliation: Lake Ecosystems Group, Centre for Ecology & Hydrology, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster LA1 4APUK.
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Maberly
authors.affiliation: Aix Marseille Univ, CNRS, BIP, UMR 7281, IMM, 31 Chemin J. Aiguier, 13 402 Marseille Cedex 20, France.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Gontero
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D017377:Diatoms / Q000378:metabolism*; D004777:Environment; D005618:Fresh Water; D010788:Photosynthesis; D012623:Seawater; D013045:Species Specificity
chemical_list: D002245:Carbon Dioxide
keywords: Bicarbonate use; C4 photosynthesis; CCM; PEP carboxylase; PPDK; Rubisco; carbon dioxide-concentrating mechanism; carbonic anhydrase; diatoms; pH-drift; photosynthesis