The biofunctionalization of advanced materials (using antibodies, oligonucleotides, etc) is well-established, particularly to equip nanostructures and microfabricated devices for biosensing applications. It follows that the inclusion of entire microorganisms to similar abiotic platforms could offer next-generation materials with genetically programmable behaviors. This work scopes microbial engineering approaches for constructing such bio-composites, whereby controlled cell assembly with spatial precision is needed along with responsive gene expression for operational tasks. Inspired by natural adherence mechanisms of E. coli to host tissues, the AIDA-I autotransporter and type 1 fimbriae were identified as candidates to facilitate interfacing with abiotic materials. These membrane proteins were repurposed by incorporating alternative residues that promoted various interaction pairings: streptavidin-biotin, adhesin-ligand, and peptides for inorganics-binding. Such sequence modifications resulted in cell binding either directly to patterned inorganics (eg gold) or instead to biomolecules immobilized on the material’s surface. Specifically, the fimbrial tip adhesin accommodated point mutations that distinctly tuned affinity for its natural ligand as well as foreign peptides that substituted entirely new binding functionality. Further, its shear-dependent conformational switch enabled flow-based control of cell binding events. Alternatively, the autotransporter adhesin allowed the surface display of large recombinant structures- in this case, an affinity peptide-tagged fluorescent protein. This fused entity was used to bind functionalized magnetic nanoparticles to cells; further, its expression was dependent on a threshold in signaling exchanges by neighboring cells. The resulting biohybrid system held the capacity to respond to intercellular communication coupled with magnetically-activated assembly of the responder cells. Overall, engineered cell binding, with specificity designated by the refactoring of membrane protein architectures, allowed for broader capabilities: delineated patterning of populations, controlled onset of assembly by external stimuli, and genetically-defined supplemental cellular functions. These outcomes may benefit in situ seeding of interactive consortia. Additionally, tailoring bacteria for interfacing with abiotic materials could yield advancements in “living” biohybrid systems.

Alteration of bacterial surface protein architectures for guided assembly of cell populations

253rd National Meeting (2017)

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