In the current review, we focus on UV-tolerant cyanobacteria
which in desert environments, are principally composed of Scytonema
and Nostoc species. These cyanobacteria live on the soil surface
and possess direct adaptive mechanisms to the desert
environment, particularly to temperature fluctuations and wet/dry
cycles. They have developed the ability to reversibly activate their
metabolism, limiting photosynthesis and growth to wet periods
when the cells are rehydrated. During hot, dry periods, the cells
enter into a quiescent state. Although photosystems I and II (PSI,
PSII) are damaged during high light and dryness, in vitro studies
have shown that PS I and PSII are self-repaired and operational
within minutes of the cell’s rehydration