Technical

Pigments

We have taken advantage of just a small fraction of the chromatic diversity exhibited by nature to create some of our pigment vectors. Using both yeast Golden Gate (yGG) cloning and the versatile genetic assembly system (VEGAS), we are able to assemble and combine transcriptional units (TUs) consisting of a defined promoter (usually ~500 bp upstream of a start codon), coding sequence, and terminator (usually ~200 bp downstream of a stop codon). The resulting pigment is due to a functional multi-gene pathway.

For single gene pigments, we use a modified 2um shuttle plasmid with a marker conferring antibiotic resistance as the backbone for our pigment production. Pigment encoding genes have been taken from multiple sources, including sea anemone and coral. Antibiotic markers ensure that contaminants are unable to grow on our agar canvases (which are made with antibiotic).

This approach works equally well with fluorescent proteins (under fluorescent light).

Image breakdown and color matching

We have written two complementary Matlab scripts to generate printing instructions for the Echo liquid handling robot. Briefly, they:

1. Rescale the image of interest for the dimensions of our agar trays

2. Match each pixel to the “closest” color of yeast in our collection using a user-defined colorspace

3. Choose whether or not to print whitespace

4. Output a csv file containing information about source well, destination location, and transfer volume for each pixel

Printing

The CSV file is used to instruct the Labcyte Echo 550 liquid handler, which uses acoustics to shoot precise nanoliter droplets onto a rectangular agar plate using the parameters from the CSV file. The plates are 192 pixels by 128 pixels, so the image can be made up of up to 24,576 nanodroplets!

The plate is incubated 30˚C until the pigment-producing yeast cells grow to fill the agar plate, then plates are placed in a cold room to allow the colors to fully saturate.