Biophysical Society Thematic Meeting - October 25-30, 2015

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 d around 10 −15 M. First, we engineered E. 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.

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