(Trees from Darwin (1837), Haeckel (1866), and Woese (1990))
We’ve come quite a long way since Darwin sketched out his tree in 1837 connecting, with branch tips representing animals and microbes currently in existence and branches and trunks their ancestors. The most recent tree of life was revealed yesterday in Nature Microbiology, the latest and most extensive view of biodiversity on the planet.
The study released by a group of researchers led by Jillian Banfield, is the most up-to-date view of genetic diversity to date. This tree was made possible due to relatively recent advances in sequencing, which have illuminated the vast biodiversity of the uncultivated microbes that surround us. Thanks to all this technology, we can paint a better picture of microbial communities, which apparently include a large group of uncultivated organisms. Banfield is a leader in the field of metagenomics, publishing landmark studies highlighting the diversity present at toxic acid mine drainage sites.
In the paper by Hug and colleagues, they put 1,011 unpublished genomes together with previously known representatives of diversity for a grand total of 3,083 organisms included in the tree. These previously unaccounted for genomes were gathered from environments ranging from a grassland meadow, to a geyser and even the mouths of two of Flipper’s cousins. The tree was constructed using 16 protein coding genes that form part of the ribosome, and clearly demonstrates that although all of us higher eukaryotes take up a bunch of space, and are the most easily observed organisms on the planet, we are far from contributing much to global biodiversity. The uncultivated majority continues to elude us: from hot springs to dolphin mouths, there’s a ton of stuff that we just don’t know a lot about.
(brand spanking new tree o’ life from Hug et al., Nature Microbiology)
This new phylogeny is just the beginning of chipping away at a better understanding of microbial diversity and unraveling the biosynthetic potential and role in the environment of the vast group of microbes that we just can’t seem to cultivate (yet anyway). It’s no surprise that a huge chunk of the bacteria in the “candidate phyla radiation (CPR)” make up an extensive branch of the tree, and are bugs associated with symbiotic lifestyles.
Since Darwin’s first tree attempt, to one of the most well known trees published by Carl Woese (representing the three currently recognized domains of life) this latest version expands the branches. The tree is growing and it will be pretty dang exciting to see what future advances in sequencing and genome analysis will add to our view of biodiversity on Earth.
Laura A. Hug, Brett J. Baker, Karthik Anantharaman, Christopher T. Brown, Alexander J. Probst, Cindy J. Castelle, Cristina N. Butterfield, Alex W. Hernsdorf, Yuki Amano, Kotaro Ise, Yohey Suzuki, Natasha Dudek, David A. Relman, Kari M. Finstad, Ronald Amundson, Brian C. Thomas, Jillian F. Banfield. A new view of the tree of life. Nature Microbiology (2016) DOI: 10.1038/nmicrobiol.2016.48
Woese, Carl R., Otto Kandler, and Mark L. Wheelis. Towards a natural system of organisms: proposal for the domains Archaea, Bacteria, and Eucarya. Proceedings of the National Academy of Sciences 87.12 (1990): 4576-4579. DOI: 10.1073/pnas.87.12.4576