Stenomitos frigidus ULC029 isolate:ULC029 Genome sequencing. Stenomitos frigidus ULC029 isolate:ULC029

Cyanobacteria inhabit extreme environments, including drylands, providing multiple benefits to the ecosystem. Soil degradation in warm drylands is increasing due to land-use intensification. Restoration methods adapted to the strong stress in drylands are being developed, i.e. cyanobacterial inoculation to recover biocrusts. For success, it is crucial to optimize the survival of inoculated cyanobacterial in field. One strategy is to harden them to be re-adapted to stressful conditions after laboratory culturing. Here, we analyzed the genome and ecophysiological response to osmotic, desiccation and UVR stress of an Antarctic cyanobacterium, Stenomitos frigidus ULC029, closely related to other cyanobacteria from warm and cold dryland soils. Chlorophyll a concentrations show that preculturing ULC029 under moderate osmotic stress improved its survival during an assay of desiccation plus rehydration under UVR. Besides, its sequential exposition to these stress factors increased the production of exopolysaccharides, carotenoids and scytonemin. Desiccation, but not osmotic stress, increased the concentrations of the osmoprotectants, trehalose and sucrose. However, osmotic stress might induce the production of other osmoprotectants, which complete pathways were found in ULC029 genome. In total, 140 genes known to be involved in stress resistance were annotated and could potentially help ULC029 under stress. Here, we confirm that the sequential application of moderate osmotic stress and dehydration, could improve cyanobacterial hardening for soil restoration, by inducing several resistance mechanisms. We also provide a high-quality genome of ULC029 and a description of the resistance mechanisms involved in the production of exopolysaccharides, osmoprotectants, chlorophyll and carotenoids; in DNA repair and oxidative stress protection.