Axenic Biofilm Formation and Aggregation by Synechocystis sp. Strain PCC 6803 Are Induced by Changes in Nutrient Concentration and Require Cell Surface Structures

Microbes can exist as suspensions of individual cells in liquids and also commonly form multicellular communities attached to surfaces. Surface-attached communities, called biofilms, can confer antibiotic resistance to pathogenic bacteria during infections and establish food webs for global nutrient cycling in the environment. Phototrophic biofilm formation is one of the earliest phenotypes visible in the fossil record, dating back over 3 billion years. Despite the importance and ubiquity of phototrophic biofilms, most of what we know about the molecular mechanisms, genetic regulation, and environmental signals of biofilm formation comes from studies of heterotrophic bacteria. We aim to help bridge this knowledge gap by developing new assays forSynechocystis , a phototrophic cyanobacterium used to study oxygenic photosynthesis and biofuel production. With the aid of these new assays, we contribute to the development ofSynechocystis as a model organism for the study of axenic phototrophic biofilm formation.