The Tree of Life has three great branches: the eukaryotes,
including all plants, animals, fungi, and single-celled
creatures like malaria parasites and amoebae. There are the
prokaryotes, or bacteria. And there are the Archaea, a group of
single-celled organisms divergent from both the other groups.
Life on this planet is overwhelmingly single-celled. A cup of
sea water or soil teems with thousands of species, many yet to
be discovered. But for the most part, microbiologists only know
about those organisms that they can grow in the lab. Now
Jonathan Eisen at the UC Davis Genome Center and colleagues may
have discovered signs of a fourth, novel branch of life — or
they may have found a lot of weird viruses. Eisen says that he
really doesn’t know the answer, but he’s putting the data out
there (a paper appeared last week in the journal Public Library
of Science (PLoS) One). On his blog, Eisen tells the story
behind this research, which began some years ago when he was
working at The Institute for Genome Researc