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World - Study Unravels Pathway Used by Diatoms for Removing CO2 from Atmosphere

Diatoms are small unicellular plants that do not grow bigger than half a millimeter. These plants populate the surface water of the world’s oceans where penetration of sunlight is abundant.

In spite of having a modest size, the diatoms are considered as one of the strongest resources in the world for carbon dioxide (CO2) removal from the air. Now, they eliminate, or “fix,” 10 to 20 billion metric tons of CO2 annually with the help of photosynthesis.

However, there is not much knowledge gained regarding which biological mechanisms are used by the diatoms, and if these processes may turn out to be less effective with increasing temperatures, ocean acidity, and especially CO2 concentrations.

A new study published in the journal Frontiers in Plant Science has demonstrated that diatoms largely make use of one pathway to concentrate CO2 in the proximity of carbon fixing enzyme and that they continuously do this even when the CO2 concentrations are quite high.

To concentrate CO2 obtained from the air, or water, and converting it into organic carbon, the plant kingdom has developed an extensive range of mechanisms. Thus, plants tend to convert CO2 into glucose and other carbohydrates, which are eventually used as energy storage and building blocks.

However, such mechanisms have different weaknesses and strengths. A slightly ironic fact is that the only carbon-fixing enzyme, called RuBisCO, is dreadfully inefficient at fixing CO2 and thus plants must keep CO2 levels high when this enzyme exists.

To gain better insights into which mechanisms are utilized by the diatoms to concentrate CO2, Biswas together with her collaborators, Drs Chris Bowler and Juan Jose Pierella Karluich from the Institut de Biologie de I’Ecole Normale Supérieure, Paris, France, extracted a data set from the Tara Oceans research expedition.

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