Plug'n Play Photosynthesis for Rubisco Independent Fuels

Supplying the world's energy needs with a clean, renewable fuel is perhaps the most pressing scientific and political challenge facing humanity. The solar energy hitting the earth's surface is more than sufficient to fulfill these needs. In fact, our current economy is predicated on the burning of cheap fossil fuels, relics of ancient photosynthesis. Unfortunately, our rate of use of these fuels far outstrips their production, and is also producing carbon dioxide at potentially environmentally acceptable rates. Thus, it has become essential to develop new routes to directly produce chemical fuels, i.e. energy storage molecules, from solar energy. Biological systems solved this problem through the development of photosynthesis. However, organisms have been evolved for biological fitness, not for human fuel production. Under high light conditions, RuBisCO, the enzyme catalyzing the rate limiting step in CO2 fixation, becomes saturated. Under those conditions, the Calvin Cycle becomes down-regulated and the majority of light energy absorbed is lost as heat. New strategies are needed to improve utilization of this light energy to produce fuels. Our strategy to solve this problem is to create a trans-cellular, plug-and-play platform that allows us to shunt electrons from photosynthetic source cells to independently engineered fuel production modules along nanowires (these could be microbial based, partly or even totally synthetic). The project represents a radical approach to augment and surpass photosynthetic strategies observed in Nature by engineering modular division of labor through electrical connectivity

Photosynthetic cyanobacteria will be engineered to heterologously express electrically conductive pili, or 'wires' derived from bacteria such as Shewanella sp. pili will be investigated microscopically and electrochemically to characterize both anatomy and electrical properties. In the second phase, regulatory mechanisms will be introduced into the phototroph to allow controlled shunting of electrons away from ordinary metabolism. This will allow coupling to fuel production units, which will be developed to operate in chemotrophic organisms (linked to the phototroph via the conductive biowire. Initial studies will be undertaken with natural enzymes (hydrogenase and formate dehydrogenase) and studies will progress to an artificial CO2 reducing construct and well as alkane producing pathways.

Ensuring a stable energy supply is the central challenge of the 21st century, and this team will highlight the importance of the problem and prepare the next generation of scientists. In additional to the technical goals, this project is envisaged to have broader impacts in four distinct domains: 1. The successful completion of the scientific goals of this program will transform thinking about photosynthesis by creating independent modules for studying and optimizing the light and dark processes as well as portable biowires to establish functional contacts between distinct cell types. These modules, as well as the platform for testing them as a system, will be freely shared with other researchers. 2. Students will be important stakeholders in the Plug and Play (P&P) team and funds have been included for all American PIs to include summer, undergraduate students in their research. Furthermore, the proposed project offers extraordinary training opportunities to students at all levels. Unique to this project and multidisciplinary team is the range of scientific disciplines and academic institutions involved. In particular P&P includes representatives from the fields of microbial ecology, synthetic biology, protein biochemistry, protein design spectroscopy, electrical engineering and bioinorganic chemistry, and its members work in labs in seven universities in the U.S. (Arizona State, Michigan State, Penn State, Emory) and the U.K. (Glasgow, Southampton, Imperial). 3. The P&P team exemplifies the globalization of science and will serve as a model for collaboration between the NSF and the BBSRC. Recognizing the importance of international collaboration, we have carefully constructed a trans-Atlantic administrative structure to foster close ties and included funds in the budget to support exchange of scientific personnel between laboratories. 4. Dissemination of scientific results will be crucial to this project, both to push the boundaries of photosynthetic research and engage the public in understanding a crucial problem. The geographic disparity of the participants provides a unique opportunity to develop web-based photosynthetic resources to engage the international community.