Science1 publisher2 min readPublished
Starving E. coli swap DNA through phages over 100 times more often than they mutate
ISTA biologists report that starving E. coli use phages and CRISPR-Cas to swap and absorb DNA more than 100 times as often as spontaneous mutation. The team describes it as a primitive form of sexual reproduction that may speed how populations adapt.
The Scientist · Science desk
What happened
- The DNA exchange shows up only as the cells approach starvation, when resources are running out.
- On its own, the virus-borne route called transduction cannot run often, because a growing phage population kills off the susceptible cells it needs to infect.
- CRISPR-Cas, better known as a gene-editing tool, protects the recipient cells by targeting the phage genome, so the exchange can continue.
- The results appear in the journal Molecular Biology and Evolution.
Compiled by The ScientistSomething wrong?How this is made
Why it matters
- constraint Taking up free DNA the classical way, natural competence, works in only a minority of species, so a route running on phages and CRISPR-Cas sidesteps that limit.
- precedent The result strengthens a view, building since the 1990s, that bacteria run a primitive sexual process alongside ordinary cell division.
- capability Useful mutations are rare and tend to arise in separate cells, so exchange that pools them into one genome lets a population adapt faster than mutation can within a single lineage.
The 100-fold figure compares two rates: how often a starving cell takes up foreign DNA and keeps it, against how often a cell picks up a spontaneous mutation [3]. The work comes from Pavel Payne, a postdoc, and Calin Guet, a professor, both at ISTA [4]. Their account lays out the mechanism and the evolutionary case. It does not describe the assay, the strains, or the controls behind that ratio.
Transduction, the virus-borne transfer this depends on, was found a few years after conjugation in the 1940s [8][9]. The protection a defended cell gains does not stay with that cell. In his doctoral work, Payne found that bacterial immunity can produce herd immunity across a population [12]. "Herd immunity not only protects the bacteria that directly carry the immune system, but also those that don't," Payne said [13].
E. coli is a gut organism [1]. The account does not show that the exchange runs at the same rate in a living gut, where the mix of phages, nutrients and rival microbes differs from a stressed lab culture. The clearer result is about CRISPR-Cas, usually cast only as antiviral defense or the basis for gene editing. "It turns out that bacteria use these viruses to shuttle DNA between themselves. Furthermore, recipient cells can incorporate this DNA into their own genomes and transmit it vertically to their offspring, which is de facto sex," Guet said [5].
What to watch
- Whether the full paper's assay and controls support the claim of exchange over 100 times as common as mutation.
- Whether the same phage-and-CRISPR route moves functional traits in a living gut, not just DNA in a stressed culture.
- Whether bacterial species that lack natural competence use this route the same way.