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Scientists commonly use electricity to increase the permeability of bacterial
cell membranes, making it easier to insert DNA. Now Sandrine Demanèche’s
team at the University of Lyon has provided the first evidence that nature may
have been wise to this trick all along.

The researchers seeded soil samples with the E. coli bacterium, as
well as fragments of DNA containing genes for antibiotic resistance. They zapped
the soil with a simulated lightning strike, and found that many of the bacteria
had acquired the resistance genes.

Bacteria are already known to take up and use foreign DNA released into the
environment when other organisms die. Scientists knew this “horizontal gene
transfer” occurs naturally in soil, but thought it was relatively rare. However,
recent genomic research indicates that this gene take-up is widespread and has
played a major role in the evolution of the bacterial genome.

“This result might help explain the discrepancy between the very low observed
rates of gene transfer and the apparently wide distribution of DNA sequences
among bacteria,” says team member Timothy Vogel.

Lightning may seem relatively rare, but there are about a hundred flashes a
second around the planet. Ground strikes almost always create currents in the
surrounding soil similar to those from the simulated bolts, Vogel says.