Genomic Recoding Broadly Obstructs the Propagation of Horizontally Transferred Genetic Elements.
Level 5 - mechanism / opinion, no new human data
In vitro microbiological and genetic engineering laboratory experiment (Level 5 by CEBM bench-research rule).
PubMed 27426981 · doi:10.1016/j.cels.2016.06.009
What was done
Researchers tested the propagation of horizontally transferred genetic elements in an engineered Escherichia coli strain lacking all UAG stop codons and release factor 1 (RF1). They challenged the recoded host with multiple bacteriophages (λ, M13, P1, MS2) and conjugative plasmids (F, RK2). They also tested whether synthetic recoding of UAG to UAA in viral and plasmid genomes restored function, and assessed viral adaptation during serial propagation on mixed communities of wild-type and recoded cells.
What was found
The alternative genetic code conferred resistance to phages λ, M13, P1, and MS2 at titers up to 10(11) PFU/ml and impaired conjugative plasmid transfer (F and RK2) by up to 10(5)-fold. Recoding UAG codons to UAA in the phages and plasmids restored infectivity and conjugation. Propagating viruses on mixed communities of standard and recoded cells reduced viral titers, though viruses adapted to the alternative genetic code over time.
Why it matters
This demonstrates that genomic codon reassignment acts as a broad genetic firewall to shield synthetic biological systems from horizontal gene transfer and viral infection.
Limits
The study is restricted to in vitro laboratory bacterial models using a specific set of phages and plasmids. Furthermore, the observed evolutionary adaptation of phages in mixed populations indicates that single-codon recoding alone does not guarantee permanent barrier isolation.
Cited by
- supports Genomically recoding an organism by altering codons can confer broad viral resistance, which has been experimentally achieved in E. coli.