Biophysical Society Thematic Meeting

- 61 -

Polymers and Self Assembly: From Biology to Nanomaterials Poster Session I

38-POS

Board 38

Engineered Living Cells that Program Self-Assembly to Spawn Artificial Cells

Ruihua Zhang, Sung-Ho Paek, Keith C. Heyde,

Warren C. Ruder

Virginia Polytechnic Institute and State University, Blacksburg, VA, USA.

Synthetic biology has made significant strides in creating tools for programming intracellular

material assembly. We leveraged this control and harnessed the capacity of

E. coli

to produce

biotin to guide polymer self-assembly. Biotin plays an essential role in cell growth although

requirements are low (e.g., 1 ng/ml in

E. coli

). Biotin is also widely used in molecular assembly

because of its strong attraction to streptavidin, with a K

around 10

−15

M. First, we engineered

coli

with a synthetic gene circuit that increased biotin production 17-fold. Next, we leveraged

biotin's attraction to streptavidin in a competitive binding scheme to create a biotin sensor that is

both specific and sensitive in comparison to common biotin assay methods. We used the sensor’s

underlying biophysical processes to control the assembly of DNA polymers on streptavidin-

functionalized microbeads, using biotin to tune this self-assembly. We then encapsulated these

beads - along with a cell-free expression system consisting of ribosomes, ATP, and RNA

polymerase - within hydrofluorocarbon microdroplets. The entire construct functioned as an

artificial cell, whereby the addition of biotin to the system repressed synthetic gene expression.

As a result, we used biotin to control cell-free synthetic gene circuits within artificial cells. This

work shows the utility of linking self-assembling polymer systems with synthetic biology. We

believe this system provides insight into the origins of life as this work shows that living cells

can express extracellular molecular signals - in this case, biotin - to control the assembly and

function of minimal cells. In the future, this work could impact fields ranging from biophysics to

synthetic biology.