Establishment of Bacteroides as a synthetic biology chassis
Metabolism, Biochemistry and Genetics of Microorganisms
Final Report Abstract
During my DFG research fellowship, I focused on establishing the prevalent gut commensal Bacteroides thetaiotaomicron (B. theta) as a synthetic biology tool. Specifically, my goal was to harness B. theta for the expression and targeted delivery of recombinant peptides and proteins. Already when I started my project, it became apparent that other groups were close to publishing results which I had set as goals in my DFG proposal, i.e. the design of transcriptional regulators for controllable expression in B. theta. Therefore, I decided to work with these available tools for the production and delivery of various peptides and proteins in B. theta. In addition, I designed an all-synthetic plasmid for stable chromosomal integration of different DNA building blocks. For expression and targeted release of small peptides, I engineered a proteinaceous capsule in B. theta and tested functionality of the system with the Linaclotide and GLP-1. While Linaclotide was expressed but not folded correctly due to the lack of disulfide bonds, GLP-1 was functionally released through the shuttle system in vitro. This demonstrates proof-of-concept for usage of a proteinaceous capsule for secretion of peptides. In addition, I also developed a controllable lysis system for release of larger proteins from B. theta. Due to lack of collaboration partners at USCF for testing of the above-mentioned systems in vivo, I had to put both projects on the back burner. After my transition to ETH, an exciting opportunity to work on vaccination-induced IgA responses opened up in collaboration with Emma Slack (a former member of the Hardt lab). Moor et al. had shown that IgA protects the intestine by enchaining growing bacteria. Vaccine-induced IgA was effective against growing pathogens such as Salmonella by formation of clumps and crosslinkage of daughter cells. However, it has been unclear whether also commensal bacteria could induce a similar IgA response in vivo. With the tools that I had developed at UCSF at hand, I showed that enchained growth can not only be induced in pathogenic bacteria, but also the abundant commensal B. theta. This also builds the foundation towards controlling complex communities in the gut through oral vaccinations.
