( survive S. ruber must maintain a high ...)A salty tale: New bacterial genome sequenced from ancient salterns

Analyzing the bacterium's genome, researchers found that S. ruber's proteins are typically rich in acidic amino acids and relatively poor in hydrophobic (water-repellent) amino acids, making them soluble and highly stable at such salt concentrations. Researchers recognized this biochemical adaptation: it's the same one used by archaea also living in the salterns.

That wasn't the only similarity. Scientists also found two types of rhodopsin genes: one variety typical for bacteria, and another previously recognized in archaea. A photosynthetic protein, rhodopsin works as a proton pump, capturing light energy and using it to move protons across the membrane and out of the cell. In doing so, the protein maintains a balance of ions inside and outside the cell.

"It's very unusual to find the two different types of rhodopsin in the same organism," Mongodin says. "S. ruber may have independently evolved one type of rhodopsin and acquired the other through lateral gene transfer from the archaeal species also living in the salterns." This study is the first to document bacteria adopting the archaeal-type rhodopsin. The two systems may work at different wavelengths, expanding S. ruber's ability to thrive in this environment. Alternatively, Mongodin says, the double system may be redundant, a kind of biological back-up.

Because S. ruber grows in high salt, its enzymes are strikingly stable. And that means the bacterium may hold promise for industrial applications. Meanwhile, TIGR's collaborators are pursuing studies of Spain's salterns, testing the ponds to find out what other microbes call the briny waters home. "How much diversity is there?" Mongodin asks. "We'll all be interested to learn."