INVESTIGATING THE ROLE OF MODEL CYANOBACTERIAL BIOFILM CONSTITUENTS IN ABIOTIC STRESS RESILIENCE

The major goal of this project is to better understand the biological underpinnings of abiotic stresstolerancerelatedtosecreted extracellularpolymeric substances (EPS) in cyanobacteria. EPS are positively implicated in protective biofilm formation and stress response, but their modulation or compositional variance related to stress has not been evaluated. To best assess this, we will modulate EPS production and composition by genetic engineering of a model cyanobacterium, Synechocystis PCC 6803 (S. 6803), that natively produces little EPS or biofilm and exhibits poor baseline abiotic stress tolerance. Mechanisms of abiotic stress tolerance are important to study towards developing adaptive, resilient agricultural solutions to safeguard both crops and soils in the face of global climate change related stresses, such as drought and temperature.The first objective of this study is to generate unique, targeted S. 6803 genetic mutants with altered EPS and improved biofilm tendency. We will pursue five identified genetic targets likely to yield phenotypes of interest. We will then compare mutant viability under abiotic stress, such as drought, temperature, pH, high UV, or high salt with the unaltered S. 6803 wild type (WT).The second objective of this study will elucidate biological mechanisms of stress resilience in EPS and biofilm modulated mutants. To ascertain how stress resilience is conferred to mutants, the top three genetic targets that show enhanced tolerance under a stress condition from the first objective will be combined and reassessed for stress tolerance both separately and in combination and compared with WT. Stressed vs unstressed mutants as well as mutant vs WT under stress are likely to show different EPS and gene expression profiles, so we use these methods to uncover potential different mechanisms of abiotic stress tolerance.