Biology’s ‘dark matter’ hints at fourth domain of life
This piece is three years old now but I seem to have missed all this.
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To probe life’s dark matter, Eisen, Craig Venter of the J. Craig Venter Institute in Rockville, Maryland, and their colleagues have resorted to a relatively new technique called metagenomics. This can “sequence the crap out of any DNA samples”, whether they are collected from the environment or come from lab cultures, says Eisen.
When Eisen and Venter used the technique on samples collected from the Global Ocean Sampling Expedition, they found that some sequences belonging to two superfamilies of genes – recA and rpoB – were unlike any seen before.
“The question is, what are they from?” says Eisen. Because the team has no idea what organism the genes belong to, the question remains unanswered. There are two possibilities, he says. “They could represent an unusual virus, which is interesting enough. More interestingly still, they could represent a totally new branch in the tree of life.”
The exciting but controversial idea has met with mixed reactions. “It’s a very good piece of careful work,” says Eugene Koonin at the National Center for Biotechnology Information in Bethesda, Maryland.
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