Cyanobacteria or blue green algae encompass a large and heterogeneous group of photosynthetic bacteria found in many terrestrial and aquatic environments, which play a major role in the global carbon and nitrogen cycles. These organisms are increasingly exposed to a number of environmental stresses as a result of pollution and ocean acidification. Thiols, small molecules, containing a characteristic sulfhydryl group, are key protectants against environmental stresses. In particular, thiols react with the amino acid cysteine in proteins, in a process called thiolation, and protect these amino acids from irreversible inactivation by oxidative stress. It has long been known that cyanobacteria contain a thiol called glutathione; however, recently another thiol, ergothioneine, has been identified in cyanobacteria. This project explores the role of glutathione and ergothioneine in cyanobacteria. First, in an undergraduate microbiology course, a survey of thiols in species of cyanobacteria, isolated from terrestrial, marine, and freshwater environments will be undertaken to provide a comprehensive view of thiols in cyanobacteria. Second, the function of glutathione and ergothioneine will be studied in the model cyanobacteria, Synechocystis PCC6803 and Synechococcus PCC7942, with the use of mutants lacking glutathione, ergothioneine, or both thiols. These mutants will be exposed to various environmental stresses to see how well they deal with them. Identification of proteins that require glutathione and ergothioneine as cofactors will be attempted and proteomics will be performed to determine which cyanobacterial proteins are protected by thiolation during environmental stress. The ultimate aim of this research project is to evaluate the relative contribution of different thiols in cyanobacteria in protecting the cells against environmental stresses.
Broader Impacts This research will be performed by undergraduate and Master's level graduate research assistants, working on research projects and in project oriented learning classes in molecular biology and microbiology. The students will present their research findings to K-12 students in elementary/high schools as a service learning exercise. Elementary and high school teachers will be involved in this project through molecular biology workshops or through mentored research experiences in the PI's laboratory. This project will shed light on how photosynthetic bacteria cope with changes in their environment and may provide insight into how global climate change might influence cyanobacterial populations.