Earth's simplest organisms are part of the food chain after all

Archaea are some of the most abundant and least understood, organisms on the planet. These single-celled creatures weren't even properly discovered until the 1970s, and big questions about them remain unanswered, such as whether other organisms ever eat them.

That might seem like the sort of thing we can take for granted - of course all organisms are part of the food chain somewhere along the line. But there's never been any evidence to actually prove that archaea form part of the diet of any larger organisms...until now. New research from Andrew Thurber and his team at Oregon State has found the first conclusive evidence that, yes, archaea can be good to eat.

These single-celled organisms form one of the three vast domains of life, with bacteria representing another and everything else - including all plants and animals - being grouped together as eukaryotes in the third domain. Various archaea species serve many vital functions in keeping ecosystems running smoothly, perhaps none more important than consuming the methane gas that would otherwise wreck marine environments.

It's that task that allowed Thurber and his team to confirm archaea are in fact eaten. Their studies of worms - like the one pictured up top - living near a deep sea cold seep off of Costa Rica showed the isotopic signatures of methane gas. The worms could not have ingested this gas directly - instead, it must have been brought in by archaea that they ad consumed. These worms are the first known "archivores", and it's thought that worms like these use their teeth to scrape archaea off the deep sea rocks.

And it appears the archaea actually do have some nutritional value for the worms. The researchers also undertook a laboratory study in which different worms had to subsist on different food sources, one of which was archaea. The archaea-fed worms did just as well as all their counterparts. In a statement, Thurber explained how this discovery is just the beginning of a new chapter in our understanding of these simple but crucial organisms:

"This opens up a new avenue of research. Archaea weren't even discovered until 1977, and were thought to be rare and unimportant, but we are beginning to realize that they not only are abundant, but they have roles that have not fully been appreciated.

"[These experiments] showed us that Archaea can be a viable food source for at least some animals. It could be that many other animals are consuming Archaea but we haven't been able to detect it. We still haven't found the right technique to identify animals that eat Archaea that don't rely on methane, but now we know to look. We're not yet sure of the implications. But Archaea are found in many different places, from estuaries to the deep sea, so it is possible that they fit into food webs beyond the cold seeps where we documented the process."

For more, check out the team's original paper at The ISME Journal.

Photo courtesy of Andrew Thurber, Oregon State University.