Abstract

Modern "lithography" has made images vividly printed on pages and animations vigorously projected on screens. From that point, we move a step forward. Our project aims to conceive and construct a colorful bio-imaging system, on which once you project an image, ideally, the bio-system would exactly print it out on the substrate. To accomplish this, novel bio-bricks (light sensors & color printers), Caulobacter crescentus (a type of sticky bacterium) and riboswitches were utilized to conceptually make the system colorful, clear and compact. The results did prove this idea sound in principle, although further evaluation is required. We have managed to build light sensing circuits of three colors and a motion control device in C.crescentus. Furthermore, RNA logical gates were built in vivo as potential substitutes for certain parts of the system with hopefully unprecedented effectiveness.

Circuit Design

According to the blueprint of our project, we want C.crescentus to work like this:The thallus which contains whole light system and regulator system are dispersed in the liquid environment. When there is no light, the photosensitive element of the light system doesn’t work. So the downstream part expresses CI protein to inhibit the promoter of fluorescin. The cell won’t give out light. At this time, we hope that the cells are still drifting in the liquid and don’t start adhering. So for the three proteins mentioned above, we hope the two, DgrA and DgrB, which inhibit the flagellum’s motion don’t express and the holdfast synthesis profiling can express normally. On this occasion, we can keep C.crescentus a swarmer cell.

When the cells are exposed to the light, inhibition of fluorescin expression is released. We can know this from the circuit of Color Part. Now we want to reverse the switch of three proteins’ expression. That means we want to express DgrA, DgrB and close HfiA. If so, when cells sense the light, the rotation of flagellum will stop because of DgrA, DgrB and at the same time, the inhibition of holdfast synthesis will also be released. According to this principle, the cell will stop moving under light and start adhering. This will help the formation of patterns.

Now we can see, the photosensitive elements belong to the upstream system. On the other hand, the above three proteins and the luminous element belong to the upstream system. On these grounds, we put the promoters of three proteins and the promoters of luminous element correspond to realize the regulation of light on the luminous element and moving regulatory protein at the same time.

The diagram of our circuits is as following: