Unraveling the molecular mysteries of microalgae

Although they have existed for millions of years, microalgae – these microscopic algae found in fresh and salt water bodies around the world – have not yet revealed all their secrets. As part of his doctorate in biochemistry, Alexandre Poulhazan (Ph.D. biochemistry, 2022) set himself the objective of obtaining a complete molecular map of the microalga Chlamydomonas reinhardtii. One of the articles from his thesis, recently published in the prestigious journal Nature Communications, focused more specifically on the wall of the microalgae in question. “To understand the interactions of microalgae with contaminants, or to access what nutrients they produce, we must first unravel the mystery of the composition of their cell wall,” he explains.

“Microalgae constitute a renewable biomass that can produce biofuel or serve as an alternative nutrient source, but to be able to use them on a large scale, it is important to better understand their molecular architecture,” observes Professor of the Department of Chemistry Isabelle Marcotte, who is among co-signatories of the article with Department of Chemistry research officer and lecturer Alexandre A. Arnold, Associate Professor Dror E. Warschawski as well as American and Danish collaborators.

In her laboratory, where Alexandre Poulhazan worked, the professor is trying to better understand the interactions between microalgae, which are at the base of the food chain, and the marine contaminants that they can absorb and pass on to other species that ingest them.

A wall of glycoproteins

As part of the study, Alexandre Poulhazan used microalgae from American and French banks. “We chose to study Chlamydomonas reinhardtii because it is well known and is the equivalent of Escherichia coli (E. coli) in bacteria,” explains the researcher. There was basic data on this microalgae and it can be genetically modified to make it produce molecules of interest, such as proteins. But to extract these molecules, we must understand the composition of its wall and deconstruct it.”

Thanks to nuclear magnetic resonance (NMR) analyzes carried out mainly at UQAM as well as at the National High Magnetic Field Laboratory, located in Tallahassee, Florida, Alexandre Poulhazan was able to dismantle Chlamydomonas reinhardtii like a Lego. “I first focused on its energy reserves – the starch and sugars that it accumulates – and then tried to unravel the mysteries of its wall,” says the researcher, who has just completed a postdoctoral fellowship at the Stanford University, California.

The results reveal that the wall of Chlamydomonas reinhardtii is made up of glycoproteins, molecules composed by the bond between a protein (a set of amino acids) and a carbohydrate (sugar). “After analyzing the composition of the wall, we can create enzymes whose role will be to degrade the sugar chains and digest the wall, leaving the path clear to access what the microalgae produces,” explains Alexandre Poulhazan.

The young researcher believes that this discovery will allow those who are banking on microalgae for the future to be able to take advantage of it on a large scale if necessary.

Continuation of the study on contaminants

The interest of Alexandre Poulhazan’s thesis is that he carried out his experiments on microalgae in a hydrated medium, which NMR allows. “It was not necessary to dry out the microalgae in case this would have modified elements of its structure,” he explains. And with NMR, we were able to see that certain regions of the wall were more flexible than others, that certain parts were more in contact with water.

This was valuable information, because the secrets of the wall having been revealed, Isabelle Marcotte will now be able to put the microalgae in contact with contaminants, such as nanoplastics or metals, and observe these interactions in the laboratory. All that remains is for him to find another student as motivated, patient and tenacious as Alexandre Poulhazan, who had carried out other projects in parallel during his thesis, including that on the mysteries of worm slime. velvet.

Source : Actualités UQAM