Figure 1 A Textile Cone Snail (Conus textile)
Location: Cod Hole, Great Barrier Reef, Australia
Photographer: Richard Ling (CC-BY-SA 3.0)

What if these surprising patterns on sea snail shells would come from a simple rule, followed by all subsection on the shell?

For example in the picture below, you can see that a similar pattern can be produced by already a simple rule, in which every cell decides on its state (white or green) depending on the state of the 2 cells above it. This rule is called an XOR gate: If one of the two cells above is ON, the cell below them is ON, if both cells above are ON or if both cells above are OFF, the cell below is OFF.

As a matter of fact, many of the complex patterns you can see in nature come from simple rules. It is the case for hurricanes, flocks of birds, neural networks etc. We call this phenomenon emergence. Emergent phenomena are not predictable from the initial conditions and this is why they surprise us. If you are interested in emergence of complexity in general, you can read more about the background of our project.

As a team, we are driven by our fascination for the emergence of complexity and try to make these snail shells patterns, called Sierpinski triangles, emerge on our own grid of bacteria. To achieve this goal we encode the rule that leads to emergence of these patterns in the DNA of these bacteria. This approach, defined Synthetic Biology, is the application of engineering principles to the fundamental components of biology. Here we are using information processing principles in order to control the path of the information through all cells.

This way, Mosaicoli not only endeavors to learn more about how a complex pattern can emerge from simple rules, but also develops new tools for controlling communication between cells and implementing reliable biological circuits. For a more detailed description of our goals, go to the Goals section. For an outlook on the possible applications of our project, jump directly to Applications and outlook.

More details

• to sense the signals coming from the two cells above.
• if it senses only one signal, to produce a fluorescent protein and generate the signal for the cells below
• to produce nothing if it senses both signals or if it does not sense any signal.

In synthetic biology, you can tell the cell to compute this algorithm by inserting a genetic circuit. Here is how we did it:

• For sensing the signals coming from above, we added in every cell two genes (luxR and lasR) that produce two proteins (LuxR and LasR) that will bind respectively the blue and the red quorum sensing molecules of the figure above. The blue and red complexes created this way trigger the production of other proteins called integrases (Bxb1 and ΦC31). Integrases flip a DNA sequence between two flanking sequences called att-sites (the triangles in the animation above).
• This sequence between att-sites (see the large, black T in the animation above) is placed in such a way that it blocks production of a fluorescent protein. Once an integrase is present, the DNA sequence is flipped and production becomes possible. You can see in the animation that if an integrase is present, it can remove this blocking sequence (turn the black T upside down). However if both integrases are present, this sequence is flipped twice and it blocks production of fluorescence again.
• When the fluorescent protein is produced, a second protein is produced as well which triggers the production of a quorum sensing molecule sent to the cells below.

If you want to know more about quorum sensing and integrases, you can read the article Biological tools in our Background page.