UC San Diego Team Builds a CRISPR Gene Drive That Spreads Through Bacteria and Strips Away Antibiotic Resistance
A second-generation Pro-Active Genetics system spreads via bacterial conjugation to disable resistance genes on plasmids, working even inside biofilms.
Overview
Researchers at the University of California San Diego have developed a CRISPR-based genetic system that can spread autonomously through bacterial populations and disable the genes that make them resistant to antibiotics. The tool, called pPro-MobV, represents a second-generation Pro-Active Genetics (Pro-AG) platform that borrows the gene-drive concept used against malaria-carrying mosquitoes and applies it to one of medicine’s most urgent crises: the rise of drug-resistant bacteria.
The work, published in the journal npj Antimicrobials and Resistance, was led by professors Ethan Bier and Justin Meyer of UC San Diego’s School of Biological Sciences, according to a UC San Diego press release.
How It Works
The pPro-MobV system packages two arabinose-inducible components—λRed recombination machinery and Cas9—alongside an sgRNA cassette that targets the bla ampicillin resistance gene carried on bacterial plasmids. Conjugation machinery derived from the IncP RK2 system allows the cassette to hitch a ride through the natural mating tunnels that bacteria form during conjugal transfer, as Phys.org reported. Once inside a recipient cell, the CRISPR components cut the resistance gene and a homology-based deletion mechanism excises the intervening sequence, restoring the bacterium’s vulnerability to antibiotics.
The team demonstrated the system using Escherichia coli Epi300 as the donor strain and E. coli MG1655 as the recipient, confirming that conjugal transfer of pPro-MobV efficiently inactivates the bla gene in a liquid conjugation assay.
Works Inside Biofilms
One of the most significant findings is that pPro-MobV functions within bacterial biofilms—dense communities of microorganisms that form protective layers on surfaces and are notoriously resistant to conventional antibiotic treatment. According to ScienceDaily, the system was shown to spread its disabling cassette even through these fortified microbial structures, a capability that could prove critical in clinical settings where biofilm-associated infections are among the hardest to treat.
The researchers also demonstrated that bacteriophages—viruses that naturally prey on bacteria—can carry and deliver pPro-MobV components, opening the door to dual-action therapeutic strategies that combine phage therapy with genetic disarmament.
What We Don’t Know
The published experiments were conducted in E. coli under laboratory conditions. Whether pPro-MobV can effectively spread through the diverse, multi-species bacterial communities found in real-world environments such as hospital wards, wastewater treatment plants, or agricultural operations remains to be demonstrated. The transition from a controlled conjugation assay to complex ecosystems introduces variables—including competition from native bacteria, varying environmental conditions, and the sheer genetic diversity of resistance mechanisms—that could limit the system’s reach.
It also remains unclear how regulators would evaluate the deliberate environmental release of a gene-drive system in bacteria, a step that would raise biosafety questions distinct from those surrounding insect gene drives.
Built-In Safeguards
The team incorporated a safety mechanism: the homology-based deletion process that disables resistance genes can also be used to remove the inserted genetic cassette itself, according to the UC San Diego announcement. This reversibility is designed to address concerns about uncontrolled spread in the environment.
Why It Matters
Antibiotic-resistant infections currently kill an estimated 1.27 million people worldwide each year, a toll projected to exceed 10 million annual deaths by 2050 if current trends continue, according to ScienceDaily. Roughly half of all antibiotic resistance is believed to originate from environmental sources rather than clinical overuse.
“With pPro-MobV we have brought gene-drive thinking from insects to bacteria” as a population engineering tool, Bier said in the UC San Diego announcement, adding that deploying just a few cells could neutralize resistance across much larger populations.
Meyer described the approach as “one of the few ways that I’m aware of that can actively reverse the spread of antibiotic-resistant genes, rather than just slowing” their progression, as reported by Phys.org.
The research was funded by the Tata Institutes for Genetics and Society at UC San Diego, the National Institutes of Health, and the Howard Hughes Medical Institute’s Emerging Pathogen Initiative. Bier is a co-founder of Agragene, a startup company, which the authors disclosed as a competing interest.