Applied and Environmental Science

“Ancient” Bacteria With Patchwork Genomes Are Younger Than They Seem

A few groups of modern bacteria use anoxygenic photosynthesis (photosynthesis that does not produce oxygen) as an energy source, and the scientific community has assumed that these groups are ancient lineages that evolved when the Earth’s atmosphere was largely devoid of oxygen and oxygen species.

The green, non-sulfur bacteria called Chloroflexi, commonly found in microbial mat communities, is one of these groups of ancient anoxygenic phototrophs, but the authors of this study found that anoxygenic photosynthesis in Chloroflexi only evolved after the oxygenation of the Earth’s atmosphere. Moreover, several of the genes for both photosynthesis and Chloroflexi’s unique mechanism for fixing CO2 (called the 3-hydroxyproprionate bi-cycle) were acquired from other bacteria through horizontal transfer to make a “patchwork” genome. This study highlights how both the genomes and metabolism of bacteria are much more plastic than we thought.

The original article can be found here.

Author: Albatros4825 (Own work) [CC BY-SA 4.0 (], via Wikimedia Commons
Caption: Microbial mat at Yellowstone National Park with growths of green Chloroflexus bacteria.


Citation: Shih, P. M., Ward, L. M., and Fischer, W. W. (2017). Evolution of the 3-hydroxypropionate bicycle and recent transfer of anoxygenic photosynthesis into the Chloroflexi. Proceedings of the National Academy of Sciences, U.S.A. published online before print.