Bacillus Citrus
Designing a Synthetic Microbe That Navigates by Magnetism and Defends Itself With Genes Borrowed From Five Organisms
Context
What the system looked like before.
The project designed a synthetic microbe, Bacillus citrus, engineered to survive a specific transition: starting in a low-osmolarity "nursery" environment, then moving into a shared microbial community vessel with much higher osmolarity and a complex mix of other microbes. To survive and function there, the microbe needed to metabolize oxalate for energy and acetate for biomass, communicate with neighboring microbes via quorum sensing, navigate using magnetic field cues, and defend itself against predatory species already present in the community.
Question
Can a single synthetic organism be engineered to survive osmotic shock, metabolize an unconventional energy source, communicate with its community, navigate environmentally, and defend itself — all at once, using genetic parts borrowed from unrelated organisms?
Approach & rationale
The design combined genetic parts from multiple organisms into one proposed genome: quorum-sensing signaling (LuxI/LuxR-family genes, originally from Aliivibrio fischeri, with a receptor from Ruegeria pomeroyi) to detect cell density; magnetosome-formation genes from magnetotactic bacteria such as Magnetospirillum magneticum to build organelles that align the cell with Earth's magnetic field; flagellar and chemotaxis genes for motility and gradient-sensing; oxalate/acetate metabolic pathways feeding an electron transport chain for energy; osmolyte and potassium-transport systems for surviving the nursery-to-community osmotic shock; and secretion systems for defense against predators.
Methodology & iteration
Including the paths that did not hold.
The gene-part registry behind the design catalogues roughly 128 gene/part entries across categories — signal detection, magnetosome formation, flagellar assembly, chemotaxis, outer-membrane structure, peptidoglycan synthesis, ribosomal machinery — each tagged with its source organism (E. coli, Aliivibrio fischeri, Ruegeria pomeroyi, Magnetospirillum magneticum, plus Homo sapiens and Citrus sinensis for a limonene-synthesis pathway) and its proposed genomic location.
In short
The deliverable was the design itself — a complete proposed genetic circuit, backed by a gene-part registry, presented as a poster.
Results
Numbers first, not buried in prose.
The deliverable was the design itself — a complete proposed genetic circuit, backed by a gene-part registry, presented as a poster. No wet-lab implementation or experimental validation was part of this project.
Significance
Where this went.
Presented as a poster, "Exploring Bacillus Citrus: Characteristics & Roles" — Epsilon team, University of Tennessee, Knoxville.
Reflection
This was a team project — the design above covers the whole system as presented. Which parts I personally led is still being added here.