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PI-Submitted Research Highlights for
Subsurface Biogeochemical Research Program

Major New Microbial Groups Expand Diversity and Understanding of the Tree of Life

Jillian Banfield

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May 29, 2019

New evolutionary patterns and diversity revealed from genome-resolved metagenomics.

The Science
Understanding of microbial diversity has been dramatically expanded through analysis of genomes from groups of organisms previously inaccessible to laboratory-based identification and characterization.  

The Impact
Analysis of genomes from little-explored subsurface environments has uncovered new evolutionary patterns, including a group that may be ancestral to Eukaryotes, humanity’s own branch of life.  Also evident are two major radiations of microorganisms that appear to live primarily via symbiosis with other bacteria and archaea.  These organisms have ecosystem importance via impacts on their hosts, geochemical cycling, and potentially play roles in agriculture and human health.

Summary
The tree of life is arguably the most important organizing principle in biology and perhaps the most widely understood depiction of the evolutionary process. It explains how humanity is related to other organisms and where we may have come from. The tree has undergone some tremendous revolutions since the first version was sketched by Charles Darwin. A major innovation was the construction of phylogenetic trees using DNA sequence information, work that enabled the definition of the three domains of life: Bacteria, Archaea, and Eukaryotes. More recently, the three-domain topology has been questioned, and eukaryotes potentially relocated into the archaeal domain. Beyond this, and as described here, cultivation-independent genomic methods that access sequences from organisms that resist study in the laboratory have added many new lineages to the tree. Their inclusion clarifies the minority of life’s diversity represented by macroscopic, multi-celled organisms and underscores that humanity’s place in biology is dwarfed by bacteria and archaea.

BER PM Contact
Paul Bayer
Department of Energy
paul.bayer@science.doe.gov

Contact
Jillian Banfield
Lawrence Berkeley National Laboratory
jbanfield@lbl.gov

Funding
Support was provided by grants from the Lawrence Berkeley National Laboratory’s Genomes-to-Watershed Scientific Focus Area. The  Office of Biological and Environmental Research within the U.S. Department of Energy (DOE) Office of Science funded the work under contract DE-AC02-05CH11231 and the DOE carbon cycling program DOE-SC10010566, the Innovative Genomics Institute at Berkeley, and the Chan Zuckerberg Biohub.

Publication
C. J. Castelle and J. F. Banfield, “Major New Microbial Groups Expand Diversity and Alter our Understanding of the Tree of Life.” Cell 172(6), 1181–97 (2018). [DOI:10.1016/j.cell.2018.02.016].

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