Our laboratory employs genetic approaches and cutting-edge molecular tools to study mechanisms allowing cyanobacteria to sense changes in the environment and survive under a large variety of conditions. Cyanobacteria had, and still have a substantial impact on life on earth. Being the first organisms that performed ‘oxygenic photosynthesis’, cyanobacteria had a pivotal role in the history of life by changing the chemistry of the atmosphere and allowing the development of aerobic eukaryotes. Furthermore, cyanobacteria are considered the ancestors of chloroplasts of algae and higher plants. Currently, the central ecological importance of cyanobacteria is manifested in their significant contribution to global CO2 fixation (25-30% of global CO2 fixation is attributed to cyanobacteria). Additional major environmental impact stems from cyanobacterial blooms, which affect the entire food chain, and in cases of ‘toxic blooms’ cause the collapse of large aquatic ecosystems and impact the quality of water reservoirs. Our studies of cyanobacterial stress physiology and the molecular mechanisms underlying it, provide insight into fundamental cellular processes, e.g. regulated proteolysis and multicellular behavior of bacteria.