Enhancing photosynthesis by engineering metabolic cooperation in microbial consortia.

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John Heap, Travis Bayer

Imperial College London, United Kingdom

Photosynthesis is the primary source of energy and organic carbon for almost all life on Earth, and the ultimate source of feedstocks for many existing and possible future industries. Two processes are involved: the capture and storage of light energy, which occurs rapidly; and the use of that energy to fix CO2 from the atmosphere, which is a much slower process. The mismatch between light capture and carbon fixation means that photosynthesis is inefficient under typical high-light, carbon-limited conditions. This problem is compounded in populations of microbial photoautotrophs, where most cells receive either more light than they can use, or too little light to fix carbon (they are shaded by other cells). We have engineered a microbial consortium to perform photosynthesis in cooperative manner, exporting excess energy in the light and importing energy to fix carbon in the dark. Crucially, there is no net transfer of carbon between cells, so the transfer mechanism is not constrained by the supply of fixed carbon. This ‘distributed photosynthesis’ strategy could increase the carbon-fixing capacity of a photosynthetic population, and is unlikely to have been explored by natural selection, unlike conventional efforts to improve carbon-concentrating mechanisms or the key rate-limiting enzyme RuBisCO.