A CO2-guzzling bacteria could help us improve carbon capture plants

In a bid to solve our climate woes, a team of researchers from Simon Fraser University is working with the Canadian Light Source (CLS) at the University of Saskatchewan to investigate the role carbon dioxide (CO₂) plays in cyanobacteria, which are photosynthetic organisms that are found in water, according to a press release.

The researchers believe that by better understanding how organisms perceive and react to CO₂, they can improve both human and environmental health as well as develop new carbon capture methods.

This means bacteria may soon join humanity’s toolbelt in lowering the amount of carbon dioxide in the atmosphere and fighting climate change.

Cyanobacteria explained

In case you haven't heard of them before, you should know that there is much to admire about cyanobacteria. These tiny, photosynthetic organisms, which are both aquatic and photosynthetic, fix CO₂ twice as efficiently as plants. They are unicellular and tiny, though they can sometimes form colonies large enough to see. They grow extremely fast, doubling in number every three hours.

Moreover, they are the oldest known fossils, dating back more than 3.5 billion years, according to Berkeley University, which is why it could come as a surprise to learn that cyanobacteria still exist. In fact, they are one of the largest and most significant groups of bacteria on Earth. Researchers believe that these organisms could even be used to produce high-performance biofuels or chemicals in carbon-fueled bioreactors.

And now, the new study suggests that by combining the systems within these organisms with industrial processes we may be able to cut CO₂ emissions.

Striking a balance

In their study, which has been published in the journal Nature Chemical Biology, the researchers were able to visualize intricate molecular structures and study how CO₂ binds to a bacterial protein.

The researchers explained that, as CO₂ is electrophilic (the molecule or ion that is electron deficient), one way it can influence protein biochemistry is through carboxylation of lysine amine groups. However, the resulting CO₂-carboxylated lysines spontaneously break down, emitting CO₂, which makes research difficult.

The researchers found a strategy for stably mimicking CO₂-carboxylated lysine residues in proteins and used the technology to create a quantitative method for identifying CO₂-carboxylated lysines in proteins and to investigate the lysine "carboxylome" of the CO₂-responsive cyanobacterium Synechocystis sp.

The researchers discovered one CO₂-carboxylated lysine within the effector binding site of the metabolic signaling protein PII. CO_2-carboxylation of this lysine significantly reduces its affinity for its regulatory effector ligand ATP, revealing a negative molecular control mechanism mediated by CO₂.

Cyanobacteria "are able to capture [CO2] from the atmosphere, fix it directly, and add it to simple organic molecules” said Dustin King, a postdoctoral researcher in the university’s Department of Chemistry. “Understanding how cyanobacteria regulate CO₂ fixation may give us an avenue for developing improved CO₂ capture technologies.” 

Abstract:

Carbon dioxide is an omnipresent gas that drives adaptive responses within organisms from all domains of life. The molecular mechanisms by which proteins serve as sensors of CO2 are, accordingly, of great interest. Because CO2 is electrophilic, one way it can modulate protein biochemistry is by carboxylation of the amine group of lysine residues. However, the resulting CO2-carboxylated lysines spontaneously decompose, giving off CO2, which makes studying this modification difficult. Here we describe a method to stably mimic CO2-carboxylated lysine residues in proteins. We leverage this method to develop a quantitative approach to identify CO2-carboxylated lysines of proteins and explore the lysine ‘carboxylome’ of the CO2-responsive cyanobacterium Synechocystis sp. We uncover one CO2-carboxylated lysine within the effector binding pocket of the metabolic signaling protein PII. CO2-carboxylatation of this lysine markedly lowers the affinity of PII for its regulatory effector ligand ATP, illuminating a negative molecular control mechanism mediated by CO2.