No New Food Since the Dinosaur Era: A Story of Extreme Survival

Last week, scientists announced an intriguing discovery - bacteria that are slowly eking out a living deep beneath the ocean floor. The researchers raise the possibility that the organisms are more than a million years old. Since the findings were published in the journal Science, many people wrote about it, but the clearest and most engaging story I saw appeared in the Washington Post. You can read the whole story here.

Call it survival of the slowest: Extraordinarily old, bizarrely low-key bacteria have been found in sediments 100 feet below the sea floor of the Pacific Ocean, far removed from sunlight, fresh nutrients and what humans would consider anything interesting to do.

Some of these organisms, scientists say, could be at least 1,000 years old. Or maybe millions of years.

Their strategy for staying alive is to be barely alive at all. Their metabolism is dialed down to almost nothing, an adaptive advantage in a place with so few resources. The bacteria that survive are the ones that can satisfy themselves with minute traces of oxygen and a parsimonious diet of organic material laid down millions of years ago.

I love the use of the term “parsimonious diet”. Here’s a quote from the lead researcher, Hans Roy, a biologist at Aarhus University:

“These communities have not received input or new food since the dinosaurs walked the planet,” Roy said. “Those that are left down there are the ones that can deal with the lowest amount of food.”

The scientists haven’t figured out a way to measure the age of these organisms. Bacteria don't show their age the way we humans do. That’s a bit frustrating but the story is written with beautiful honesty and clarity by one of my all-time favorite science writers, Joel Achenbach. I’ve been a fan of his since I read an anthology of his “Why Things Are” columns back in the early 1990s. Here’s how he handles the uncertainty:

Key questions remain: How rapidly do these bacteria reproduce? Have they evolved and developed new traits in these eons in the subsea muck, or do they survive thanks to traits that were already there when they first inhabited the sea floor?

And how old are they, exactly?

It’s a big number, the scientists think.

“The notion of being several thousand years old is really a minimum of what is going on,” Hoehler ventured.

One possibility is that, over time, these bacteria have slowly reproduced, and thus today’s population is countless generations removed from the original population. But another idea is that the bacteria are in­cred­ibly old and are the last, hardy remnants of the population that flourished when the sediments first settled on the sea floor.

This is the kind of finding that informs the search for life elsewhere in the cosmos. We are still discovering what's possible for extreme life forms here on Earth.