Ultraviolet Radiation and Salinity-Induced Physiological Changes and Scytonemin Induction in Cyanobacteria Isolated from Diverse Habitats

Enhanced ultraviolet radiation (UVR) in the atmosphere and increased salinity of soils and water adversely affect photoautotrophs' productivity. Several researchers have focussed on the use of non-arable or brackish environments for growing strains suitable for the production of value-added products along with biofuels. In this regard, cyanobacteria serve as good model organisms as they can survive and sustain themselves in habitats characterized by high UV influx and changing salinities. Thus, these photoautotrophs can help understand the complex physiological processes and adaptations occurring in higher plants growing in stressed environments of salinity and UVR. In the present investigation, cumulative effects of salinity (NaCl: 50, 100, and 200 mM), photosynthetically active radiation (PAR), and UVR have been studied in terms of the reactive oxygen species (ROS) generation, total protein content, phycobiliproteins profile, and induction of scytoneminin in the two cyanobacteria isolated from different habitats. Production of ROS increased after PAR+UV-A+UV-B, PAR+UV-A, and PAR exposure, and maximum generation occurred in the samples treated with 200 mM NaCl. Total protein content and phycobiliproteins profile was severely affected by these stresses. The maximum induction of scytonemin occurred in the cultures with 200 mM of NaCl and PAR+UV-A+UV-B exposure for 72 h. Our results indicate that Scytonema sp. could serve as a potential candidate for bioremediation of saline soils along with the production of value-added metabolite scytonemin.

Automated summary

Enhanced ultraviolet radiation and increased salinity negatively impact the productivity of photoautotrophs. Cyanobacteria, known for their ability to survive in high UV environments, are valuable for studying plant adaptations to salt and UV stress. Research on the effects of salinity, radiation, and UVR on two cyanobacteria species showed increased ROS production and significant protein and pigment profile changes under stress conditions.