Cell sex - how bacteria get it on

Scientists have long known that bacteria practice a form of sex through conjugation, or direct cell-to-cell contact, but no one has actually caught them at it, until now.

A French research team has captured bacterial conjugation on film, showing in real time how E. coli swaps DNA through horizontal gene transfer.

Conjugation allows bacteria to acquire genes for antibiotic resistance, amongst other benefits.

In bacteria like E. coli, contact between cells is mediated by a tubular organelle called the F pilus, which extrudes from the surface of the donor cell, the researchers, writing in the March 14 issue of Science, say.

Some believe the F pilus brings the mating cells together and DNA is then transferred through a pore in the membrane. Others believe that DNA can be transferred even if the cells don't come into direct contact.

The French team, led by Ana Babic from the Institut Pasteur in Paris, has shown that the F pilus does indeed allow gene transfer at a distance and have recorded the process at a distance of up to 12 micrometres.

They have developed a technique to distinguish the transferred donor DNA from both donor and recipient DNA and to visualise the transfer and recombination by fluorescence microscopy in real time.

They say the technique can be used to monitor horizontal gene transfer by following the fate of the swapped DNA.