Towards designing synthetic molecular motors: in situ visualization of the progressive evolution of molecular gearing by bacteria

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We are entering a new era in which we will make our own tiny 'nanoscale' machinery. We hope that this machinery will produce food, fuel, and clean water, help fight disease, accurately read and write information to DNA, and perform emission-free mechanical tasks. Recent successes have come from using machines that have evolved inside microbes in making chemicals using living cells and storing information in DNA, but we haven't done much work to make our own "molecular motors" that perform physical tasks inside cells. This is mainly because we've been limited by our techniques: we haven't been able to see the machines that have naturally evolved inside cells over the billenia, so we've found it difficult to understand how they work or evolved - and how to do it ourselves (instead we've had to break open cells and purify the machines to study them, a process that often badly affects the machinery that we're trying to study). Thankfully recently we've developed ways to to image machines in 3-D inside cells by freezing the bacteria and putting them in an electron microscope. I recently trained to use this new technology. I've used it to study probably the most captivating example of molecular motors, a motor that spins a spiral-shaped propellor (the "flagellum") to push bacteria in good directions. But the flagellar motor is more than just a fascinating example of the wonders of life on earth, and studying it promises many useful things to us. One use would be to work out how to harness its emission-less power. A single motor from E. coli (a very well studied bacterium), if it were the man-sized, would be as powerful as an airplane turboprop engine! It has been known for some time that different motors are stronger or weaker than the E. coli motor, but we don't know why because we haven't been able to see them. This all changed when we used the new technique for imaging whole cells to look at a wide range of bacteria to see their motors. A bacterium called Campylobacter jejuni, or just "Campy", struck us as interesting: not only was it known to swim through very sticky fluids better than other bacteria, but the part that generates rotation is bigger than other bacteria, which we think makes a stronger motor that helps Campy swim. What makes this particularly interesting is that Campy has evolved this adaptation. If we could understand how it did this, we might try to copy it to modify motors to our own specifications. Then we might control bacteria to ferry cargoes around, selectively seek and destroy cancers cells, push miniature rotors, or mix fluids together.I aim to collect data to fully understand how the Campy motor evolved. To do this I'll image Campy, and simultaneously alter the DNA to change the appearance of the motor. In this way we'll be able to work out where parts of the motor are. At the same time I'll image a bacterium that looks like it's halfway between Campy and E. coli to see if this "half-way" cousin tells us anything about the evolutionary pathway that Campy had to follow. Finally we'll take each part of the motors from all of these bacteria and use their DNA sequences to work out their ancestry. This will help us to see where the Campy motor recruited the additional parts that it uses to be more powerful.As well as these aims I'm planning on developing methods to work out which parts of the motor go where. To do this I'm going to develop computer programs to design better ways to 'tag' components of the motor with extra bits. These extra bits will be easily visible in the 3-D structures that we collect, enabling us to directly visualize where the tagged components are. Indeed, if this works out it will open the next chapter: instead of using these tags to understand the motor, we'll use them as modifications that we can improve by directing evolution. Maybe someday we'll have a motor that we can gear as we wish.