The newly discovered genes include those that help microbes use the sun's energy in new ways, help them use nitrogen and protect them from ultraviolet light, the scientists reported.
The Rockville, Md.-based team published its findings in the March issue of the Public Library of Science Journal PLoS Biology.
Study leader J. Craig Venter, who chairs a nonprofit gene research center, said the team's discoveries were just as plentiful at the end of the trip as at the start, suggesting much more can be learned about the planet's biodiversity.
"As amazing as this inventory is, it's only scratching the surface of what's really there," he told the Washington Post.
The researchers traveled on a 95-foot sloop from Halifax, Nova Scotia, to the Galapagos Islands. Every 230 miles, they pumped seawater through filters and analyzed 7.7 million DNA sequences, Venter told Bloomberg news.
They identified about 1,700 protein families that don't match previously known proteins.
The findings built on Venter's 2003 test voyage to the Sargasso Sea, considered an especially lifeless body of water. That trip yielded 1 million genes new to science, the Washington Post reported.
The data are posted on the Internet, which pleases scientists and governments but concerns some countries hoping to profit from the genetic discoveries in their waters.