Engineering new capacities for solar energy utilisation in bacteria

光合作用捕捉阳光的力量，推动陆地上植物和海洋中单细胞细菌和浮游生物的生长，支撑着所有全球食物链，并提供我们呼吸的氧气。由于我们的地球大部分被水覆盖，基于水的光合细菌的数量和活性是惊人的;每年有数十亿吨光合细菌在海洋中生长。这些细菌必须相互竞争阳光，并且已经进化到生活在不同的深度和环境中，甚至在地表以下100米或更深的极端条件下生长。太阳光是由许多不同颜色的光谱组成的，不同的细菌进化出了特殊的化学物质，称为色素，可以吸收光谱中的特定颜色。光合作用的未来生物技术应用可能需要含有多种色素的多色细菌，这些细菌可以获得比进化所要求的更多的太阳光谱。这样他们就可以利用更多的太阳能来制造对人类有用的化学物质。实现这一目标将意味着把来自不同细菌的色素“混合匹配”在一个细胞内。现在这是可能的，因为我们已经发现了光合细菌是如何制造每种类型的色素的-叶绿素，细菌叶绿素，胆色素和类胡萝卜素。他们通过使用一套叫做酶的生物机器来实现这一点，这些机器在一条叫做生物合成途径的生产线上共同工作。我们已经发现，我们可以通过组合来自一种以上光合细菌的酶的遗传密码来创建新的色素生物合成途径。这让我们更多地了解了天然酶和途径是如何工作的，能够建造或制造东西是对你是否理解它的最终考验。本研究计划的第一部分将在光合细菌中创造新的途径和色素组合。第二部分将研究这些新的色素组合如何在电池内部和仿生硅芯片上共同吸收太阳光谱中的新颜色。第三部分开始转化细菌细胞如大肠杆菌的过程。大肠杆菌是无色的，和人类一样靠呼吸氧气生存，它进入光合作用细胞。要做到这一点，最简单的方法是从海洋细菌中引入一种原始的光能蛋白质，称为变形视紫红质，但我们也将开始更雄心勃勃的大规模E。大肠杆菌和类似的细菌，因此它们可以制造细菌叶绿素、胆色素和类胡萝卜素色素。这种电池将有内部太阳能电池板，使他们能够第一次使用阳光。这些光动力细胞工厂在未来的生物技术和生物能源应用中具有巨大的潜力，例如生产酒精，烷烃和新型药物。在本研究计划的最后一部分，我们将采用一些已经有用的东西，在这种情况下，光合细胞可以制造生物柴油，并使用我们的色素生物合成工程，使它们更有效地利用光来驱动生物柴油的生产。我们将去寻找新的色素生物合成基因，因为我们只触及了海洋中色素途径基因数量的表面。新的基因可以通过一台机器来发现，这台机器可以看到细胞的颜色，并从海水中取出有价值的单个细菌，这样就可以对它们的DNA进行测序，以寻找新的色素途径。我们希望利用我们发现的基因，以及我们已经知道的基因，来构建能够捕获和利用太阳能的新细菌。这一知识对我们所有人都很重要，不仅因为捕获和使用太阳能为生命提供燃料，而且它还掌握了使用电池的秘密，有朝一日可以为我们提供清洁，无限的能源和来自阳光的宝贵化学物质。

Photosynthesis captures the power of sunlight to drive the growth of plants on land and single-celled bacteria and plankton in the oceans, underpinning all global food chains and providing the oxygen we breathe. Because our planet Earth is mostly covered in water, the quantity and activity of water based photosynthetic bacteria is stupendous; billions of tonnes of photosynthetic bacteria grow in the oceans every year. These bacteria have to compete with each other for sunlight, and have evolved to live at different depths and environments, even growing in extreme conditions 100 metres or more below the surface. Sunlight is made up of a spectrum of many different colours of light and different bacteria have evolved specialised chemicals called pigments that absorb a particular colour of the spectrum.Future biotechnological applications of photosynthesis are likely to require multicoloured bacteria containing multiple pigments that can harvest more of the solar spectrum than evolution has demanded of them. That way they could use more solar energy for making chemicals useful for man. Achieving this would mean putting together 'mix and match' combinations of pigments from different bacteria inside one cell. This is now possible because we have been finding out how photosynthetic bacteria make each type of pigment - chlorophylls, bacteriochlorophylls, bilins and carotenoids. They do it by using sets of biological machines called enzymes that work together in a production line called a biosynthetic pathway. We have found that we can create new pigment biosynthesis pathways by combining the genetic codes for enzymes from more than one type of photosynthetic bacterium. This teaches us more about how the natural enzymes and pathways work and being able to build or make something is the ultimate test of whether you understand it.The first part of this research programme will create new pathways and combinations of pigments in a photosynthetic bacterium. The second part will find out how these new pigment combinations work together to absorb new colours of light from the solar spectrum both inside the cell, and on biomimetic silicon chips. The third part starts the process of converting a bacterial cell such as E. coli, which is colourless and lives by respiring oxygen the way humans do, into a photosynthetic cell. The simple way to do this is by importing a primitive light-powered protein called proteorhodopsin from oceanic bacteria, but we will also begin the more ambitious large-scale genetic engineering of E. coli and similar bacteria so they can make bacteriochlorophyll, bilin and carotenoid pigments. Such cells will have internal solar panels that allow them to use sunlight for the first time. These light-powered cell factories have great potential for future biotechnology and bioenergy applications such as the production of, for example, alcohols, alkanes and novel pharmaceuticals.In the last part of this research programme we will take something that is already useful, in this case photosynthetic cells that make biodiesel, and use our pigment biosynthesis engineering to make them more efficient at using light to drive biodiesel production. We will go prospecting for new pigment biosynthesis genes, since we have only scratched the surface in terms of the number of pigment pathway genes out there in the oceans. New genes can be found using a machine that sees the colour of cells and plucks valuable single bacteria out of seawater so their DNA can be sequenced to look for new pigment pathways. We hope to use the genes we discover, as well as the genes we already know about, to build new bacteria that can capture and use solar energy. This knowledge is important to us all, not just because capturing and using solar energy fuels life, but it also holds the secret of using cells that one day could give us clean, unlimited energy and valuable chemicals from sunlight.