Team:TU Delft/Proof
Functional proof of concept
Maybe some title??
When making biological lenses, the shape of the lens is of crucial importance. E. coli is a rod-shaped organism, so it’s not symmetrical along all axes. Shining light on the round parts of E. coli has a different effect on the focusing of light than shining light on the long sides, see figure 1 add this figure??. More information on this can be found on the modeling and project pages.
For some applications, such as the solar cells, this variation in shape does not matter that much; here it’s most important that light gets focused in any way Modify this so it makes sense to do this. However, when we want to use our microlenses in more advanced optical systems, such as microscopes or cameras, we need to make sure that this variation between the different lenses is minimized. Manufacturers of optical systems do not accept a high aberration between different lenses, so it’s crucial for us to be able to control the shape of our lenses. We have decided to engineer E. coli in such a way that it becomes spherical. This way we are able to create spherical lenses. Apart from the fact that it is crucial to be able to control cell shape, round cells offer the advantage of being symmetrical along all axes, so the orientation of your lens does not matter for the optical properties.
To produce round shaped biolenses we need our E. coli to perform two special activities: produce the biolens itself and change its shape from rod to round. As it is described in the project page in more detail, to be able to obtain biological lenses we need a coating of polysilicate, biological glass, around the cell. This glass will give optical properties for the cell. E. coli is intrinsically not able to coat itself in polysilicate. However, upon transformation of the silicatein-α gene, originating from sponges, it is possible to coat the bacterium in a layer of polysilicate (Müller et al., 2008; Müller et al. 2003). Therefore, we are transforming E. coli with silicatein-α. We test the use of silicatein from two different organisms expressed in three different ways, of which the most successful one was the construct consisting of silicatein from Tethya aurantia fused to the membrane protein OmpA (Part K1890002) as shown by Rhodamine123 staining and other imaging experiments (see project page).
In order to create spherical E. coli, we overexpress the BolA gene. BolA is a gene that controls the morphology of E. coli in the stress response (Santos, Freire, Vicente, & Arraiano, 1999). By overexpressing this gene, the rod-shaped E. coli cells will become round (Aldea, Hernandez-Chico, De La Campa, Kushner, & Vicente, 1988). We will express this gene both under a constitutive promoter (Part K1890031), as well as an inducible promoter (Part K1890030), the latest being our favorite due to the better result obtained (see project page). When we express both the BolA gene as well as silicatein, we are able to construct round cells, coated in glass.
