A research paper describes a model showing that cell-like structures containing manganese-based antioxidants and resistant to gamma rays existed on early Earth, making the evolution of life possible.Nature CommunicationsPublished in The findings reveal how early cells defended themselves against radiation damage during evolution.
The first cells that appeared on Earth are called protocells. It was thought that primitive cells may have existed under harsh conditions on early Earth, where radiation levels were known to be much higher than they are today. Irradiation stimulates the production of reactive oxygen species, which can damage biomolecules, but it is not known how archaeal cells defended themselves against radiation-induced destruction. Previous research revealed that the bacterium Deinococcus radiodurans, which is resistant to high doses of gamma radiation, is protected from oxidative stress by inorganic polyphosphates (chains of many phosphate residues) and manganese ions.
This time, Ping Tian and colleagues describe a model of a radioresistant primitive cell, consisting of two main types of coacervates (droplets similar to primitive cells): manganese polyphosphate-based coacervates, and polyphosphate-based coacervates. Tian and his colleagues irradiated these two types of condensates with high doses of gamma rays, which are thought to have existed on early Earth, and found that the manganese polyphosphate moieties remained intact and that the proteins inside the droplets were protected. – The peptide coservates were found to have been destroyed. Tian and colleagues suggest that radiation resistance is due to the ability of manganese-containing antioxidants to scavenge reactive oxygen species. Next, Tian and colleagues assembled cell-like structures by encapsulating polyphosphate-peptide droplets and DNA-conjugated concentrates in polyphosphate-manganese-based conjugates. They found that manganese and polyphosphate-like droplets of cytoplasm, the fluid that fills the interior of model cells, can protect the nucleus, which contains peptides and DNA, from radiation damage.
Tian and colleagues believe that the above findings point to a mechanism that protected early cells and their internal biomolecules from radiation, and that this mechanism may have supported the evolution of primitive cells into modern cells. It is reported that this exists.
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