Boldly Illuminating Biology's 'Dark Matter'

Is space really the final frontier, or are the greatest mysteries closer to home? In cosmology, dark matter is said to account for the majority of mass in the universe, however its presence is inferred by indirect effects rather than detected through telescopes.

The biological equivalent is "microbial dark matter," that pervasive yet practically invisible infrastructure of life on the planet, which can have profound influences on the most significant environmental processes from plant growth and health, to nutrient cycles in terrestrial and marine environments, the global carbon cycle, and possibly even climate processes.

By employing next generation DNA sequencing of genomes isolated from single cells, great strides are being made in the monumental task of systematically bringing to light and filling in uncharted branches in the bacterial and archaeal tree of life. In an international collaboration led by the U.S. Department of Energy Joint Genome Institute (DOE JGI), the most recent findings from exploring microbial dark matter were published online July 14, 2013 in the journal Nature.

This microbial dark matter campaign targeted uncultivated microbial cells from nine diverse habitats: Sakinaw Lake in British Columbia; the Etoliko Lagoon of western Greece; a sludge reactor in Mexico; the Gulf of Maine; off the north coast of Oahu, Hawaii, the Tropical Gyre in the south Atlantic; the East Pacific Rise; the Homestake Mine in South Dakota; and the Great Boiling Spring in Nevada. From these samples, the team laser-sorted 9,000 cells, from which they were able to reassemble and identify 201 distinct genomes, which then could be aligned to 28 major previously uncharted branches of the tree of life.