title: Salinity-dependent diatom biosilicification implies an important role of external ionic strength.
abstract: The role of external ionic strength in diatom biosilica formation was assessed by monitoring the nanostructural changes in the biosilica of the two marine diatom species Thalassiosira punctigera and Thalassiosira weissflogii that was obtained from cultures grown at two distinct salinities. Using physicochemical methods, we found that at lower salinity the specific surface area, the fractal dimensions, and the size of mesopores present in the biosilica decreased. Diatom biosilica appears to be denser at the lower salinity that was applied. This phenomenon can be explained by assuming aggregation of smaller coalescing silica particles inside the silica deposition vesicle, which would be in line with principles in silica chemistry. Apparently, external ionic strength has an important effect on diatom biosilica formation, making it tempting to propose that uptake of silicic acid and other external ions may take place simultaneously. Uptake and transport of reactants in the proximity of the expanding silica deposition vesicle, by (macro)pinocytosis, are more likely than intracellular stabilization and transport of silica precursors at the high concentrations that are necessary for the formation of the siliceous frustule components.
authors.affiliation: Groningen Biomolecular Sciences and Biotechnology Institute, Center for Ecological and Evolutionary Studies, University of Groningen, NL-9750 AA Haren, The Netherlands. e.g.vrieling@rug.nl
authors.forename: Engel G
authors.initials: EG
authors.lastname: Vrieling
authors.forename: Qianyao
authors.initials: Q
authors.lastname: Sun
authors.forename: Mingwen
authors.initials: M
authors.lastname: Tian
authors.forename: Patricia J
authors.initials: PJ
authors.lastname: Kooyman
authors.forename: Winfried W C
authors.initials: WW
authors.lastname: Gieskes
authors.forename: Rutger A
authors.initials: RA
authors.lastname: van Santen
authors.forename: Nico A J M
authors.initials: NA
authors.lastname: Sommerdijk
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D017377:Diatoms / Q000737:chemistry / Q000254:growth & development / Q000502:physiology*; D008954:Models, Biological; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D009994:Osmolar Concentration; D012822:Silicon Dioxide / Q000737:chemistry / Q000378:metabolism*; D012965:Sodium Chloride / Q000378:metabolism*
chemical_list: D012965:Sodium Chloride; D012822:Silicon Dioxide