"Secreting Spider Silk in Salmonella" - Chris Voigt

Let's engineer a "super" salmonella that can construct and extrude silk filaments from its membrane. Spider silks have a wide variety of desirable materials properties. Dragline silk is equal strength of kevlar, but 10 times more elastic. Silks are amino acid biopolymers with elastic and crystalline elements, and thread can be spun simply from a solution of silk monomers.

Will need a complicated secretion tran-membrane protein, and the silk monomers will need an N-terminal secretion signal to direct them to the secretion "needle." Oh, and we'll also need a complicated regulatory network to turn things on in the correct order (i.e. only start producing the monomers after successful construction of the complicated secretion needle.

Salmonella encodes just such a needle that it uses to inject proteins into a host cell that induces it to endocytose the entire salmonella bacterium. The genes and control network for this needle are encoded in a so-called "pathogenicity island." The dymanics of this control network can be teased out by constructing plasmids with one of the promoters and a GFP gene, and then inducing the transformed cells to activate the pathogenicity island.

As of friday, an engineered strain of salmonella was producing a couple mg/l of silk monomers.