Enhancing and Redirecting Cyanobacterial Electron Flow (Bioelectricity Spotlight)

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The movement of electrons within cells is fundamental to life, and drives the processes that happen inside cells. For photosynthetic organisms, the movement of electrons can be powered by sunlight, and for all organisms it can be powered by the metabolism of compounds in food. The electrons can be used within cells in the synthesis of useful compounds. Some of the electrons can leave the cells, resulting in electric currents that can be harvested and used as a source of renewable energy. We have shown this is possible with photosynthetic bacteria (also known as 'blue-green algae' and 'cyanobacteria'). They can use sunlight to produce external electric current. We have succeeded in using the currents from these bacteria to drive a microprocessor - highlighted in the news media as 'algae-powered computing'. One of our long-term goals is to find ways to increase the electrical currents produced by photosynthetic bacteria, inside the cell or outside. However, we know little about what determines how many electrons are available, and how the electrons get to the outside of the cell. This makes it difficult to improve the process in a directed, rational way. We have recently developed a way of screening large numbers of photosynthetic bacterial cells for ones that have genetic changes (mutations) increasing electron availability. This exciting step forward allows us to find cells with improved electron availability without having to make assumptions in advance about how the process works. We will obtain improved cells, and then determine what the mutations responsible are. We will measure the ability of the improved cells to produce currents outside the cell, and to synthesis novel compounds inside the cell. This will be be important for biotechnological exploitation of this 'microbial electricity', and also help us to answer biological questions about what limits the movement of electrons.