Cyanobacteria Under UV Radiation: General Insights into Stress Responses.

One of the first organisms to appear on Earth was cyanobacteria, which carried out oxygenic photosynthesis. The oxygen they produced contributed to the ozone layer's formation. However, before this happened, cyanobacteria had to cope with various forms of radiation, including ultraviolet radiation (UVR), that reached the surface of young Earth. Billions of years ago, before the Earth's ozone layer formed, the planet was constantly exposed to intense UVR. This radiation, especially UVB and UVC, was strong enough to break down proteins and nucleic acids. Cyanobacteria have a variety of defence mechanisms that allow them to thrive under adverse conditions. These mechanisms include the avoidance of UVR through migration or mat formation, DNA repair, antioxidant enzyme activity, and biosynthesis of UVR-absorbing compounds. Although most of today's dangerous UVR is absorbed by the ozone layer, future space exploration has led to a closer examination of the effects of UVR, especially UVC, on various organisms, including cyanobacteria. The flexibility of cyanobacteria to tolerate unfavourable conditions makes them potential candidates for future space exploration. This brief overview provides some information on the effects of UVR on cyanobacteria, the defence mechanisms of cyanobacteria against UVR, and the potential use of cyanobacteria in life-support systems in space missions.