THE bacteria in our guts routinely indulge in scenes that would make the director of a porn movie blush 鈥� frenetic orgies where clusters of individuals get together to share DNA. But now it turns out that the promiscuous creatures are even kinkier than anyone realised.
Virginia Waters, a geneticist at the University of California in San Diego, has found that the common gut bug Escherichia coli will even do the deed with mammalian cells. She thinks it might be possible to harness such bacterial bestiality for a variety of purposes 鈥� as an alternative to viruses in gene therapy, for example.
鈥淵ou could use any bacteria that grow anywhere on the human body,鈥� she says. 鈥淚f you chose normal flora, the therapy could potentially go on indefinitely.鈥�
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When bacteria 鈥渃onjugate鈥� with each another, one cell passes a circular bit of DNA called a plasmid to the other. To see if E. coli can pass these plasmids on to mammalian cells, Waters added several marker genes to E. coli plasmids and left the bugs in a dish with hamster ovary cells overnight. Two days later, she found that many of the hamster cells were expressing the marker genes.
Her study is one of only a handful to show that bacteria can conjugate with more complex cells. In the early 1980s, researchers found that the soil bacterium Agrobacterium tumefaciens can transfer genes to plants 鈥� the finding that opened the door to genetically modified crops. Earlier this year, a team at the State University of New York at Stony Brook showed that Agrobacterium can conjugate with cultured human cells.
But unlike Agrobacterium, E. coli is adapted to conditions inside the human body. This makes them a better candidate for therapies in which bacteria are given directly to patients.
Current gene therapy techniques rely mainly on viruses, which can accommodate only a limited amount of DNA. 鈥淲ith [bacterial] conjugation there鈥檚 no upper limit to the DNA that can be transferred, and that鈥檚 potentially very nice,鈥� says Peter Christie, a bacterial geneticist at the University of Texas-Houston Medical School.