Spatiotemporal Dynamics of Synthetic Microbial Consortia
Alnahhas, Razan Nasser
Bennett, Matthew R
Doctor of Philosophy
Synthetic biology traditionally entails the engineering of microbial organisms for a variety of applications such as producing desired products or studying components of gene circuits in nature. For example, synthetic gene oscillators provide information on the function of circadian clocks, and genetic toggle switches are involved in cellular memory networks. As synthetic biology projects become more complex, switching to multiple strains working together becomes advantageous. Multiple engineered strains working together is referred to as synthetic microbial consortia. The first advantage of synthetic microbial consortia is the lessening of the metabolic load on each strain by dividing up tasks. Secondly, splitting up processes makes optimizing one step within each strain a more straightforward task than optimizing several reactions within one strain. Engineered microbial consortia also allows synthetic biologists to study the dynamics of different intercellular and inter-strain interactions. In the first part of this project we establish how a microfluidic environment can affect stability of strains in a consortium. Fluctuations in strain ratios affect the productivity of the engineered circuit, and loss of a strain will break the circuit completely. We determined the ideal environmental factors to ensure for a stable population over time. We also measured signaling distances across communities to determine how close cells need to be in order to communicate or work together. Next, we engineered a consortium with a novel phenotype: gene expression patterns that depend on the ratio of strains within the consortium. This was done by expanding the traditional co-repressive toggle gene circuit to two strains. In our system, there are two engineered strains that each repress the expression of synthetic genes in the opposite strain. This results in a majority wins pattern of gene expression. In nature, bacteria can adjust gene expression based on the overall population size, but our engineered multicellular gene circuit adjusts gene expression based on the ratio of strains within the population. Overall in this work, we have determined ideal environments for synthetic microbial consortia and engineered a consortium with a novel phenotype.
Synthetic Biology; synthetic microbial consortia; microfluidics; ratiometric gene expression