Researchers study how certain bacteria perform photosynthesis

By studying the way two bacteria perform the difficult chemistry of photosynthesis, a team led by Imperial College London researchers have discovered the trade-offs they make when using lower-energy light.

This could inform plant genetic engineering that aims to make crop and biomass production more efficient.

Plants, algae and cyanobacteria (blue-green algae) perform photosynthesis to convert light and CO₂ into sugars and oxygen. An enzyme called photosystem II performs the first step of this process, using light to extract electrons from water and feed them into the photosynthetic machinery.

Most organisms perform photosynthesis using visible light, which they collect thanks to a pigment called chlorophyll-a. The energy contained in visible light has been considered for a long time the minimum energy required to do the hard chemistry of extracting electrons from water.

However, there are some cyanobacteria that perform photosynthesis using lower-energy far-red light instead of visible light. Giving plants and algae the ability to use far-red light could make crop and biomass production more efficient, since far-red light is less energy intensive and is plentiful.

The ability to use both visible and far-red light in different conditions would also be a desirable property for crop plants and algae, but the researchers needed to understand if there were any trade-offs or compromises in systems that can do this.

The team studied cyanobacteria that perform photosynthesis using far-red light instead of visible light. Acaryochloris marina lives beneath a green sea-squirt, shaded from visible light but exposed to stable far-red light, that it collects using the pigment chlorophyll-d instead of chlorophyll-a.

Other recently discovered cyanobacteria can do photosynthesis using chlorophyll-a when visible light is present and then switch to using the pigment chlorophyll-f, which also absorbs far-red light, when shaded from visible light.

In 2018, researchers led by a team at Imperial discovered that in one of these cyanobacteria, Chroococcidiopsis thermalis, photosystem II can do the hard chemistry by solely using the lower energy provided by far-red light.

Now, in a study published in eLife, researchers led by the same team at Imperial have shown that the photosystem II of cyanobacteria using the pigment chlorophyll-f is less efficient at collecting and using far-red light than the photosystem II of those using chlorophyll-d, but that it is more protected from the damaging side-effects of too much light.

According to lead researcher Professor Bill Rutherford, from the department of life sciences at Imperial, engineering crop plants or algae that could use far-red photosynthesis may help boost food and biomass production.

"Our study is an important first step in understanding the trade-offs between efficiency and resilience in systems that can use far-red light. These insights could help researchers determine which features would be beneficial, and under what conditions,” he said.

PHOTO:  By studying the way two bacteria perform the difficult chemistry of photosynthesis, a team led by Imperial College London researchers have discovered the trade-offs they make when using lower-energy light. (Image: Imperial College London)

Learn about biocontrol and the science of biomes at New AG International's event 13-14 December, Biocontrol & Biomes, in Madrid, Spain, here.

RETURN to home page and read our latest New AG International issue, here.