Heterologous expression in E. coli reveals that bicarbonate transporter BicA2 mediates carbon uptake in marine Prochlorococcus spp.

BicA2 functions as a Na+-dependent bicarbonate transporter in Prochlorococcus, revealing a key component of its carbon-concentrating mechanism with variable activity.

• Why it matters: Understanding how Prochlorococcus acquires inorganic carbon is crucial because it is the most abundant photosynthetic organism on Earth, significantly impacting global carbon cycles. The absence of canonical CO2 pumps in this genus has left gaps in knowledge about its CCM.
• What they did: The study expressed BicA2 from two Prochlorococcus strains in E. coli, demonstrating that one mediates bicarbonate uptake while the other requires a single amino acid change to become active, highlighting its adaptive potential.
• The result: This discovery confirms BicA2 as a low-affinity bicarbonate transporter with variable flux, advancing our understanding of Prochlorococcus’s carbon acquisition and its evolutionary flexibility, with implications for biogeochemical modeling.