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Published on: January 7, 2019
Sustained net CO2 evolution during photosynthesis by marine microorganisms
D Tchernov1, M Hassidim, B Luz
1Department of Plant Sciences, Hebrew University of Jerusalem, Israel.
Current Biology : CB
|November 22, 1997
Summary
Marine microbes can release carbon dioxide (CO2) during photosynthesis, challenging the view of them solely as CO2 sinks. This surprising CO2 evolution from bicarbonate uptake has implications for marine carbon cycling and cellular pH regulation.
Area of Science:
- Marine microbiology
- Photosynthesis
- Biogeochemical cycles
Background:
- Aquatic photosynthetic microorganisms utilize inorganic-carbon-concentrating mechanisms to enhance CO2 availability for carboxylating enzymes.
- Cyanobacteria employ energy-dependent inorganic carbon influx and intracellular accumulation, primarily as bicarbonate (HCO3-), for CO2 concentration.
Purpose of the Study:
- To investigate inorganic carbon fluxes in marine photosynthetic microorganisms.
- To determine if these organisms can act as a source of CO2 during photosynthesis.
Main Methods:
- Measurement of inorganic carbon fluxes in marine microorganisms, including Synechococcus sp. WH7803.
- Stable isotope measurements of oxygen exchange to trace CO2 origin.
- Assessment of external CO2 concentrations and response to carbonic anhydrase addition.
Main Results:
- Several marine photosynthetic microorganisms, including Synechococcus sp. WH7803, were observed to evolve CO2 during photosynthesis.
- CO2 evolution rates increased with light intensity and were significantly higher than predicted by chemical equilibrium.
- Stable isotope measurements confirmed that evolved CO2 originated from intracellularly converted bicarbonate (HCO3-) in a light-dependent process.
Conclusions:
- Photosynthetic microorganisms can exhibit net, sustained CO2 evolution.
- This finding has implications for cellular energy balance and pH regulation.
- The study impacts understanding of marine carbon cycling and stable carbon isotope fractionation.
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