For the field of synthetic biology, the adaptation of principles, from the well established traditional engineering
disciplines, like mechanical and electrical engineering, in order to realise complex synthetic biological
circuits, is an intriguing prospect. These principles can enable a forward engineering, rational design and
implementation approach, where a system's properties can be predicted or designed in silico followed by the
manufacturing of the in vivo system, that can be tested, used or redesigned in the most efficient possible
way. Achieving control over these circuits, is one of the important topics of the field, for these applications to
become robust and render useful functions applicable to energy, medicine, pharmaceuticals and agriculture
industries. In this work, I attempt to explore light, as a promising control 'dial' for synthetic circuitry. Light is
fast, economic compared to chemicals, it can be interfaced with electronics, it is reversible in its effect and
can be applied at a fine spatio-temporal resolution. These characteristics, are absent from the classically used
chemical inducers, meaning that light, can open new possibilities for the user to control synthetic systems, or
even facilitate the cell to cell communication, within population based networks.
This work, is a contribution towards harnessing the advantages of light, for achieving control over synthetic
circuits. More specifically, I start with the detailed theoretical and experimental study of the Cph8 two
component system, a synthetic chimeric receptor which is responsive to red light. This is done, in order
to develop a sufficient theoretical understanding of it, through detailed mechanistic modelling, in order
to connect the specific system with the toggle switch and the dual feedback oscillator, in an optimal way
and achieve control of these devices through light. The developed model, was able to highlight the main
aspects and mechanisms inherent to its structure, describe most of the observations from the experimental
system, to also make quantitative predictions. The second part of this work, was the development of novel
promoters, that can be regulated by a commonly used transcription factor, such as LacI, but also, light
responsive regulators like OmpR and CcaR. This yielded a direct way to integrate light and chemical inputs,
into a single output, while the dual regulation, allowed to connect and modulate the toggle switch without
the need of additional transcription factors. The latter, a light tuneable toggle switch, showed indications that
it can function as a memory controller that can be reset by light. Finally, I show the design and modelling of
a light tuneable dual feedback oscillator, where light of one wavelength can be used to tune the amplitude,
while another wavelength can tune the period. The developed models and synthetic circuits are expected to
contribute towards implementing finely tuned and controlled synthetic circuits through light.Open Acces
