A team, including DNA pioneer Craig Venter, says it may have discovered an entirely new domain of life.
]Most of us would regard it as a pretty reasonable achievement to discover a new species. But while there's roughly 100 million species on the planet, there have so far been thought to be only three domains of life. These are bacteria; single-celled archaea; and eukaryotes - which includes everything else, including us.
But a team including Craig Venter, who helped crack the human genetic code, now says it's discovered a fourth domain, through a detailed study of marine DNA. The team built evolutionary trees using the Venter Global Ocean Sampling data set and then looked for groups that were new.
They found a unique sequence that, they say, may just have originated from a previously undocumented form of life.
"We found some very phylogenetically novel forms of phylogenetic marker genes in metagenomic data. We do not have a conclusive explanation for the origin of these sequences," says evolutionary biologist Jonathan A Eisen of UC Davis.
But, he says, it's important not to overstate the findings. "Personally, I think it is most likely that these novel sequences are from weird viruses," he says.
"But as far as we can tell, they truly could be from a fourth major branch of cellular organisms; and thus, even though we did not have the story completely pinned down, we decided to finally write up the paper to get other people to think about this issue."
The paper, "Stalking the Fourth Domain in Metagenomic Data: Searching for, Discovering, and Interpreting Novel, Deep Branches in Marker Gene Phylogenetic Trees", is available here.