Response of the sub-aerial cyanobacterium Scytonema millei to UV-C irradiation

Abstract

Increasing solar ultraviolet irradiation on the Earth&rsquo;s surface due to depletion of stratospheric ozone layer has raised the concern about its detrimental effect on living organisms. In this context, to understand the process of such damage, here, we studied the effect of UV-mediated stress on a primitive O₂-evolving photosynthetic prokaryote species. Precisely, we investigated the response of UV-C irradiation on the cyanobacterium <em>Scytonema millei</em> isolated from the exterior of a stone monument of Santiniketan, West Bengal. Molecular phylogeny based on 16S rRNA gene sequencing confirmed the taxonomic position of the species with other false branched filamentous cyanobacteria. Progressive condensation of cytoplasm, changes in the shape of cells/trichome and integrity of sheath of the organism was observed with increased duration of exposure to UV-C until 72 h. Higher content of scytonemin and mycosporine-like amino acids (MAAs) in UV exposed cells suggest their protective role against UV irradiation.