An Engineered Variant of E. coli Nissle 1917 with Enhanced Transformation Efficiency and Robustness

The gut microbiome and its effects on human health have
generated
considerable scientific, veterinary, and medical interest in recent
years. Several gut bacterial species have emerged as potential chassis
organisms for the delivery of therapeutics in this milieu. Among these, E. coli Nissle 1917 (EcN), a nonpathogenic gut isolate
bacterium, is quickly gaining popularity. However, a bottleneck in
harnessing EcN’s potential has been its poor transformation
efficiency relative to other bacterial strains. In this study, we
present the use of adaptive laboratory evolution to increase EcN’s
transformation efficiency by subjecting the strain to repeated cycles
of electroporation and recovery. This new strain has been comprehensively
characterized in comparison to the wild-type EcN, including assessments
of growth under gut-mimicking duress conditions, permeability, motility,
hydrophobicity, and plasmid replication. Since EcN is known to compete
with pathogenic strains in the gut for iron, the competition dynamics
and iron consumption of the strain were also significant factors to
consider. Furthermore, we conducted genome sequencing and gene ontology
enrichment analysis to identify affected genes and pathways to probe
the potential mechanisms of the improved phenotype. Overall, the strain
shows improved transformation efficiency and robustness while preserving
its key biological functionality.