We have chosen light stimulus as our input for the Biofabricator. Light allows us to generate complex patterns with well defined edges, while gradients in wavelength and intensity will allow us to build up varying concentrations of biomaterial.
Photoreceptors and domains that were considered in our design include rhodopsins, phytochromes, LOV and BLUF. Of these, B. subtilis contains the blue light sensing protein YtvA which is related to the plant blue-light receptors phototropins. YtvA is a positive activator of the general stress transcription factor σB. Blue and not red light activates YtvA and thus induces σB activity. We could use σB which is expressed upon blue light illumination to activate the production of EpsE and hence control bacteria motility. However, there are other stressors which activate σB, hence we aim to make blue light the main activator of σB by controlling growth conditions and over expressing the YtvA receptor.
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