The bacterium Shewanella oneidensis uses a large number of electron acceptors for respiration. These include insoluble metal oxides and toxic metals such as uranium and chromium, in addition to common electron acceptors such as oxygen. The large number of c cytochromes it produces under anaerobic conditions facilitates the respiratory versatility of S. oneidensis. The cAMP-receptor protein CRP regulates anaerobic respiration in S. oneidensis. Although CRP regulates a large number of cellular processes in other bacteria, its ability to regulate anaerobic respiration is unusual. Redox sensing domains needed for such a function are not present in CRP. This project investigates the mechanisms that lead to CRP activation under anaerobic conditions. The role of two adenylate cyclases that synthesize cAMP needed for formation of an active CRP complex will be examined. One adenylate cyclase, CyaC, is a membrane-bound protein similar to eukaryotic adenylate cyclases involved in signaling. The prediction that CyaC plays a role in redox sensing will be investigated. The effect of environmental signals, such as oxygen depletion, on expression and activity of adenylate cyclases will be measured. A genetic screen will be used to identify specific regions of CyaC that are important for activity and/or redox sensing. The information obtained will elucidate novel mechanisms that control anaerobic respiration, including metal reduction. Metal reducers are potential bioremediation agents due to their ability to detoxify metals during anaerobic respiration. Results from this research will further the understanding of the mechanisms that regulate metal reduction, and could result in strategies to artificially stimulate bioremediation of toxic chemicals. The project includes the training of graduate and undergraduate students in fields of microbial and molecular biology.
