IN DECEMBER 2009, a submarine plunged 2,000 meters into the Gulf of California and emerged clutching a whole new branch of life. The deep-sea craft had not uncovered a new species of fish, or some hitherto unknown crustacean, but something much more profound. In one of the most alien environments on Earth, the submarine had found a group of microbes utterly distinct from all other life. In animal terms, it was like stumbling across mollusks or insects for the first time. Not just one new species but a whole swath of life had swum into focus.
This might sound momentous. It is momentous. But for Brett Baker, a microbial ecologist at the University of Texas at Austin, adding mighty branches to the tree of life is a fairly common occurrence. When he analyzes a deep-sea sample for the first time, just five out of every 200 genomes might already be known to science. In other samples taken from the ocean floor close to hydrothermal vents, he has found dozens of new microbial groups that no one has identified before. Each of them is a new piece in a puzzle of life that so far we can only see the edges of.
Baker named the group of deep-sea microbes collected in 2009 Helarchaeota — after the Norse goddess of the underworld. These microbes joined other groups named after Norse gods: Lokiarchaeota, Thorarchaeota, and Odinarchaeota. “We like these names because they’re easy to remember and they’re charismatic, right? Microbes usually aren’t charismatic, so giving them these names as it relates to their evolutionary history or their environments, it’s more fun, it’s more interesting, ”says Baker.
There is just one problem. Baker’s names, well, they kinda break every rule of naming microbial species. From a certain point of view, the organisms that Baker has technically discovered do not exist at all. They occupy a strange microbial hinterland: Species that are out there somewhere but are so strange and novel that they don’t quite fit into the scheme humans use to name microbes. Officially speaking, Helarchaeota falls into a category called Candidatus—A designation reserved for microbes that haven’t earned a proper scientific name yet.
“We are finding new kinds of life right and left,” says Karen Lloyd, a microbial ecologist at the University of Tennessee, Knoxville. But as more and more newly discovered microbes fall afoul of these naming rules, the result is a scientific snafu that is dividing microbiologists into two camps: Those who think it’s time to drag naming rules into the era of genomics and those who are worried that such a move would plunge the field into chaos. Within the small world of microbial naming, the winds of change are blowing, and not everyone is happy about it.
TO REALLY UNDERSTAND the predicament Lloyd and Baker are facing, there’s one thing you need to know about how species get their scientific names. In taxonomy — the field of biology that deals with naming and organizing life — it’s really important to be able to point to a physical specimen that represents a given species. Think you’ve seen a Carduelis carduelis (European goldfinch)? Open a dusty drawer inside the Natural History Museum’s storage facility just outside of London and you’ll find a dead bird with a tag around its ankle affirming that scientists agree that this specimen really is Carduelis carduelis. Other species are represented by fossils, or drawings, but generally to have a scientific name an animal must be represented by what zoologists call a “type” —a physical thing that is tied to that species. (The type for Homo sapiensby the way, is the skeleton of Carl Linnaeus, the 18th-century Swedish zoologist who kicked off the whole field of taxonomy. Inconveniently, those bones are buried beneath the floor of Uppsala Cathedral in Sweden.)