Photosynthesis is the source of all food and most energy resources on Earth, as well as the oxygen that we breathe. Plants perform photosynthesis, but they are only able to use a small fraction of the light that comes from the sun, bounded within the visible part of the spectrum, i.e. light that we are able to see. Light at wavelengths longer than 700 nm are invisible to both us and plants, but there are photosynthetic bacteria that exist that are able to capture and use wavelengths past 1000 nm. They are able to do this because of the specialised pigments that they use to capture the light, and the proteins that bind these pigments and hold them in place. By understanding how these organisms capture this energy, it may be possible to combine their pigment/protein systems with those used by plants to create organisms that are able to use a much broader range of the solar spectrum, thus making the process of photosynthesis more efficient.
Improvements in photosynthetic efficiency could lead to the improvement of crop yields and growth season lengths, an important approach to tackling the increasing food and fuel shortage that is occurring with an ever-expanding world population.
The objectives of EngiNear-IR are to complete the pigment biosynthesis pathways for chlorophylls and carotenoids found in nature, and to engineer modified proteins to house these pigments in photosynthetic cells, in order to develop complexes that are able to capture underutilised wavelengths of light between 700-1000 nm.
At the conclusion of the project the pathways for the biosynthesis of all of the photosynthetic pigments in green sulfur bacteria have been solved, and this work has provided avenues for the completion of the same pathways in purple bacteria. We also have a greater understanding of how photosynthesis evolved to extend into the near-infrared, guided by the arrangement and packing of chlorophylls in light-harvesting complexes, which will inform the engineering of new strains of bacteria that can be harnessed for biotechnological purposes, and the design of biohybrid and synthetic light-capturing devices for sustainable energy production. I was also involved in work that discovered the enzyme used to synthesise chlorophyll f, that some specialised cyanobacteria use to perform photosynthesis in far-red light; modification of plants to use this pigment could result in greater crop yields and season lengths, providing more food to an increasingly populated planet.
