New light-sensing ability discovered in disease-causing bacteria

The bacteria that cause brucellosis can sense light and use the information to regulate their virulence, according to a study in the August 24 issue of the journal Science. The discovery comes after 120 years of research into the disease, which causes abortions in livestock and fevers in humans. Researchers found that two other bacteria, including a species that attacks plants, sense light using the same type of protein structure, and at least 94 more species possess the code for it in their DNA.

"These bacteria have been very well studied for years, and no one knew they could sense light," said lead author Trevor Swartz, who initiated the study as a research scientist at the University of California, Santa Cruz. "Now it seems like it's a common thing rather than being an anomaly."

The ubiquity of the structure suggests that light may play a much more important role in bacterial life than has previously been recognized. And because the recurrent structure can be paired with a variety of signaling proteins, it gives organisms immense versatility in the ways they use light, Swartz said.

"We have bumped into an entirely new family of light receptors in nature," said coauthor Roberto Bogomolni, professor of chemistry and biochemistry at UCSC.

The receptor molecule contains a light-sensing region known as an LOV domain because it resembles similar units in other proteins that sense light, oxygen, or voltage, said coauthor and longtime collaborator Winslow Briggs, of the Carnegie Institution of Washington. The structure crops up in a variety of proteins, where it lends its light-sensing ability to the whole molecule. The light-sensing structure is very different from either the light-harvesting molecules of photosynthesis or the light-gathering pigments in our own eyes.

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