Valerie De Anda, an environmental microbiologist at the University of Texas in Austin, says, "Micro-organisms are the world's diverse and richest life, and we know only 1 percent of them. "The information we provide is oriented towards human organisms. But there are a lot of organisms on Earth, which we don't know about the most important chemical cycles."
A particular mysterious group is Archaea (SN: 14/220). They were recognized not until the late 1970s as the third area of life, separate from bacteria and eukaryotes (which include everything else, from fungi to animals to plants).
For many years, only in extreme environments such as hot springs on earth have archaea been believed to exist. However, Archaea is indeed everywhere; these microbes can be of major importance in the cycle between the soil, the oceans, and the atmosphere of carbon and nitrogen. The most abundant microbes in the sea are one group of archaea, Thaumarchaeota, said De Anda (SN: 11/28/17). In cows' stomachs, methane archaea also cause animals into the atmosphere to burst large volumes of gas (SN: 11/18/15).
Now De Anda and her fellow students have identified a whole new phylum — a large branch on the tree of life — of archaea. Sediments from seven hot springs in China and deep-sea hydrothermal winds in the Guaymas Basin of the Gulf of California were among the first evidence of these new organisms. In these sediments, the team has found bits of DNA that have been carefully assembled into 15 different archaean genetic blueprints or genomes.
The investigators then compared the genetic data of the genomes to those of thousands of previously identified microbial genomes described in public databases. But "these sequences were entirely different from whatever we know," says De Anda.
For Thomas Brock, a microbiologist who was the first to produce archaea in the workshop and died in April, she and her colleagues gave the new group the name Brockarchaeota. The discovery of Brock paved the way for the chain reaction of polymerases or PCR, a technique that won the Nobel Prize for small bits copying of DNA and that is currently used in COVID-19 tests (SN 3/6/20).
Brockarchaeota, it turns out, lives worldwide, but they have been ignored, undescribed and unnamed up until now. Once De Anda and her team have put new genomes together to hunt them in public databases, they have found bits of those formerly unknown organisms in sediments from South Africa to Indonesia to Rwanda in hot springs, geothermal and Hydrothermal ventilation.
The team has also chased genes linked to the metabolism of microbes within the new genomes — which nutrients they consume and what waste they produce. Initially, the team expected that these archaea would be methane producers, like other archaea previously found in such environments. They use one-carbon compounds, such as methanol or methyl sulfide, as a material used for methane production. "But the genes that produce methane cannot be identified," says De Anda. "In Brockarchaeota, they aren't there."
This means that these archaea have to have a previously undescribed metabolism by which carbon – in seabeds, for example – can be recycled without producing methane. And, given how widely spread, De Anda says, these organisms could play an important role in the Earth's carbon cycle, which has previously been covered.
The double is interesting — it is a new metabolism and phylum," says the Bozeman State University Montana's microbial ecologist Luke McKay. The fact that this entire group could have stayed for so long under the radar, he adds, "is an indication of where we are in the microbiological state."
But the discovery also testifies to the strength of the metagenomics, the technique used by researchers in a particular water or sediment sample, to divide individual genomes from a large hodgepodge of microbes. With this technology, scientists are increasingly identifying parts of the previously mysterious microbial world.
De Anda says, "There is so much out. And "every time you sequence more DNA, you begin to realize that you could not see the first time more."
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