Team:Harvard/Description
Project Description
Overview
Chemical synthesis is the most commonly used method of producing industrially relevant molecules, yet this practice is often accompanied by various environmental hazards. Biological synthesis, on the other hand, does not produce any toxic byproducts, nor does it require expensive starting materials. In the long run, it is a better manufacturing solution in many respects.
One strategy for biological synthesis is to adapt pre-existing systems already in nature. For instance, E. coli produces proteinaceous components in its biofilm called curli fibers. These fibers self-polymerize outside of the cell, forming a macroscopic agglomeration of material when isolated in sufficient bulk. The Joshi lab has already demonstrated how various functional peptide domains can be added to the self-polymerizing units of curli, so the polymers can form the basis of a variety of functional materials.
Our project focuses on optimizing curli production on two fronts as a first step to developing the curli system into a robust platform for producing materials at industrially relevant yields. First, we alter ribosome binding site strengths associated with various proteins involved in the curli pathway -- chaperones, transporters, and self-polymerizing units -- to optimize the stoichiometric ratios of these molecules in the cell. The alterations are informed by a model of curli production and export that determines the optimum ratio of pathway components to maximize the production of our desired product, extracellular curli fibers, and minimize the aggregation of unwanted byproducts within the cell. This ensures that each cell becomes a more efficient curli export machine. The second component of the project aims to maximize cell densities within culture media through the development of a bioreactor that maintains higher dissolved oxygen concentrations than standard shaker flasks. Eliminating the limiting factor of insufficient oxygenation allows bacterial cells produce more curli per unit of feedstock. This aspect of the project aims to optimize the conditions for protein-producing cell cultures. Our work along these two lines will inform the development of the curli system as a feasible biosynthetic platform for producing scalable and programmable materials.
Curli System
Goyal, Parveen, et al. (2014)
CsgA: Secreted polymer
CsgG: Extracellular matrix secretion pore
References
- Source: Goyal, Parveen, et al. "Structural and mechanistic insights into the bacterial amyloid secretion channel CsgG." Nature 516.7530 (2014): 250-253.
