Media release

From: Springer Nature

Chemistry: Radiation resistance from manganese antioxidants may have promoted life on early Earth

Cell-like structures that contained manganese antioxidants resistant to gamma radiation may have existed on primitive Earth, allowing for the evolution of life, according to a model published in Nature Communications. These findings shed light on how early cells may have protected themselves from radiation damage during evolution.

The first cells, called protocells, were thought to have possibly emerged under extreme conditions on early Earth, known to have much higher radiation levels compared to current levels. However, it is unclear how protocells were protected from destruction by radiation, which causes the production of reactive oxygen species that damage biological molecules. Previous studies have shown that polyphosphate — a chain of many phosphate residues — and manganese ions protect against oxidative stress in the bacterium Deinococcus radiodurans, which is also resistant to high doses of gamma radiation.

Bing Tian and colleagues report a radioresistant protocell model comprised of two main types of coacervates (liquid droplets that model protocells): polyphosphate-manganese coacervates and polyphosphate-peptide coacervates. They exposed them to high levels of gamma radiation that may have existed on primitive Earth and found that the polyphosphate-manganese coacervates stayed intact and were able to protect the recruited proteins, whereas the polyphosphate-peptide coacervates were destroyed. The authors suggest that radioresistance is mediated by the ability of manganese antioxidants to scavenge reactive oxygen species. The authors then assembled a polyphosphate-manganese coacervate with polyphosphate-peptide and DNA coacervate in a cell-like structure. They found that the polyphosphate-manganese cytoplasm (the liquid that fills the inside of the cell model) was able to protect the peptide and the DNA-containing nucleus from radiation damage.

The findings may provide a mechanism for the radiation protection of early cells and the biological molecules within them, which could have aided protocell evolution into present-day cells, the authors suggest.