Synthetic Riboswitches Turn On Bacterial Genes

Scientists show that synthetic riboswitches can control gene expression in a wide variety of bacteria, including some organisms in which such control has been difficult. The research is published in the December 2010 issue of the journal Applied and Environmental Microbiology.

Bacteria regulate their metabolism using riboswitches, sequences of RNA that alter gene expression when they bind a small-molecule metabolite. In earlier work, Justin P. Gallivan's laboratory at Emory University in Atlanta created synthetic riboswitches, which the researchers can use to turn specific genes on or off, to control what the cell does.

In the current study Gallivan shows that can control gene expression in a wide variety of bacteria. More importantly, they have created riboswitches that function in certain pathogens, including Streptococcus pyogenes, the microbe that causes strep throat. That research should lead to a better understand the mechanisms of pathogenicity in these organisms, says Gallivan.

Traditionally, researchers investigate gene function by creating "knock-outs," organisms in which the gene of interest has been removed. The problem with that approach: removing an essential gene kills the cell, says Gallivan. But using riboswitches, the researchers could turn an essential gene off only briefly, to determine its function without killing the cell.

Another potential application of riboswitches is to program bacteria to perform complex tasks, says Gallivan. For example, riboswitches can be used to control bacterial movement. "By developing a riboswitch that responds to the herbicide, atrazine, we reprogrammed cells to follow atrazine," he says. "By then adding a gene that encodes an atrazine-catabolizing enzyme, we created cells that seek and destroy atrazine." Such an organism could be developed for cleaning up pollution."

Reference: S. Topp, C.M.K. Reynoso, J.C. Seeliger, I.S. Goldlust, S.K. Desai, D. Murat, A.W. Puri, A. Komeili, C.R. Bertozzi, J.R. Scott, and J.P. Gallivan, 2010. Appl. Environ. Microbiol. 76:7881-7884.