Cyanobacteria are one of the unsung heroes of life on Earth. They first evolved to photosynthesize about 2.4 billion years ago, pumping tons of oxygen into the atmosphere – a period known as the Great Oxygenation Event – which enabled the evolution of multicellular life forms.
Led by BTI faculty member Fay-Wei Li, the researchers discovered a new species of cyanobacteria, Anthocerotibacter panamensis, which could help shed light on how photosynthesis evolved to create the world as we know it. The work was published in Current biology May 13.
“We never intended to find a new species,” Li said. “It was a total accident.”
His lab was working on a project to isolate cyanobacteria from crow plants and noticed something bizarre in a sample from a tropical forest in Panama. The researchers sequenced the cyanobacteria’s DNA and found that it belonged to a group called Gloeobacteria, which is extremely rare.
“Prior to this discovery, only two species of Gloeobacteria had been isolated,” Li said. “There is also a third group of uncultivated species from the Arctic and Antarctic regions, but no one knows how many species there are in this. group.”
Gloeobacteria diverged from the most studied phycobacteria about 2 billion years ago. The two groups show many differences and A. panamensis shares some traits with each.
Similar to other Gloeobacteria, the new species lacks thylakoids – the membrane-bound compartments that are the site of light-dependent photosynthetic reactions in phycobacteria and plants.
“Now we can be pretty sure that the thylakoid evolved into phycobacteria,” Li said.
On the other hand, A. panamensis makes carotenoids – a group of compounds that help protect an organism from sun damage – in a way similar to phycobacteria and plants, but different from other gloeobacteria.
“These results suggest that this particular pathway of carotenoid biosynthesis evolved into the ancestor of all cyanobacteria and then was lost in some Gloeobacteria,” Li said.
Li said that one of the most interesting findings is that A. panamensis has very few genes encoding proteins that perform light-dependent reactions. The researchers found that the new species could still photosynthesize, but very slowly, which may be of interest to synthetic biologists.
“If you want to build a complete set of photosynthetic machines with the fewest components needed, then this species could show you how to do it,” Li said. “Anthocerotibacter has a minimal set of photosystem subunits, but it still works. . “
Source of the story:
Material provided by Boyce Thompson Institute. Original written by Aaron J. Bouchie. Note: Content can be changed for style and length.