The requirement for external carbonic anhydrase in diatoms is influenced by the supply and demand for dissolved inorganic carbon

Keys, M, Hopkinson, B, Highfield, A, Chrachri, A, Brownlee, C and Wheeler, G 2023 The requirement for external carbonic anhydrase in diatoms is influenced by the supply and demand for dissolved inorganic carbon. Journal of Phycology. https://doi.org/10.1111/jpy.13416

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Abstract/Summary

Photosynthesis by marine diatoms contributes significantly to the global carbon cycle. Due to the low concentration of CO2 in seawater, many diatoms use extracellular carbonic anhydrase (eCA) to enhance the supply of CO2 to the cell surface. While much research has investigated how the requirement for eCA is influenced by changes in CO2 availability, little is known about how eCA contributes to CO2 supply following changes in the demand for carbon. We therefore examined how changes in photosynthetic rate influence the requirement for eCA in three centric diatoms. Modeling of cell surface carbonate chemistry indicated that diffusive CO2 supply to the cell surface was greatly reduced in large diatoms at higher photosynthetic rates. Laboratory experiments demonstrated a trend of an increasing requirement for eCA with increasing photosynthetic rate that was most pronounced in the larger species, supporting the findings of the cellular modeling. Microelectrode measurements of cell surface pH and O2 demonstrated that individual cells exhibited an increased contribution of eCA to photosynthesis at higher irradiances. Our data demonstrate that changes in carbon demand strongly influence the requirement for eCA in diatoms. Cell size and photosynthetic rate will therefore be key determinants of the mode of dissolved inorganic carbon uptake.

Item Type:	Publication - Article
Additional Keywords:	bicarbonate uptake(HCO3−), CO2 diffusion, diatom, diffusive boundary layer (DBL), dissolved inorganic carbon (DIC), external carbonic anhydrase (eCA)
Subjects:	Botany Chemistry Marine Sciences
Divisions:	Marine Biological Association of the UK > Marine Microbiome
Depositing User:	Ms Kristina Hixon
Date made live:	08 Jan 2024 12:20
Last Modified:	09 Feb 2024 17:08
URI:	https://plymsea.ac.uk/id/eprint/10095

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