Team:MIT phage


hairy cells and polymerizing phage - introduction

Living Material--Bacteriophage Polymer
M13 bacteriophage, a filamentous virus of E. coli, has been used as the starting component for polymers and other materials. To make these phage materials, one must purify large amounts of the virus, and then cross-link them with chemicals such as glutaraldehyde. Although once part of a living system, these materials are static--once made, they cannot be changed.

Figure 1: M13 polymer This polymer was created using external cross-linking, and is an example of a "static" material. In contrast, we want our material to be "dynamic" and biologically encoded--no external linkers required.

Willis, et al. 2007

We set out with the goal of constructing a system in which living cells would be programmed with a set of instructions, and given a stimulus, would be able to form material in a pattern. Because it is truly living, this system would have the potential to change and adapt, given more sophisticated programming.

For the bacterial path of our "living materials" project, we had to find a way of forming material without destroying the cells that created it. Luckily, M13 bacteriophage is non-lytic, which means that cells infected with M13 secrete phage continuously, without lysing.

The phage material that we set out to create is composed of polyphage strands, produced by cells that carry an M13 plasmid that lacks the gene necessary for termination of the phage particle. These strands cross-link with one another via the coiled-coil interactions of proteins displayed on the phage coat.

Figure 2: Electron micrograph of E. coli with polyphage hairs
Our goal is to get these hairs to cross-link via coiled coil interactions. (Despite what it may look like, these are not cross-linking.)
Rakonjac and Model, 1998