A recent survey of microbial life found that the oceans are teeming with 10 to 100 times more unique species than scientists expected. The vast majority are previously unknown organisms that exist in low numbers but are thought to be vital to the marine environment. Using a new DNA sequencing tool that requires only a small amount of genetic material to identify an organism, an international team found more than 20,000 different kinds of bacteria in a single liter of seawater. Above, a small sample includes both well-known microbes such as Chromatium (large pink ovoid) and organisms that have not been previously identified (long dark filaments). Microbiologists have only formally described some 5,000 microbial species to date, but based on these new results, study authors estimate that there could be five to 10 million different kinds of bacteria in the ocean. The results are detailed in the July 31 online edition of the Proceedings of the National Academy of Sciences.