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- Title
Characterization of a CO2-Concentrating Mechanism with Low Sodium Dependency in the Centric Diatom Chaetoceros gracilis.
- Authors
Tsuji, Yoshinori; Kusi-Appiah, George; Kozai, Noriko; Fukuda, Yuri; Yamano, Takashi; Fukuzawa, Hideya
- Abstract
Microalgae induce a CO2-concentrating mechanism (CCM) to overcome CO2-limiting stress in aquatic environments by coordinating inorganic carbon (Ci) transporters and carbonic anhydrases (CAs). Two mechanisms have been suggested to facilitate Ci uptake from aqueous media: Na+-dependent HCO3− uptake by solute carrier (SLC) family transporters and accelerated dehydration of HCO3− to CO2 by external CA in model diatoms. However, studies on ecologically and industrially important diatoms including Chaetoceros gracilis, a common food source in aquacultures, are still limited. Here, we characterized the CCM of C. gracilis using inhibitors and growth dependency on Na+ and CO2. Addition of a membrane-impermeable SLC inhibitor, 4,4′-diisothiocyano-2,2′-stilbenedisulfonic acid (DIDS), or the transient removal of Na+ from the culture medium did not impair photosynthetic affinity for Ci in CO2-limiting stress conditions, but addition of a membrane-impermeable CA inhibitor, acetazolamide, decreased Ci affinity to one-third of control cultures. In culture medium containing 0.23 mM Na+C. gracilis grew photoautotrophically by aeration with air containing 5% CO2, but not with the air containing 0.04% CO2. These results suggested that C. gracilis utilizes external CAs in its CCM to elevate photosynthetic affinity for Ci rather than plasma-membrane SLC family transporters. In addition, it is possible that low level of Na+ may support the CCM in processes other than Ci-uptake at the plasma membrane specifically in CO2-limiting conditions. Our findings provide insights into the diversity of CCMs among diatoms as well as basic information to optimize culture conditions for industrial applications.
- Publication
Marine Biotechnology, 2021, Vol 23, Issue 3, p456
- ISSN
1436-2228
- Publication type
Article
- DOI
10.1007/s10126-021-10037-4