An unknown group of archaea was discovered in hot springs and hydrothermal vents on Earth. In contrast to the other, smaller micro-size microbes that live deep in the sediment and feed on decaying plant matter, these guys don’t generate the greenhouse gas that contributes to global warming, according to researchers in the issue on April 23rd of Nature Communications.

“Microorganisms are the most diverse and abundant form of life on Earth, and we only know about 1% of them,” says Valerie De Anda, a University of Texas at Austin environmental microbiologist. “Our information is skewed in favour of organisms that are harmful to humans. However, numerous organisms drive the Earth’s major chemical cycles that we are unaware of.”

Archaea are an incredibly enigmatic group. They were not recognized as a distinct domain of life until the late 1970s, separate from bacteria and eukaryotes (which include everything else, from fungi to animals to plants).

For many years, archaea were believed to exist exclusively in Earth’s most extreme environments, such as hot springs. However, archaea are ubiquitous, and these microbes can significantly impact how carbon and nitrogen cycle between the Earth’s land, oceans, and atmosphere.

De Anda and her colleagues have discovered an entirely new archaea species — a large branch of related organisms on the tree of life. The first evidence of these unique organisms was sediments from seven hot springs in China and deep-sea hydrothermal vents in the Gulf of California’s Guaymas Basin. The team discovered bits of DNA in these sediments, which they meticulously assembled into the genetic blueprints, or genomes, of 15 different archaea.

De Anda and her colleagues have now discovered an entirely new species of archaea — a large branch of related organisms on the tree of life. These new organisms were found in sediments from seven hot springs in China and deep-sea hydrothermal vents in the Gulf of California’s Guaymas Basin. The team discovered DNA fragments in these sediments and meticulously assembled them into the genetic blueprints, or genomes, of 15 different archaea.

Brockarchaeota, it turns out, are found throughout the world — but they have been overlooked, undescribed, and unnamed until now. After piecing together the new genomes and searching public databases for them, De Anda and her colleagues discovered that fragments of these previously unknown organisms had been found in hot springs, geothermal, and hydrothermal vent sediments from South Africa to Indonesia to Rwanda.

The team also looked for genes related to the microbes’ metabolism — what nutrients they consume and what waste they produce — within the new genomes. Initially, the team anticipated that these archaea would be methane producers, similar to other archaea previously discovered in such environments. They consume the same materials as archaea that produce methane: one-carbon compounds such as methanol or methyl sulphide. “However, we were unable to identify the genes responsible for methane production,” De Anda explains. “They are absent from Brockarchaeota.”

This implies that these archaea must possess a previously unknown metabolism capable of recycling carbon — for example, in seafloor sediments — without producing methane. And, given their widespread distribution, De Anda speculates that these organisms may be playing a previously unnoticed but critical role in the Earth’s carbon cycle.

“It’s intriguing on two levels — it’s a new phylum and a novel metabolism,” says

“There is a lot out there,” De Anda explains. And “as you sequence more DNA, you realize that there is more out there that you couldn’t see the first time.”

Journal Reference:

De Anda, V., Chen, LX., Dombrowski, N. , Hua Z-S, Jiang H-C, Banfield JF, Li W-J, Baker BJ. Brockarchaeota, a novel archaeal phylum with unique and versatile carbon cycling pathways. Nat Commun 12, 2404 (2021). https://doi.org/10.1038/s41467-021-22736-6

Image Credit: Greg Willis