A team of biologists from the United States, Canada, Panama and Taiwan has isolated a new species of cyanobacteria from a tropical hornwort plant found in Panama. The discovery, reported in a paper in the Current Biology, opens a new window to further illuminate the dawn of oxygenic photosynthesis.
The newly-discovered cyanobacteria species belongs to the Gloeobacteria group, which is extremely rare.
Scientifically named Anthocerotibacter panamensis, it diverged from the closest known Gloeobacter species over 1.4 billion years ago.
“Prior to this discovery, only two species of Gloeobacteria had been isolated,” said Dr. Fay-Wei Li, a researcher in the Boyce Thompson Institute and the Plant Biology Section at Cornell University.
“There is also a third group of uncultured species from the Arctic and Antarctic regions, but no one knows how many species are in that group.”
Gloeobacteria diverged from the more commonly studied Phycobacteria about 2 billion years ago.
The two groups have many differences, and Anthocerotibacter panamensis shares some traits with each.
Similar to other Gloeobacteria, the new species lacks thylakoids — the membrane-bound compartments that are the site of the light-dependent reactions of photosynthesis in Phycobacteria and plants.
“Now we can be pretty sure that the thylakoid evolved in Phycobacteria,” Dr. Li said.
On the other hand, Anthocerotibacter panamensis makes carotenoids — a group of compounds that help protect an organism from sun damage — in a fashion similar to Phycobacteria and plants, but different from other Gloeobacteria.
“These results suggest that this particular carotenoid biosynthesis pathway evolved in the ancestor of all cyanobacteria, and then was lost in some Gloeobacteria,” Dr. Li said.
“One of the more interesting findings is that Anthocerotibacter panamensis has very few genes that encode the proteins that perform light-dependent reactions.”
“The new species could still perform photosynthesis, but very slowly, which could be of interest to synthetic biologists.”
“If you want to build a complete set of photosynthetic machinery with the fewest necessary components, then this species could inform how to do that.”
“Anthocerotibacter panamensis has a minimal set of photosystem subunits, but it still functions.”
Nasim Rahmatpour et al. A novel thylakoid-less isolate fills a billion-year gap in the evolution of Cyanobacteria. Current Biology, published online May 13, 2021; doi: 10.1016/j.cub.2021.04.042